Hyoscyamine, Atropine, Scopolamine, and Phenobarbital

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product.

Elixir, Oral:

Donnatal: Hyoscyamine sulfate 0.1037 mg, atropine sulfate 0.0194 mg, scopolamine hydrobromide 0.0065 mg, and phenobarbital 16.2 mg per 5 mL (120 mL, 480 mL) [contains ethanol <23.8%; grape flavor]

Donnatal: Hyoscyamine sulfate 0.1037 mg, atropine sulfate 0.0194 mg, scopolamine hydrobromide 0.0065 mg, and phenobarbital 16.2 mg per 5 mL (120 mL, 480 mL) [contains ethanol <23.8%, tartrazine; mint flavor]

Tablet, Oral:

Donnatal: Hyoscyamine sulfate 0.1037 mg, atropine sulfate 0.0194 mg, scopolamine hydrobromide 0.0065 mg, and phenobarbital 16.2 mg

Phenohytro: Hyoscyamine sulfate 0.1037 mg, atropine sulfate 0.0194 mg, scopolamine hydrobromide 0.0065 mg, and phenobarbital 16.2 mg

Tablet, extended release, Oral:

Donnatal Extentabs: Hyoscyamine sulfate 0.3111 mg, atropine sulfate 0.0582 mg, scopolamine hydrobromide 0.0195 mg, and phenobarbital 48.6 mg [DSC]

Anticholinergic agents (hyoscyamine, atropine, and scopolamine) inhibit the muscarinic actions of acetylcholine at the postganglionic parasympathetic neuroeffector sites including smooth muscle, secretory glands, and CNS sites; specific anticholinergic responses are dose-related.

Absorption

Well absorbed from the GI tract

Oral: Do not crush extended release tablets.

Abiraterone Acetate: CYP3A4 Inducers (Strong) may decrease the serum concentration of Abiraterone Acetate. Management: Avoid whenever possible. If such a combination cannot be avoided, increase abiraterone acetate dosing frequency from once daily to twice daily during concomitant use. Avoid combination

AbobotulinumtoxinA: Anticholinergic Agents may enhance the anticholinergic effect of AbobotulinumtoxinA. Monitor therapy

Acetaminophen: Barbiturates may increase the metabolism of Acetaminophen. This may 1) diminish the effect of acetaminophen; and 2) increase the risk of liver damage. Monitor therapy

Acetylcholinesterase Inhibitors: Anticholinergic Agents may diminish the therapeutic effect of Acetylcholinesterase Inhibitors. Acetylcholinesterase Inhibitors may diminish the therapeutic effect of Anticholinergic Agents. Monitor therapy

Aclidinium: May enhance the anticholinergic effect of Anticholinergic Agents. Avoid combination

Afatinib: PHENobarbital may decrease the serum concentration of Afatinib. Management: Per US labeling: if requiring chronic use of phenobarbital, increase afatinib dose by 10 mg as tolerated; reduce to original afatinib dose 2-3 days after stopping phenobarbital. Per Canadian labeling: avoid combination if possible. Consider therapy modification

Albendazole: PHENobarbital may decrease serum concentrations of the active metabolite(s) of Albendazole. Monitor therapy

Alcohol (Ethyl): CNS Depressants may enhance the CNS depressant effect of Alcohol (Ethyl). Monitor therapy

Amantadine: May enhance the anticholinergic effect of Anticholinergic Agents. Monitor therapy

Amifampridine: May diminish the anticholinergic effect of Anticholinergic Agents. Anticholinergic Agents may diminish the therapeutic effect of Amifampridine. Monitor therapy

Amphetamines: May decrease the serum concentration of PHENobarbital. Monitor therapy

Analgesics (Opioid): CNS Depressants may enhance the CNS depressant effect of Analgesics (Opioid). Management: Avoid concomitant use of opioid analgesics and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug. Consider therapy modification

Antacids: May decrease the serum concentration of Hyoscyamine. Management: Administer immediate release hyoscyamine before meals and antacids after meals when these agents are given in combination. Consider therapy modification

Anticholinergic Agents: May enhance the adverse/toxic effect of other Anticholinergic Agents. Monitor therapy

Antihepaciviral Combination Products: CYP3A4 Inducers (Strong) may decrease the serum concentration of Antihepaciviral Combination Products. Avoid combination

Apixaban: CYP3A4 Inducers (Strong) may decrease the serum concentration of Apixaban. Avoid combination

Apremilast: CYP3A4 Inducers (Strong) may decrease the serum concentration of Apremilast. Avoid combination

Aprepitant: CYP3A4 Inducers (Strong) may decrease the serum concentration of Aprepitant. Avoid combination

ARIPiprazole: CYP3A4 Inducers (Strong) may decrease the serum concentration of ARIPiprazole. Management: Double the oral aripiprazole dose and closely monitor. Reduce oral aripiprazole dose to 10-15 mg/day (for adults) if the inducer is discontinued. Avoid use of strong CYP3A4 inducers for more than 14 days with extended-release injectable aripiprazole. Consider therapy modification

ARIPiprazole Lauroxil: CYP3A4 Inducers (Strong) may decrease serum concentrations of the active metabolite(s) of ARIPiprazole Lauroxil. Management: Patients taking the 441 mg dose of aripiprazole lauroxil increase their dose to 662 mg if used with a strong CYP3A4 inducer for more than 14 days. No dose adjustment is necessary for patients using the higher doses of aripiprazole lauroxil. Consider therapy modification

Artemether: CYP3A4 Inducers (Strong) may decrease serum concentrations of the active metabolite(s) of Artemether. Specifically, dihydroartemisinin concentrations may be reduced. CYP3A4 Inducers (Strong) may decrease the serum concentration of Artemether. Avoid combination

Asunaprevir: CYP3A4 Inducers (Strong) may decrease the serum concentration of Asunaprevir. Avoid combination

Axitinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Axitinib. Avoid combination

Azelastine (Nasal): CNS Depressants may enhance the CNS depressant effect of Azelastine (Nasal). Avoid combination

Bazedoxifene: PHENobarbital may decrease the serum concentration of Bazedoxifene. This may lead to loss of efficacy or, if bazedoxifene is combined with estrogen therapy, an increased risk of endometrial hyperplasia. Monitor therapy

Bedaquiline: CYP3A4 Inducers (Strong) may decrease the serum concentration of Bedaquiline. Avoid combination

Benperidol: CYP3A4 Inducers (Strong) may decrease the serum concentration of Benperidol. Monitor therapy

Beta-Blockers: Barbiturates may decrease the serum concentration of Beta-Blockers. Exceptions: Atenolol; Levobunolol; Metipranolol; Nadolol. Monitor therapy

Blonanserin: CNS Depressants may enhance the CNS depressant effect of Blonanserin. Consider therapy modification

Blood Pressure Lowering Agents: Barbiturates may enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Boceprevir: PHENobarbital may decrease the serum concentration of Boceprevir. Avoid combination

Bortezomib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Bortezomib. Avoid combination

Bosutinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Bosutinib. Avoid combination

Brentuximab Vedotin: CYP3A4 Inducers (Strong) may decrease the serum concentration of Brentuximab Vedotin. Specifically, concentrations of the active monomethyl auristatin E (MMAE) component may be decreased. Monitor therapy

Brexpiprazole: CYP3A4 Inducers (Strong) may decrease the serum concentration of Brexpiprazole. Management: If brexpiprazole is used together with a strong CYP3A4 inducer, the brexpiprazole dose should gradually be doubled over the course of 1 to 2 weeks. Consider therapy modification

Brigatinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Brigatinib. Avoid combination

Brimonidine (Topical): May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Buprenorphine: CNS Depressants may enhance the CNS depressant effect of Buprenorphine. Management: Consider reduced doses of other CNS depressants, and avoiding such drugs in patients at high risk of buprenorphine overuse/self-injection. Initiate buprenorphine patches (Butrans brand) at 5 mcg/hr in adults when used with other CNS depressants. Consider therapy modification

Cabozantinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Cabozantinib. Management: Avoid use of strong CYP3A4 inducers with cabozantinib if possible. If combined, cabozantinib dose adjustments are recommended and vary based on the cabozantinib product used and the indication for use. See monograph for details. Consider therapy modification

Calcifediol: CYP3A4 Inducers (Strong) may decrease the serum concentration of Calcifediol. Monitor therapy

Calcium Channel Blockers: Barbiturates may increase the metabolism of Calcium Channel Blockers. Management: Monitor for decreased therapeutic effects of calcium channel blockers with concomitant barbiturate therapy. Calcium channel blocker dose adjustments may be necessary. Nimodipine Canadian labeling contraindicates concomitant use with phenobarbital. Exceptions: Clevidipine. Monitor therapy

Canagliflozin: PHENobarbital may decrease the serum concentration of Canagliflozin. Management: Consider increasing canagliflozin dose to 300 mg/day in patients with estimated GFR >60 mL/min/1.73 m2 who tolerate canagliflozin 100 mg/day and require greater glycemic control. Consider alternatives in patients with estimated GFR 45-60 mL/min/1.73 m2. Consider therapy modification

Cannabidiol: CYP3A4 Inducers (Strong) may decrease the serum concentration of Cannabidiol. Monitor therapy

Cannabis: CYP3A4 Inducers (Strong) may decrease the serum concentration of Cannabis. More specifically, tetrahydrocannabinol and cannabidiol serum concentrations may be decreased. Monitor therapy

Cannabis: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Cariprazine: CYP3A4 Inducers (Strong) may decrease the serum concentration of Cariprazine. Avoid combination

Ceritinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Ceritinib. Avoid combination

Chloral Betaine: May enhance the adverse/toxic effect of Anticholinergic Agents. Monitor therapy

Chloramphenicol: May decrease the metabolism of Barbiturates. Barbiturates may increase the metabolism of Chloramphenicol. Consider therapy modification

Chlormethiazole: May enhance the CNS depressant effect of CNS Depressants. Management: Monitor closely for evidence of excessive CNS depression. The chlormethiazole labeling states that an appropriately reduced dose should be used if such a combination must be used. Consider therapy modification

Chlorphenesin Carbamate: May enhance the adverse/toxic effect of CNS Depressants. Monitor therapy

Cholestyramine Resin: May decrease the serum concentration of PHENobarbital. Management: Administer phenobarbital at least 1 hour before or 4-6 hours after administration of cholestyramine in order to minimize the risk for any significant interaction. Consider therapy modification

Cimetropium: Anticholinergic Agents may enhance the anticholinergic effect of Cimetropium. Avoid combination

Clarithromycin: CYP3A4 Inducers (Strong) may increase serum concentrations of the active metabolite(s) of Clarithromycin. Clarithromycin may increase the serum concentration of CYP3A4 Inducers (Strong). CYP3A4 Inducers (Strong) may decrease the serum concentration of Clarithromycin. Management: Consider alternative antimicrobial therapy for patients receiving a CYP3A inducer. Drugs that enhance the metabolism of clarithromycin into 14-hydroxyclarithromycin may alter the clinical activity of clarithromycin and may impair clarithromycin efficacy. Consider therapy modification

Clindamycin (Systemic): CYP3A4 Inducers (Strong) may decrease the serum concentration of Clindamycin (Systemic). Refer to the specific clindamycin (systemic) - rifampin drug interaction monograph for information concerning that combination. Monitor therapy

CloZAPine: CYP3A4 Inducers (Strong) may decrease the serum concentration of CloZAPine. Avoid combination

CNS Depressants: May enhance the adverse/toxic effect of other CNS Depressants. Monitor therapy

Cobicistat: PHENobarbital may decrease the serum concentration of Cobicistat. Avoid combination

Cobimetinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Cobimetinib. Avoid combination

Contraceptives (Estrogens): Barbiturates may diminish the therapeutic effect of Contraceptives (Estrogens). Contraceptive failure is possible. Management: Use of a non-hormonal contraceptive is recommended. Consider therapy modification

Contraceptives (Progestins): Barbiturates may diminish the therapeutic effect of Contraceptives (Progestins). Contraceptive failure is possible. Management: Use of alternative, nonhormonal contraceptives is recommended. Consider therapy modification

Corticosteroids (Systemic): CYP3A4 Inducers (Strong) may decrease the serum concentration of Corticosteroids (Systemic). Exceptions: Hydrocortisone (Systemic); PrednisoLONE (Systemic); PredniSONE. Monitor therapy

Cosyntropin: May enhance the hepatotoxic effect of PHENobarbital. Monitor therapy

Crizotinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Crizotinib. Avoid combination

CycloSPORINE (Systemic): Barbiturates may increase the metabolism of CycloSPORINE (Systemic). Consider therapy modification

CYP2A6 Substrates: CYP2A6 Inducers (Strong) may increase the metabolism of CYP2A6 Substrates. Management: Consider an alternative for one of the interacting drugs. Some combinations may be specifically contraindicated. Consult appropriate manufacturer labeling. Consider therapy modification

CYP2C19 Inducers (Strong): May increase the metabolism of CYP2C19 Substrates. Management: Consider an alternative for one of the interacting drugs. Some combinations may be specifically contraindicated. Consult appropriate manufacturer labeling. Consider therapy modification

CYP2C19 Inhibitors (Moderate): May decrease the metabolism of CYP2C19 Substrates. Monitor therapy

CYP2C19 Inhibitors (Strong): May decrease the metabolism of CYP2C19 Substrates. Consider therapy modification

CYP2C8 Substrates: CYP2C8 Inducers (Strong) may increase the metabolism of CYP2C8 Substrates. Management: Consider an alternative for one of the interacting drugs. Some combinations may be specifically contraindicated. Consult appropriate manufacturer labeling. Consider therapy modification

CYP2C9 Substrates: CYP2C9 Inducers (Strong) may increase the metabolism of CYP2C9 Substrates. Management: Consider an alternative for one of the interacting drugs. Some combinations may be specifically contraindicated. Consult appropriate manufacturer labeling. Consider therapy modification

CYP3A4 Substrates: CYP3A4 Inducers (Strong) may increase the metabolism of CYP3A4 Substrates. Management: Consider an alternative for one of the interacting drugs. Some combinations may be specifically contraindicated. Consult appropriate manufacturer labeling. Exceptions: Buprenorphine; Etizolam; HYDROcodone; Zolpidem. Consider therapy modification

Dabrafenib: May decrease the serum concentration of CYP2C19 Substrates. Management: Seek alternatives to the CYP2C19 substrate when possible. If concomitant therapy cannot be avoided, monitor clinical effects of the substrate closely (particularly therapeutic effects). Consider therapy modification

Daclatasvir: CYP3A4 Inducers (Strong) may decrease the serum concentration of Daclatasvir. Avoid combination

Dapsone (Topical): May enhance the adverse/toxic effect of Methemoglobinemia Associated Agents. Monitor therapy

Darunavir: May decrease the serum concentration of PHENobarbital. Monitor therapy

Dasabuvir: CYP3A4 Inducers (Strong) may decrease the serum concentration of Dasabuvir. Avoid combination

Dasabuvir: CYP2C8 Inducers (Strong) may decrease the serum concentration of Dasabuvir. Avoid combination

Dasatinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Dasatinib. Management: Avoid when possible. If such a combination cannot be avoided, consider increasing dasatinib dose and monitor clinical response and toxicity closely. Consider therapy modification

Deferasirox: PHENobarbital may decrease the serum concentration of Deferasirox. Management: Avoid combination when possible; if the combination must be used, consider a 50% increase in initial deferasirox dose, with monitoring of serum ferritin concentrations and clinical responses to guide further dosing. Consider therapy modification

Deflazacort: CYP3A4 Inducers (Strong) may decrease serum concentrations of the active metabolite(s) of Deflazacort. Avoid combination

Delamanid: CYP3A4 Inducers (Strong) may decrease the serum concentration of Delamanid. Avoid combination

Dexamethasone (Systemic): CYP3A4 Inducers (Strong) may decrease the serum concentration of Dexamethasone (Systemic). Management: Consider dexamethasone dose increases in patients receiving strong CYP3A4 inducers and monitor closely for reduced steroid efficacy. Consider therapy modification

Dexmethylphenidate: May increase the serum concentration of PHENobarbital. Monitor therapy

Diclofenac (Systemic): CYP2C9 Inducers (Strong) may decrease the serum concentration of Diclofenac (Systemic). Monitor therapy

Dienogest: CYP3A4 Inducers (Strong) may decrease the serum concentration of Dienogest. Management: Avoid use of dienogest for contraception when using medications that induce CYP3A4 and for at least 28 days after discontinuation of a CYP3A4 inducer. An alternative form of contraception should be used during this time. Avoid combination

Diethylstilbestrol: CYP3A4 Inducers (Strong) may decrease the serum concentration of Diethylstilbestrol. Monitor therapy

Dimethindene (Topical): May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Disopyramide: PHENobarbital may decrease the serum concentration of Disopyramide. Monitor therapy

Dolutegravir: PHENobarbital may decrease the serum concentration of Dolutegravir. Avoid combination

Doxercalciferol: CYP3A4 Inducers (Strong) may increase serum concentrations of the active metabolite(s) of Doxercalciferol. Monitor therapy

DOXOrubicin (Conventional): CYP3A4 Inducers (Strong) may decrease the serum concentration of DOXOrubicin (Conventional). Management: Seek alternatives to strong CYP3A4 inducers in patients treated with doxorubicin. One U.S. manufacturer (Pfizer Inc.) recommends that these combinations be avoided. Consider therapy modification

Doxycycline: Barbiturates may decrease the serum concentration of Doxycycline. Consider therapy modification

Doxylamine: May enhance the CNS depressant effect of CNS Depressants. Management: The manufacturer of Diclegis (doxylamine/pyridoxine), intended for use in pregnancy, specifically states that use with other CNS depressants is not recommended. Monitor therapy

Dronabinol: CYP3A4 Inducers (Strong) may decrease the serum concentration of Dronabinol. Monitor therapy

Dronabinol: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Dronedarone: CYP3A4 Inducers (Strong) may decrease the serum concentration of Dronedarone. Avoid combination

Droperidol: May enhance the CNS depressant effect of CNS Depressants. Management: Consider dose reductions of droperidol or of other CNS agents (e.g., opioids, barbiturates) with concomitant use. Consider therapy modification

Eliglustat: CYP3A4 Inducers (Strong) may decrease the serum concentration of Eliglustat. Avoid combination

Eluxadoline: Anticholinergic Agents may enhance the constipating effect of Eluxadoline. Avoid combination

Elvitegravir: PHENobarbital may decrease the serum concentration of Elvitegravir. Avoid combination

Enzalutamide: CYP2C8 Inducers (Strong) may decrease the serum concentration of Enzalutamide. Avoid combination

Enzalutamide: CYP3A4 Inducers (Strong) may decrease the serum concentration of Enzalutamide. Management: Consider using an alternative agent that has no or minimal CYP3A4 induction potential when possible. If this combination cannot be avoided, increase the dose of enzalutamide from 160 mg daily to 240 mg daily. Avoid combination

EPHEDrine (Systemic): Atropine (Systemic) may enhance the therapeutic effect of EPHEDrine (Systemic). Monitor therapy

Erlotinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Erlotinib. Management: Avoid combination if possible. If combination must be used, increase erlotinib dose by 50 mg increments every 2 weeks as tolerated, to a maximum of 450 mg/day. Consider therapy modification

Eslicarbazepine: PHENobarbital may decrease the serum concentration of Eslicarbazepine. Monitor therapy

Estriol (Systemic): CYP3A4 Inducers (Strong) may decrease the serum concentration of Estriol (Systemic). Monitor therapy

Estriol (Topical): CYP3A4 Inducers (Strong) may decrease the serum concentration of Estriol (Topical). Monitor therapy

Etizolam: CYP3A4 Inducers (Strong) may decrease the serum concentration of Etizolam. Monitor therapy

Etoposide: CYP3A4 Inducers (Strong) may decrease the serum concentration of Etoposide. Management: When possible, seek alternatives to strong CYP3A4-inducing medications in patients receiving etoposide. If these combinations cannot be avoided, monitor patients closely for diminished etoposide response. Consider therapy modification

Etoposide Phosphate: CYP3A4 Inducers (Strong) may decrease the serum concentration of Etoposide Phosphate. Management: When possible, seek alternatives to strong CYP3A4-inducing medications in patients receiving etoposide phosphate. If these combinations cannot be avoided, monitor patients closely for diminished etoposide phosphate response. Consider therapy modification

Etravirine: PHENobarbital may decrease the serum concentration of Etravirine. Avoid combination

Everolimus: CYP3A4 Inducers (Strong) may decrease the serum concentration of Everolimus. Management: Avoid concurrent use of strong CYP3A4 inducers, but if strong CYP3A4 inducers cannot be avoided, consider gradually (in 5 mg increments) increasing the everolimus dose from 10 mg/day to 20 mg/day (adult doses). Avoid combination

Evogliptin: CYP3A4 Inducers (Strong) may decrease the serum concentration of Evogliptin. Monitor therapy

Exemestane: CYP3A4 Inducers (Strong) may decrease the serum concentration of Exemestane. Management: Exemestane U.S. product labeling recommends using an increased dose (50 mg/day) in patients receiving concurrent strong CYP3A4 inducers. The Canadian product labeling does not recommend a dose adjustment with concurrent use of strong CYP3A4 inducers. Consider therapy modification

Felbamate: PHENobarbital may decrease the serum concentration of Felbamate. Felbamate may increase the serum concentration of PHENobarbital. Management: In patients receiving phenobarbital, initiate felbamate at 1200 mg/day in divided doses 3-4 times daily and reduce phenobarbital dose by 20%. Monitor for increased phenobarbital concentrations/effects and decreased felbamate concentrations/effects. Consider therapy modification

Flibanserin: CYP3A4 Inducers (Strong) may decrease the serum concentration of Flibanserin. Avoid combination

Flunitrazepam: CNS Depressants may enhance the CNS depressant effect of Flunitrazepam. Consider therapy modification

Folic Acid: May decrease the serum concentration of PHENobarbital. Monitor therapy

Fosphenytoin: May enhance the CNS depressant effect of PHENobarbital. Fosphenytoin may increase the serum concentration of PHENobarbital. PHENobarbital may decrease the serum concentration of Fosphenytoin. Monitor therapy

Gastrointestinal Agents (Prokinetic): Anticholinergic Agents may diminish the therapeutic effect of Gastrointestinal Agents (Prokinetic). Monitor therapy

Gefitinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Gefitinib. Management: In the absence of severe adverse reactions, increase gefitinib dose to 500 mg daily in patients receiving strong CYP3A4 inducers; resume 250 mg dose 7 days after discontinuation of the strong inducer. Carefully monitor clinical response. Consider therapy modification

Gemigliptin: CYP3A4 Inducers (Strong) may decrease serum concentrations of the active metabolite(s) of Gemigliptin. CYP3A4 Inducers (Strong) may decrease the serum concentration of Gemigliptin. Avoid combination

Gestrinone: PHENobarbital may decrease the serum concentration of Gestrinone. Monitor therapy

Glecaprevir and Pibrentasvir: CYP3A4 Inducers (Strong) may decrease the serum concentration of Glecaprevir and Pibrentasvir. Monitor therapy

Glucagon: Anticholinergic Agents may enhance the adverse/toxic effect of Glucagon. Specifically, the risk of gastrointestinal adverse effects may be increased. Avoid combination

Glycopyrrolate (Oral Inhalation): Anticholinergic Agents may enhance the anticholinergic effect of Glycopyrrolate (Oral Inhalation). Avoid combination

Grazoprevir: CYP3A4 Inducers (Strong) may decrease the serum concentration of Grazoprevir. Avoid combination

Griseofulvin: Barbiturates may decrease the serum concentration of Griseofulvin. Monitor therapy

GuanFACINE: CYP3A4 Inducers (Strong) may decrease the serum concentration of GuanFACINE. Management: Increase the guanfacine dose by up to double when initiating concomitant therapy with strong CYP3A4 inducers. Increase guanfacine dose gradually over 1-2 weeks if strong CYP3A4 inducer therapy is just beginning. Consider therapy modification

Hemin: Barbiturates may diminish the therapeutic effect of Hemin. Avoid combination

HYDROcodone: CNS Depressants may enhance the CNS depressant effect of HYDROcodone. Management: Avoid concomitant use of hydrocodone and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug. Consider therapy modification

Hydrocortisone (Systemic): CYP3A4 Inducers (Strong) may decrease the serum concentration of Hydrocortisone (Systemic). Monitor therapy

HydrOXYzine: May enhance the CNS depressant effect of Barbiturates. Management: Consider a decrease in the barbiturate dose, as appropriate, when used together with hydroxyzine. With concurrent use, monitor patients closely for excessive response to the combination. Consider therapy modification

Ibrutinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Ibrutinib. Avoid combination

Idelalisib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Idelalisib. Avoid combination

Ifosfamide: CYP3A4 Inducers (Strong) may increase serum concentrations of the active metabolite(s) of Ifosfamide. CYP3A4 Inducers (Strong) may decrease serum concentrations of the active metabolite(s) of Ifosfamide. Monitor therapy

Imatinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Imatinib. Management: Avoid concurrent use of imatinib with strong CYP3A4 inducers when possible. If such a combination must be used, increase imatinib dose by at least 50% and monitor the patient's clinical response closely. Consider therapy modification

Ipratropium (Oral Inhalation): May enhance the anticholinergic effect of Anticholinergic Agents. Avoid combination

Irinotecan Products: CYP3A4 Inducers (Strong) may decrease serum concentrations of the active metabolite(s) of Irinotecan Products. Specifically, serum concentrations of SN-38 may be reduced. CYP3A4 Inducers (Strong) may decrease the serum concentration of Irinotecan Products. Avoid combination

Isavuconazonium Sulfate: CYP3A4 Inducers (Strong) may decrease serum concentrations of the active metabolite(s) of Isavuconazonium Sulfate. Specifically, CYP3A4 Inducers (Strong) may decrease isavuconazole serum concentrations. Avoid combination

Itopride: Anticholinergic Agents may diminish the therapeutic effect of Itopride. Monitor therapy

Itraconazole: CYP3A4 Inducers (Strong) may decrease the serum concentration of Itraconazole. Avoid combination

Ivabradine: CYP3A4 Inducers (Strong) may decrease the serum concentration of Ivabradine. Avoid combination

Ivacaftor: CYP3A4 Inducers (Strong) may decrease the serum concentration of Ivacaftor. Avoid combination

Ixabepilone: CYP3A4 Inducers (Strong) may decrease the serum concentration of Ixabepilone. Management: Avoid this combination whenever possible. If this combination must be used, a gradual increase in ixabepilone dose from 40 mg/m2 to 60 mg/m2 (given as a 4-hour infusion), as tolerated, should be considered. Consider therapy modification

Ixazomib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Ixazomib. Avoid combination

Kava Kava: May enhance the adverse/toxic effect of CNS Depressants. Monitor therapy

Lacosamide: PHENobarbital may decrease the serum concentration of Lacosamide. Monitor therapy

LamoTRIgine: Barbiturates may decrease the serum concentration of LamoTRIgine. Management: See lamotrigine prescribing information for specific age-dependent dosing guidelines regarding concurrent use with a barbiturate, as well as for adjusting lamotrigine dosing if concurrent barbiturate therapy is discontinued. Consider therapy modification

Lapatinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Lapatinib. Management: If therapy overlap cannot be avoided, consider titrating lapatinib gradually from 1,250 mg/day up to 4,500 mg/day (HER2 positive metastatic breast cancer) or 1,500 mg/day up to 5,500 mg/day (hormone receptor/HER2 positive breast cancer) as tolerated. Avoid combination

Ledipasvir: PHENobarbital may decrease the serum concentration of Ledipasvir. Avoid combination

Leucovorin Calcium-Levoleucovorin: May decrease the serum concentration of PHENobarbital. Monitor therapy

Levomefolate: May decrease the serum concentration of PHENobarbital. Monitor therapy

Levosulpiride: Anticholinergic Agents may diminish the therapeutic effect of Levosulpiride. Avoid combination

Linagliptin: CYP3A4 Inducers (Strong) may decrease the serum concentration of Linagliptin. Management: Strongly consider using an alternative to any strong CYP3A4 inducer in patients who are being treated with linagliptin. If this combination is used, monitor patients closely for evidence of reduced linagliptin effectiveness. Consider therapy modification

Lofexidine: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Lopinavir: PHENobarbital may decrease the serum concentration of Lopinavir. Management: Increased doses of lopinavir may be necessary when using these agents in combination. Do not use a once daily lopinavir/ritonavir regimen together with phenobarbital. Increase monitoring of therapeutic response in all patients using this combination. Consider therapy modification

Lumacaftor: May decrease the serum concentration of CYP2C19 Substrates. Monitor therapy

Lumefantrine: CYP3A4 Inducers (Strong) may decrease the serum concentration of Lumefantrine. Avoid combination

Lurasidone: CYP3A4 Inducers (Strong) may decrease the serum concentration of Lurasidone. Avoid combination

Macitentan: CYP3A4 Inducers (Strong) may decrease the serum concentration of Macitentan. Avoid combination

Magnesium Sulfate: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Manidipine: CYP3A4 Inducers (Strong) may decrease the serum concentration of Manidipine. Management: Consider avoiding concomitant use of manidipine and strong CYP3A4 inducers. If combined, monitor closely for decreased manidipine effects and loss of efficacy. Increased manidipine doses may be required. Consider therapy modification

Maraviroc: CYP3A4 Inducers (Strong) may decrease the serum concentration of Maraviroc. Management: Increase maraviroc adult dose to 600 mg twice daily when used with strong CYP3A4 inducers. This does not apply to patients also receiving strong CYP3A4 inhibitors. Do not use maraviroc with strong CYP3A4 inducers in patients with CrCl less than 30 mL/min. Consider therapy modification

Mefloquine: May diminish the therapeutic effect of Anticonvulsants. Mefloquine may decrease the serum concentration of Anticonvulsants. Management: Mefloquine is contraindicated for malaria prophylaxis in persons with a history of convulsions. Monitor anticonvulsant concentrations and treatment response closely with concurrent use. Consider therapy modification

Methotrimeprazine: May enhance the CNS depressant effect of CNS Depressants. CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. Management: Reduce adult dose of CNS depressant agents by 50% with initiation of concomitant methotrimeprazine therapy. Further CNS depressant dosage adjustments should be initiated only after clinically effective methotrimeprazine dose is established. Consider therapy modification

Methoxyflurane: Barbiturates may enhance the nephrotoxic effect of Methoxyflurane. Barbiturates may increase the metabolism of Methoxyflurane. Avoid combination

Methylfolate: May decrease the serum concentration of PHENobarbital. Monitor therapy

Methylphenidate: May increase the serum concentration of PHENobarbital. Monitor therapy

MethylPREDNISolone: CYP3A4 Inducers (Strong) may decrease the serum concentration of MethylPREDNISolone. Management: Consider methylprednisolone dose increases in patients receiving strong CYP3A4 inducers and monitor closely for reduced steroid efficacy. Consider therapy modification

MetroNIDAZOLE (Systemic): PHENobarbital may decrease the serum concentration of MetroNIDAZOLE (Systemic). Monitor therapy

MetyroSINE: CNS Depressants may enhance the sedative effect of MetyroSINE. Monitor therapy

Mianserin: May enhance the CNS depressant effect of Barbiturates. Mianserin may diminish the therapeutic effect of Barbiturates. Barbiturates may decrease the serum concentration of Mianserin. Avoid combination

Midostaurin: CYP3A4 Inducers (Strong) may decrease the serum concentration of Midostaurin. Avoid combination

MiFEPRIStone: CYP3A4 Inducers (Strong) may decrease the serum concentration of MiFEPRIStone. Avoid combination

Minocycline: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Mirabegron: Anticholinergic Agents may enhance the adverse/toxic effect of Mirabegron. Monitor therapy

Mirodenafil: CYP3A4 Inducers (Strong) may decrease the serum concentration of Mirodenafil. Management: Consider avoiding the concomitant use of mirodenafil and strong CYP3A4 inducers. If combined, monitor for decreased mirodenafil effects. Mirodenafil dose increases may be required to achieve desired effects. Consider therapy modification

Multivitamins/Minerals (with ADEK, Folate, Iron): May decrease the serum concentration of Barbiturates. Monitor therapy

Nabilone: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Naldemedine: CYP3A4 Inducers (Strong) may decrease the serum concentration of Naldemedine. Avoid combination

Nalmefene: PHENobarbital may decrease the serum concentration of Nalmefene. Monitor therapy

Naloxegol: CYP3A4 Inducers (Strong) may decrease the serum concentration of Naloxegol. Avoid combination

Neratinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Neratinib. Avoid combination

Netupitant: CYP3A4 Inducers (Strong) may decrease the serum concentration of Netupitant. Avoid combination

NIFEdipine: CYP3A4 Inducers (Strong) may decrease the serum concentration of NIFEdipine. Avoid combination

Nilotinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Nilotinib. Avoid combination

NiMODipine: CYP3A4 Inducers (Strong) may decrease the serum concentration of NiMODipine. Avoid combination

Nisoldipine: CYP3A4 Inducers (Strong) may decrease the serum concentration of Nisoldipine. Avoid combination

Nitric Oxide: May enhance the adverse/toxic effect of Methemoglobinemia Associated Agents. Combinations of these agents may increase the likelihood of significant methemoglobinemia. Management: Monitor patients for signs of methemoglobinemia (e.g., hypoxia, cyanosis) when nitric oxide is used in combination with other agents associated with development of methemoglobinemia. Avoid lidocaine/prilocaine. Monitor therapy

Nitroglycerin: Anticholinergic Agents may decrease the absorption of Nitroglycerin. Specifically, anticholinergic agents may decrease the dissolution of sublingual nitroglycerin tablets, possibly impairing or slowing nitroglycerin absorption. Monitor therapy

Olaparib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Olaparib. Avoid combination

Ombitasvir, Paritaprevir, Ritonavir, and Dasabuvir: CYP2C8 Inducers (Strong) may decrease the serum concentration of Ombitasvir, Paritaprevir, Ritonavir, and Dasabuvir. Specifically, the serum concentrations of dasabuvir may decrease significantly. Avoid combination

OnabotulinumtoxinA: Anticholinergic Agents may enhance the anticholinergic effect of OnabotulinumtoxinA. Monitor therapy

Orlistat: May decrease the serum concentration of Anticonvulsants. Monitor therapy

Orphenadrine: CNS Depressants may enhance the CNS depressant effect of Orphenadrine. Avoid combination

Osimertinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Osimertinib. Consider therapy modification

Oxatomide: May enhance the anticholinergic effect of Anticholinergic Agents. Avoid combination

OXcarbazepine: PHENobarbital may decrease serum concentrations of the active metabolite(s) of OXcarbazepine. Specifically, concentrations of the major active 10-monohydroxy metabolite may be reduced. OXcarbazepine may increase the serum concentration of PHENobarbital. Management: Consider increasing the initial adult oxcarbazepine extended release tablet (Oxtellar XR) dose to 900 mg/day. No specific recommendations are available for other oxcarbazepine formulations. Consider therapy modification

Oxomemazine: May enhance the CNS depressant effect of CNS Depressants. Avoid combination

OxyCODONE: CNS Depressants may enhance the CNS depressant effect of OxyCODONE. Management: Avoid concomitant use of oxycodone and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug. Consider therapy modification

Palbociclib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Palbociclib. Avoid combination

Panobinostat: CYP3A4 Inducers (Strong) may decrease the serum concentration of Panobinostat. Avoid combination

Paraldehyde: CNS Depressants may enhance the CNS depressant effect of Paraldehyde. Avoid combination

PAZOPanib: CYP3A4 Inducers (Strong) may decrease the serum concentration of PAZOPanib. Avoid combination

Perampanel: CYP3A4 Inducers (Strong) may decrease the serum concentration of Perampanel. Management: Increase the perampanel starting dose to 4 mg/day when perampanel is used concurrently with moderate and strong CYP3A4 inducers. Consider therapy modification

Perampanel: May enhance the CNS depressant effect of CNS Depressants. Management: Patients taking perampanel with any other drug that has CNS depressant activities should avoid complex and high-risk activities, particularly those such as driving that require alertness and coordination, until they have experience using the combination. Consider therapy modification

Phenytoin: May enhance the CNS depressant effect of PHENobarbital. PHENobarbital may decrease the serum concentration of Phenytoin. Phenytoin may increase the serum concentration of PHENobarbital. Monitor therapy

Pimavanserin: CYP3A4 Inducers (Strong) may decrease the serum concentration of Pimavanserin. Monitor therapy

Piribedil: CNS Depressants may enhance the CNS depressant effect of Piribedil. Monitor therapy

PONATinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of PONATinib. Avoid combination

Potassium Chloride: Anticholinergic Agents may enhance the ulcerogenic effect of Potassium Chloride. Management: Patients on drugs with substantial anticholinergic effects should avoid using any solid oral dosage form of potassium chloride. Avoid combination

Potassium Citrate: Anticholinergic Agents may enhance the ulcerogenic effect of Potassium Citrate. Avoid combination

Pramipexole: CNS Depressants may enhance the sedative effect of Pramipexole. Monitor therapy

Pramlintide: May enhance the anticholinergic effect of Anticholinergic Agents. These effects are specific to the GI tract. Consider therapy modification

Praziquantel: CYP3A4 Inducers (Strong) may decrease the serum concentration of Praziquantel. Management: Avoid concomitant use of praziquantel with strong CYP3A4 inducers. Discontinue rifampin 4 weeks prior to initiation of praziquantel therapy. Rifampin may be resumed the day following praziquantel completion. Avoid combination

PrednisoLONE (Systemic): CYP3A4 Inducers (Strong) may decrease the serum concentration of PrednisoLONE (Systemic). Monitor therapy

PredniSONE: CYP3A4 Inducers (Strong) may decrease the serum concentration of PredniSONE. Monitor therapy

Prilocaine: Methemoglobinemia Associated Agents may enhance the adverse/toxic effect of Prilocaine. Combinations of these agents may increase the likelihood of significant methemoglobinemia. Management: Monitor patients for signs of methemoglobinemia (e.g., hypoxia, cyanosis) when prilocaine is used in combination with other agents associated with development of methemoglobinemia. Avoid lidocaine/prilocaine in infants receiving such agents. Monitor therapy

Primidone: May enhance the adverse/toxic effect of Barbiturates. Primidone is converted to phenobarbital, and thus becomes additive with existing barbiturate therapy. Monitor therapy

Propacetamol: Barbiturates may increase the metabolism of Propacetamol. This may 1) diminish the desired effects of propacetamol; and 2) increase the risk of liver damage. Monitor therapy

Propafenone: CYP3A4 Inducers (Strong) may decrease the serum concentration of Propafenone. Monitor therapy

Pyridoxine: May increase the metabolism of Barbiturates. Apparent in high pyridoxine doses (eg, 200 mg/day) Monitor therapy

QUEtiapine: CYP3A4 Inducers (Strong) may decrease the serum concentration of QUEtiapine. Management: An increase in quetiapine dose (as much as 5 times the regular dose) may be required to maintain therapeutic benefit. Reduce the quetiapine dose back to the previous/regular dose within 7-14 days of discontinuing the inducer. Consider therapy modification

QuiNIDine: PHENobarbital may enhance the hepatotoxic effect of QuiNIDine. PHENobarbital may decrease the serum concentration of QuiNIDine. Monitor therapy

QuiNINE: May increase the serum concentration of PHENobarbital. PHENobarbital may decrease the serum concentration of QuiNINE. Consider therapy modification

Radotinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Radotinib. Management: Consider alternatives to this combination when possible as the risk of radotinib treatment failure may be increased. Consider therapy modification

Ramelteon: CYP3A4 Inducers (Strong) may decrease the serum concentration of Ramelteon. Monitor therapy

Ramosetron: Anticholinergic Agents may enhance the constipating effect of Ramosetron. Monitor therapy

Ranolazine: CYP3A4 Inducers (Strong) may decrease the serum concentration of Ranolazine. Avoid combination

Reboxetine: CYP3A4 Inducers (Strong) may decrease the serum concentration of Reboxetine. Monitor therapy

Regorafenib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Regorafenib. Avoid combination

Ribociclib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Ribociclib. Avoid combination

Rifamycin Derivatives: May increase the metabolism of Barbiturates. Monitor therapy

Rilpivirine: PHENobarbital may decrease the serum concentration of Rilpivirine. Avoid combination

RimabotulinumtoxinB: Anticholinergic Agents may enhance the anticholinergic effect of RimabotulinumtoxinB. Monitor therapy

Rivaroxaban: CYP3A4 Inducers (Strong) may decrease the serum concentration of Rivaroxaban. Avoid combination

Roflumilast: CYP3A4 Inducers (Strong) may decrease the serum concentration of Roflumilast. Management: Roflumilast U.S. prescribing information recommends against combining strong CYP3A4 inducers with roflumilast. The Canadian product monograph makes no such recommendation but notes that such agents may reduce roflumilast therapeutic effects. Avoid combination

Rolapitant: CYP3A4 Inducers (Strong) may decrease the serum concentration of Rolapitant. Management: Avoid rolapitant use in patients requiring chronic administration of strong CYP3A4 inducers. Monitor for reduced rolapitant response and the need for alternative or additional antiemetic therapy even with shorter-term use of such inducers. Consider therapy modification

RomiDEPsin: CYP3A4 Inducers (Strong) may decrease the serum concentration of RomiDEPsin. Avoid combination

ROPINIRole: CNS Depressants may enhance the sedative effect of ROPINIRole. Monitor therapy

Rotigotine: CNS Depressants may enhance the sedative effect of Rotigotine. Monitor therapy

Rufinamide: May increase the serum concentration of PHENobarbital. PHENobarbital may decrease the serum concentration of Rufinamide. Monitor therapy

SAXagliptin: CYP3A4 Inducers (Strong) may decrease the serum concentration of SAXagliptin. Monitor therapy

Secretin: Anticholinergic Agents may diminish the therapeutic effect of Secretin. Management: Avoid concomitant use of anticholinergic agents and secretin. Discontinue anticholinergic agents at least 5 half-lives prior to administration of secretin. Consider therapy modification

Selective Serotonin Reuptake Inhibitors: CNS Depressants may enhance the adverse/toxic effect of Selective Serotonin Reuptake Inhibitors. Specifically, the risk of psychomotor impairment may be enhanced. Monitor therapy

Selexipag: CYP2C8 Inducers (Strong) may decrease serum concentrations of the active metabolite(s) of Selexipag. Monitor therapy

Sertraline: CYP3A4 Inducers (Strong) may decrease the serum concentration of Sertraline. Monitor therapy

Simeprevir: CYP3A4 Inducers (Strong) may decrease the serum concentration of Simeprevir. Avoid combination

Sirolimus: CYP3A4 Inducers (Strong) may decrease the serum concentration of Sirolimus. Management: Avoid concomitant use of strong CYP3A4 inducers and sirolimus if possible. If combined, monitor for reduced serum sirolimus concentrations. Sirolimus dose increases will likely be necessary to prevent subtherapeutic sirolimus levels. Consider therapy modification

Sodium Nitrite: Methemoglobinemia Associated Agents may enhance the adverse/toxic effect of Sodium Nitrite. Combinations of these agents may increase the likelihood of significant methemoglobinemia. Monitor therapy

Sodium Oxybate: May enhance the CNS depressant effect of CNS Depressants. Management: Consider alternatives to combined use. When combined use is needed, consider minimizing doses of one or more drugs. Use of sodium oxybate with alcohol or sedative hypnotics is contraindicated. Consider therapy modification

Sofosbuvir: PHENobarbital may decrease the serum concentration of Sofosbuvir. Avoid combination

Somatostatin Acetate: May enhance the adverse/toxic effect of Barbiturates. Specifically, Somatostatin Acetate may enhance or prolong Barbiturate effects, including sedative effects. Avoid combination

Sonidegib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Sonidegib. Avoid combination

SORAfenib: CYP3A4 Inducers (Strong) may decrease the serum concentration of SORAfenib. Avoid combination

Stiripentol: PHENobarbital may decrease the serum concentration of Stiripentol. Avoid combination

Sulthiame: May enhance the adverse/toxic effect of PHENobarbital. Monitor therapy

SUNItinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of SUNItinib. Management: Avoid when possible. If such a combination cannot be avoided, consider increasing sunitinib dose and monitor clinical response and toxicity closely. Consider therapy modification

Suvorexant: CYP3A4 Inducers (Strong) may decrease the serum concentration of Suvorexant. Avoid combination

Tadalafil: CYP3A4 Inducers (Strong) may decrease the serum concentration of Tadalafil. Management: Erectile dysfunction: monitor for decreased effectiveness - no standard dose adjustments recommended. Avoid use of tadalafil for pulmonary arterial hypertension in patients receiving a strong CYP3A4 inducer. Consider therapy modification

Tapentadol: May enhance the CNS depressant effect of CNS Depressants. Management: Avoid concomitant use of tapentadol and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug. Consider therapy modification

Tasimelteon: CYP3A4 Inducers (Strong) may decrease the serum concentration of Tasimelteon. Avoid combination

Telaprevir: PHENobarbital may decrease the serum concentration of Telaprevir. Avoid combination

Temsirolimus: CYP3A4 Inducers (Strong) may decrease the serum concentration of Temsirolimus. Management: Consider increasing the dose of temsirolimus to 50 mg IV/week (from 25 mg IV/week) if a concomitant CYP3A4 strong inducer is necessary. Consider therapy modification

Teniposide: Barbiturates may decrease the serum concentration of Teniposide. Management: Consider alternatives to combined treatment with barbiturates and teniposide due to the potential for decreased teniposide concentrations. If the combination cannot be avoided, monitor teniposide response closely. Consider therapy modification

Tenofovir Alafenamide: PHENobarbital may decrease the serum concentration of Tenofovir Alafenamide. Avoid combination

Tetracaine (Topical): May enhance the adverse/toxic effect of Methemoglobinemia Associated Agents. Monitor therapy

Tetrahydrocannabinol: CYP3A4 Inducers (Strong) may decrease the serum concentration of Tetrahydrocannabinol. Monitor therapy

Tetrahydrocannabinol: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Thalidomide: CNS Depressants may enhance the CNS depressant effect of Thalidomide. Avoid combination

Theophylline Derivatives: Barbiturates may decrease the serum concentration of Theophylline Derivatives. Exceptions: Dyphylline. Monitor therapy

Thiazide and Thiazide-Like Diuretics: Barbiturates may enhance the orthostatic hypotensive effect of Thiazide and Thiazide-Like Diuretics. Monitor therapy

Thiazide and Thiazide-Like Diuretics: Anticholinergic Agents may increase the serum concentration of Thiazide and Thiazide-Like Diuretics. Monitor therapy

Thiothixene: PHENobarbital may decrease the serum concentration of Thiothixene. Monitor therapy

TiaGABine: CYP3A4 Inducers (Strong) may decrease the serum concentration of TiaGABine. Management: Approximately 2-fold higher tiagabine doses and a more rapid dose titration will likely be required in patients concomitantly taking a strong CYP3A4 inducer. Consider therapy modification

Ticagrelor: CYP3A4 Inducers (Strong) may decrease serum concentrations of the active metabolite(s) of Ticagrelor. CYP3A4 Inducers (Strong) may decrease the serum concentration of Ticagrelor. Avoid combination

Tiotropium: Anticholinergic Agents may enhance the anticholinergic effect of Tiotropium. Avoid combination

Tipranavir: PHENobarbital may decrease the serum concentration of Tipranavir. Tipranavir may decrease the serum concentration of PHENobarbital. Consider therapy modification

Tofacitinib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Tofacitinib. Avoid combination

Tolvaptan: CYP3A4 Inducers (Strong) may decrease the serum concentration of Tolvaptan. Management: If concurrent use is necessary, increased doses of tolvaptan (with close monitoring for toxicity and clinical response) may be needed. Avoid combination

Topiramate: Anticholinergic Agents may enhance the adverse/toxic effect of Topiramate. Monitor therapy

Toremifene: CYP3A4 Inducers (Strong) may decrease the serum concentration of Toremifene. Avoid combination

Trabectedin: CYP3A4 Inducers (Strong) may decrease the serum concentration of Trabectedin. Avoid combination

Treprostinil: CYP2C8 Inducers (Strong) may decrease the serum concentration of Treprostinil. Monitor therapy

Tricyclic Antidepressants: Barbiturates may increase the metabolism of Tricyclic Antidepressants. Consider therapy modification

Trimeprazine: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Tropisetron: CYP3A4 Inducers (Strong) may decrease the serum concentration of Tropisetron. Monitor therapy

Udenafil: CYP3A4 Inducers (Strong) may decrease the serum concentration of Udenafil. Monitor therapy

Ulipristal: CYP3A4 Inducers (Strong) may decrease the serum concentration of Ulipristal. Avoid combination

Ulipristal: Barbiturates may decrease the serum concentration of Ulipristal. Avoid combination

Umeclidinium: May enhance the anticholinergic effect of Anticholinergic Agents. Avoid combination

Valbenazine: CYP3A4 Inducers (Strong) may decrease the serum concentration of Valbenazine. Avoid combination

Valproate Products: May increase the serum concentration of Barbiturates. Barbiturates may decrease the serum concentration of Valproate Products. Monitor therapy

Vandetanib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Vandetanib. Avoid combination

Velpatasvir: CYP2C8 Inducers (Strong) may decrease the serum concentration of Velpatasvir. Avoid combination

Velpatasvir: CYP3A4 Inducers (Strong) may decrease the serum concentration of Velpatasvir. Avoid combination

Vemurafenib: CYP3A4 Inducers (Strong) may decrease the serum concentration of Vemurafenib. Management: Avoid concurrent use of vemurafenib with a strong CYP3A4 inducer and replace with another agent when possible. If a strong CYP3A4 inducer is indicated and unavoidable, the dose of vemurafenib may be increased by 240 mg (1 tablet) as tolerated. Consider therapy modification

Venetoclax: CYP3A4 Inducers (Strong) may decrease the serum concentration of Venetoclax. Avoid combination

Vilazodone: CYP3A4 Inducers (Strong) may decrease the serum concentration of Vilazodone. Management: Consider increasing vilazodone dose by as much as 2-fold (do not exceed 80 mg/day), based on response, in patients receiving strong CYP3A4 inducers for > 14 days. Reduce to the original vilazodone dose over 1-2 weeks after inducer discontinuation. Consider therapy modification

VinCRIStine (Liposomal): CYP3A4 Inducers (Strong) may decrease the serum concentration of VinCRIStine (Liposomal). Avoid combination

Vinflunine: CYP3A4 Inducers (Strong) may decrease the serum concentration of Vinflunine. Avoid combination

Vitamin K Antagonists (eg, warfarin): Barbiturates may increase the metabolism of Vitamin K Antagonists. Management: Monitor INR more closely. An anticoagulant dose increase may be needed after a barbiturate is initiated or given at an increased dose. Anticoagulant dose decreases may be needed following barbiturate discontinuation or dose reduction. Consider therapy modification

Vorapaxar: CYP3A4 Inducers (Strong) may decrease the serum concentration of Vorapaxar. Avoid combination

Voriconazole: Barbiturates may decrease the serum concentration of Voriconazole. Avoid combination

Vortioxetine: CYP3A4 Inducers (Strong) may decrease the serum concentration of Vortioxetine. Management: Consider increasing the vortioxetine dose to no more than 3 times the original dose when used with a strong drug metabolism inducer for more than 14 days. The vortioxetine dose should be returned to normal within 14 days of stopping the strong inducer. Consider therapy modification

Voxilaprevir: CYP3A4 Inducers (Strong) may decrease the serum concentration of Voxilaprevir. Avoid combination

Zaleplon: CYP3A4 Inducers (Strong) may decrease the serum concentration of Zaleplon. Management: Consider the use of an alternative hypnotic that is not metabolized by CYP3A4 in patients receiving strong CYP3A4 inducers. If zalephon is combined with a strong CYP3A4 inducer, monitor for decreased effectiveness of zaleplon. Consider therapy modification

Zolpidem: CNS Depressants may enhance the CNS depressant effect of Zolpidem. Management: Reduce the Intermezzo brand sublingual zolpidem adult dose to 1.75 mg for men who are also receiving other CNS depressants. No such dose change is recommended for women. Avoid use with other CNS depressants at bedtime; avoid use with alcohol. Consider therapy modification

Zonisamide: PHENobarbital may decrease the serum concentration of Zonisamide. Monitor therapy

Zuclopenthixol: CYP3A4 Inducers (Strong) may decrease the serum concentration of Zuclopenthixol. Monitor therapy

Reproduction studies with this combination have not been done; refer to individual monographs.

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience, fatigue, anxiety, dry mouth, or change in taste. Have patient report immediately to prescriber signs of depression (suicidal ideation, anxiety, emotional instability, or illogical thinking), difficulty breathing, severe loss of strength and energy, severe dizziness, passing out, change in balance, confusion, hallucinations, memory impairment, insomnia, severe constipation, diarrhea, lack of sweat, muscle pain, muscle cramps, tachycardia, arrhythmia, urinary retention, vision changes, severe headache, severe nausea, severe vomiting, or signs of Stevens-Johnson syndrome/toxic epidermal necrolysis (red, swollen, blistered, or peeling skin [with or without fever]; red or irritated eyes; or sores in mouth, throat, nose, or eyes) (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment, in diagnosing, treating and advising patients.