Darvon

CIV

Rx only

• There have been numerous cases of accidental and intentional overdose with propoxyphene products either alone or in combination with other CNS depressants, including alcohol. Fatalities within the first hour of overdosage are not uncommon. Many of the propoxyphene-related deaths have occurred in patients with previous histories of emotional disturbances or suicidal ideation/attempts and/or concomitant administration of sedatives, tranquilizers, muscle relaxants, antidepressants, or other CNS-depressant drugs. Do not prescribe propoxyphene for patients who are suicidal or have a history of suicidal ideation.
• The metabolism of propoxyphene may be altered by strong CYP3A4 inhibitors (such as ritonavir, ketoconazole, itraconazole, troleandomycin, clarithromycin, nelfinavir, nefazadone, amiodarone, amprenavir, aprepitant, diltiazem, erythromycin, fluconazole, fosamprenavir, grapefruit juice, and verapamil) leading to enhanced propoxyphene plasma levels. Patients receiving propoxyphene and any CYP3A4 inhibitor should be carefully monitored for an extended period of time and dosage adjustments should be made if warranted (see CLINICAL PHARMACOLOGY – Drug Interactions and WARNINGS, PRECAUTIONS and DOSAGE AND ADMINISTRATION for further information).

Darvon contains propoxyphene hydrochloride, USP which is an odorless, white crystalline powder with a bitter taste. It is freely soluble in water. Chemically, it is (2S,3R)-(+)-4-(Dimethylamino)-3-methyl-1,2-diphenyl-2-butanol propionate (ester) hydrochloride, which can be represented by the accompanying structural formula. Its molecular weight is 375.94.

Each pulvule contains 65 mg (172.9 μmol) propoxyphene hydrochloride. It also contains D & C Red No. 33, F D & C Yellow No. 6, gelatin, magnesium stearate, silicone, starch, titanium dioxide, and other inactive ingredients.

Controlled Substance

Darvon is a Schedule IV narcotic under the U.S. Controlled Substances Act. Darvon can produce drug dependence of the morphine type, and therefore, has the potential for being abused. Psychic dependence, physical dependence and tolerance may develop upon repeated administration. Darvon should be prescribed and administered with the same degree of caution appropriate to the use of other narcotic-containing medications.

Abuse

Since Darvon is a mu-opioid agonist, it may be subject to misuse, abuse, and addiction. Addiction to opioids prescribed for pain management has not been estimated. However, requests for opioids from opioid-addicted patients occur. As such, physicians should take appropriate care in prescribing Darvon.

Dependence

Opioid analgesics may cause psychological and physical dependence. Physical dependence results in withdrawal symptoms in patients who abruptly discontinue the drug after long term administration. Also, symptoms of withdrawal may be precipitated through the administration of drugs with mu-opioid antagonist activity, e.g., naloxone or mixed agonist/antagonist analgesics (pentazocine, butorphanol, nalbuphine, dezocine) (see OVERDOSAGE). Physical dependence usually does not occur to a clinically significant degree, until after several weeks of continued opioid usage. Tolerance, in which increasingly larger doses are required to produce the same degree of analgesia, is initially manifested by a shortened duration of an analgesic effect and subsequently, by decreases in the intensity of analgesia.

In chronic pain patients, and in opioid-tolerant cancer patients, the administration of Darvon should be guided by the degree of tolerance manifested and the doses needed to adequately relieve pain.

The severity of the Darvon abstinence syndrome may depend on the degree of physical dependence. Withdrawal is characterized by rhinitis, myalgia, abdominal cramping, and occasional diarrhea. Most observable symptoms disappear in 5 to 14 days without treatment; however, there may be a phase of secondary or chronic abstinence which may last for 2 to 6 months characterized by insomnia, irritability, and muscular aches. The patient may be detoxified by gradual reduction of the dose. Gastrointestinal disturbances or dehydration should be treated with supportive care.

Overdose of Darvon may present with the signs and symptoms of propoxyphene overdose. Fatalities within the first hour of overdosage are not uncommon.

In all cases of suspected overdosage, call your regional Poison Control Center to obtain the most up-to-date information about the treatment of overdose. This recommendation is made because, in general, information regarding the treatment of overdosage may change more rapidly than do package inserts.

Initial consideration should be given to the management of the CNS effects of propoxyphene overdosage. Resuscitative measures should be initiated promptly.

Symptoms of Propoxyphene Overdosage

The manifestations of acute overdosage with propoxyphene are those of narcotic overdosage. The patient is usually somnolent but may be stuporous or comatose and convulsing. Respiratory depression is characteristic. The ventilatory rate and/or tidal volume is decreased, which results in cyanosis and hypoxia. Pupils, initially pinpoint, may become dilated as hypoxia increases. Cheyne-Stokes respiration and apnea may occur. Blood pressure and heart rate are usually normal initially, but blood pressure falls and cardiac performance deteriorates, which ultimately results in pulmonary edema and circulatory collapse, unless the respiratory depression is corrected and adequate ventilation is restored promptly. Cardiac arrhythmias and conduction delay may be present. A combined respiratory-metabolic acidosis occurs owing to retained CO2 (hypercapnia) and to lactic acid formed during anaerobic glycolysis. Acidosis may be severe if large amounts of salicylates have also been ingested. Death may occur.

Treatment of Propoxyphene Overdosage

Attention should be directed first to establishing a patent airway and to restoring ventilation. Mechanically assisted ventilation, with or without oxygen, may be required, and positive pressure respiration may be desirable if pulmonary edema is present. The opioid antagonist naloxone will markedly reduce the degree of respiratory depression, and should be administered promptly, preferably intravenously. The duration of action of the antagonist may be brief. If no response is observed after 10 mg of naloxone have been administered, the diagnosis of propoxyphene toxicity should be questioned.

In addition to the use of an opioid antagonist, the patient may require careful titration with an anticonvulsant to control convulsions. Activated charcoal can adsorb a significant amount of ingested propoxyphene. Dialysis is of little value in poisoning due to propoxyphene. Efforts should be made to determine whether other agents, such as alcohol, barbiturates, tranquilizers, or other CNS depressants, were also ingested, since these increase CNS depression as well as cause specific toxic effects or death.

Darvon is intended for the management of mild to moderate pain. The dose should be individually adjusted according to severity of pain, patient response and patient size.

Darvon is given orally. The usual dosage is one 65 mg propoxyphene hydrochloride capsule every 4 hours as needed for pain. The maximum dose of Darvon is 6 tablets per day. Do not exceed the maximum daily dose.

Patients receiving propoxyphene and any CYP3A4 inhibitor should be carefully monitored for an extended period of time and dosage adjustments should be made if warranted.

Consideration should be given to a reduced total daily dosage in elderly patients and in patients with hepatic or renal impairment.

Cessation of Therapy

For patients who used Darvon on a regular basis for a period of time, when therapy with Darvon is no longer needed for the treatment of their pain, it may be useful to gradually discontinue the Darvon over time to prevent the development of an opioid abstinence syndrome (narcotic withdrawal). In general, therapy can be decreased by 25% to 50% per day with careful monitoring for signs and symptoms of withdrawal (see DRUG ABUSE AND DEPENDENCE for description of the signs and symptoms of withdrawal). If the patient develops these signs or symptoms, the dose should be raised to the previous level and titrated down more slowly, either by increasing the interval between decreases, decreasing the amount of change in dose, or both.

In most cases of congenital malformations in infants exposed to propoxyphene, other drugs were also used during pregnancy and a clear association between propoxyphene use and the malformations has not been established. Some of the specific malformations described in case reports of infants exposed to propoxyphene (and often other drugs) have included: prune perineum, Pierre Robin syndrome, arthrogryposis, severe caudal dysplasia, micrognathia, microcephaly, ductus arteriosus persistens, cataract, benign tumors, club foot, and limb reduction defects. The Collaborative Perinatal Project identified 686 mother-child pairs with first trimester exposure to propoxyphene and observed 31 malformed children. (In that group, 34.4 malformed children were expected.) A study of Michigan Medicaid patients identified 1029 neonates exposed in utero to propoxyphene and observed 41 malformed children (personal communication, Franz Rosa, MD, Food and Drug Administration, 1994). (In that group, 43 malformed children were expected.) Neonatal propoxyphene withdrawal symptoms include irritability, hypertonicity, jitteriness, increased temperature, tremors, increased appetite, diarrhea and high-pitched cry.

Propoxyphene has not been formally assigned to a pregnancy category by the FDA. Several case reports have described infants exposed to propoxyphene in utero who were born with a variety of congenital malformations. Withdrawal symptoms have also been reported in neonates whose mothers took propoxyphene during pregnancy. There are no controlled data in human pregnancy. Propoxyphene is only recommended for use during pregnancy when benefit outweighs risk.

Summary of Use during Lactation

Maternal use of oral narcotics during breastfeeding can cause infant drowsiness, central nervous system depression and even death. Newborn infants seem to be particularly sensitive to the effects of even small dosages of propoxyphene may be particularly prone to causing these effects. Propoxyphene should be avoided during breastfeeding.[1]

Drug Levels

Propoxyphene is metabolized to active norpropoxyphene (25%) and to several inactive metabolites. Norpropoxyphene has a 30 to 36 hour half-life. The oral bioavailability of norpropoxyphene is unknown. Propoxyphene is available in 2 salt forms: 65 mg of the hydrochloride form is equivalent to 100 mg of the napsylate.

Maternal Levels. Six breastfeeding mothers, 5 in the first few days postcesarean section and 1 at 10 months postpartum were given oral propoxyphene hydrochloride 130 mg once then 65 mg every 4 hours for 16 hours for a cumulative dose of 390 mg. Breastmilk propoxyphene was measured at 1, 3, 5, 7, and 9 hours after the last dose. Propoxyphene peak levels occurred at 3 hours while norpropoxyphene levels remained fairly constant. An average propoxyphene and norpropoxyphene milk level over the 8-hour collection period was calculated for each patient and varied substantially among patients (range 24 to 210 mcg/L for propoxyphene and 54 to 606 mcg/L for norpropoxyphene). Norpropoxyphene had a longer maternal plasma half-life and thus accumulated in breastmilk more so than propoxyphene. Greater breastmilk production was associated with higher milk levels of both propoxyphene and norpropoxyphene.[2][3] Using the highest average milk propoxyphene level in this study, an exclusively breastfed infant would receive 32 mcg/kg daily of propoxyphene and 91 mcg/kg daily of norpropoxyphene, equivalent to about 2% of the maternal weight-adjusted dosage.

Infant Levels. Relevant published information was not found as of the revision date.

Effects in Breastfed Infants

In a case-control study of 12 breastfed term newborns with unexplained episodes of apnea, bradycardia or cyanosis during the first week of life, maternal oral propoxyphene use was determined to be the probable cause. A higher proportion of newborns with episodes, 83 compared to 31%, had mothers using opiates, including propoxyphene, for postpartum analgesia. The mean number of doses taken was also higher with mothers of affected newborns taking a mean of 10 doses (range 4 to 22) compared to 5 doses (range 1 to 13) in the control group.[4]

A fullterm breastfed infant had mild hypotonia and nursing poorly at 10 days of age; the infant had not regained her birth weight by this time. By 7 days later, the mother had less milk and stopped nursing. The infant's mother had been prescribed 6 capsules daily of propoxyphene 30 mg plus acetaminophen 500 mg for the first 10 days postpartum. Hair samples from the infant were positive for propoxyphene and norpropoxyphene and were higher than the mother's hair sample concentrations.[5] Propoxyphene was probably the cause of the adverse reactions in the infant.

All adverse reactions in breastfed infants reported in France between January 1985 and June 2011 were compiled by a French pharmacovigilance center. Of 174 reports, propoxyphene was reported to cause adverse reactions in 11 infants and to be one of the drugs most often suspected in serious adverse reactions. Reactions included hypotonia, apnea, respiratory distress, bradycardia, constipation and weight loss.[6]

Effects on Lactation and Breastmilk

Narcotics can increase serum prolactin.[7] However, the prolactin level in a mother with established lactation may not affect her ability to breastfeed.

Alternate Drugs to Consider

Acetaminophen, Butorphanol, Hydromorphone, Ibuprofen, Morphine

References

1. Sachs HC and the American Academy of Pediatrics committee on Drugs. The transfer of drugs and therapeutics into human breast milk: An update on selected topics. Pediatrics. 2013;132:e796-809. PMID: 23979084

2. Kunka RL, Venkataramanan R, Stern RM et al. Excretion of propoxyphene and norpropoxyphene in breast milk. Clin Pharmacol Ther. 1984;35:675-80. PMID: 6713779

3. Kunka RL, Yong CL, Ladik CF et al. Liquid chromatographic determination of propoxyphene and norpropoxyphene in plasma and breast milk. J Pharm Sci. 1985;74:103-4. PMID: 3981406

4. Naumburg EG, Meny RG. Breast milk opioids and neonatal apnea. Am J Dis Child. 1988;142:11-2. Letter. PMID: 3341293

5. Rigourd V, Amirouche A, Tasseau A et al. Retrospective diagnosis of an adverse drug reaction in a breastfed neonate: liquid chromatography-tandem mass spectrometry quantification of dextropropoxyphene and norpropoxyphene in newborn and maternal hair. J Anal Toxicol. 2008;32:787-9. PMID: 19021937

6. Soussan C, Gouraud A, Portolan G et al. Drug-induced adverse reactions via breastfeeding: a descriptive study in the French Pharmacovigilance Database. Eur J Clin Pharmacol. 2014;70:1361-6. PMID: 25183382

7. Tolis G, Dent R, Guyda H. Opiates, prolactin, and the dopamine receptor. J Clin Endocrinol Metab. 1978;47:200-3. PMID: 263291

Substance Name

Propoxyphene

CAS Registry Number

469-62-5

Drug Class

Analgesics, Opioid

Narcotics

LactMed Record Number

382

Last Revision Date

20141107

Disclaimer

Information presented in this database is not meant as a substitute for professional judgment. You should consult your healthcare provider for breastfeeding advice related to your particular situation. The U.S. government does not warrant or assume any liability or responsibility for the accuracy or completeness of the information on this Site.