Abstral Sublingual Tablet

ABSTRAL is contraindicated in:

• Opioid non-tolerant patients. Life-threatening respiratory depression and death could occur at any dose in opioid non-tolerant patients [see Indications and Usage (1), Warnings and Precautions (5.1)].
• Acute or postoperative pain, including headache/migraine, dental pain, or use in the emergency department.
• Acute or severe bronchial asthma in an unmonitored setting or in the absence of resuscitative equipment [see Warnings and Precautions (5.9)].
• Known or suspected gastrointestinal obstruction, including paralytic ileus [see Warnings and Precautions (5.14)].
• Known hypersensitivity to fentanyl (e.g., anaphylaxis) [see Adverse Reactions (6.2)].

The following serious adverse reactions are described, or described in greater detail, in other sections:

• Life-Threatening Respiratory Depression [see Warnings and Precautions (5.1)]
• Interactions with Benzodiazepines and Other CNS Depressants [see Warnings and Precautions (5.4)]
• Addiction, Abuse, and Misuse [see Warnings and Precautions (5.6)]
• Neonatal Opioid Withdrawal Syndrome [see Warnings and Precautions (5.8)]
• Serotonin Syndrome [see Warnings and Precautions (5.10)]
• Adrenal Insufficiency [see Warnings and Precautions (5.11)]
• Severe Hypotension [see Warnings and Precautions (5.12)]
• Gastrointestinal Adverse Reactions [see Warnings and Precautions (5.14)]
• Seizures [see Warnings and Precautions (5.15)]

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The safety of ABSTRAL has been evaluated in 311 opioid-tolerant cancer patients with breakthrough pain. Two hundred and seventy (270) of these patients were treated in multiple-dose studies. The duration of therapy for patients in multiple-dose studies ranged from 1-405 days with an average duration of 131 days and with 44 patients treated for at least 12 months.

The clinical trials of ABSTRAL were designed to evaluate safety and efficacy in treating patients with cancer and breakthrough pain. All patients were taking concomitant opioids, such as sustained-release morphine, sustained-release oxycodone, or transdermal fentanyl, for their persistent pain.

The adverse reaction data presented in Table 2 reflect the actual percentage of patients experiencing reactions among patients who received ABSTRAL for breakthrough pain along with concomitant opioid use for persistent pain. There has been no attempt to correct for concomitant use of other opioids, duration of ABSTRAL therapy, or cancer-related symptoms.

Table 2 lists adverse reactions with an overall frequency of 5% or greater within the total population that occurred during titration by maximum dose received. The ability to assign ABSTRAL a dose-response relationship to these adverse reactions is limited by the titration schemes used in these studies.

Table 3 lists, by successful dose, adverse reactions with an overall frequency of ≥ 5% within the total population that occurred after a successful dose had been determined.

The frequencies listed below represent adverse reactions that occurred in ≥1% of patients from two clinical trials who experienced that reaction while receiving ABSTRAL. Reactions are classified by system organ class.

Adverse Reactions (≥ 1%)

Cardiac disorders: bradycardia, tachycardia.

Eye disorders: vision blurred.

Gastrointestinal disorders: abdominal pain, abdominal pain upper, aphthous stomatitis, constipation, dry mouth, dyspepsia, gingival ulceration, impaired gastric emptying, lip ulceration, mouth ulceration, nausea, stomach discomfort, stomatitis, tongue disorder, vomiting.

General disorders and administration site conditions: asthenia, drug withdrawal syndrome, fatigue, malaise.

Immune system disorders: drug hypersensitivity.

Injury, poisoning and procedural complications: accidental overdose.

Metabolism and nutrition disorders: anorexia, decreased appetite.

Nervous system disorders: amnesia, disturbance in attention, dizziness, dysgeusia, headache, hypoesthesia, lethargy, parosmia, somnolence, tremor.

Psychiatric disorders: affect lability, anxiety, confusional state, depression, disorientation, dysphoria, euphoric mood, insomnia, mental status changes, paranoia, sleep disorder.

Reproductive system and breast disorders: erectile dysfunction.

Respiratory, thoracic and mediastinal disorder: dyspnea, oropharyngeal pain, throat tightness.

Skin and subcutaneous disorders: hyperhidrosis, night sweats, pruritus, rash, skin lesion.

Vascular disorders: hypotension.

Postmarketing Experience

The following adverse reactions have been identified during post approval use of fentanyl. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Serotonin Syndrome: Cases of serotonin syndrome, a potentially life-threatening condition, have been reported during concomitant use of opioids with serotonergic drugs.

Adrenal Insufficiency: Cases of adrenal insufficiency have been reported with opioid use, more often following greater than one month of use.

Anaphylaxis: Anaphylaxis has been reported with ingredients contained in ABSTRAL.

Androgen Deficiency: Cases of androgen deficiency have occurred with chronic use of opioids.

Mechanism of Action

Fentanyl is an opioid agonist whose principal therapeutic action is analgesia.

Pharmacodynamics

Effects on the Central Nervous System

Fentanyl produces respiratory depression by direct action on brain stem respiratory centers. The respiratory depression involves both a reduction in the responsiveness of the brain stem respiratory centers to increases in carbon dioxide tension and to electrical stimulation.

Fentanyl causes miosis, even in total darkness. Pinpoint pupils are a sign of opioid overdose but are not pathognomonic (e.g., pontine lesions of hemorrhagic or ischemic origins may produce similar findings). Marked mydriasis rather than miosis may be seen due to hypoxia in overdose situations.

Effects on the Gastrointestinal Tract and Other Smooth Muscle

Fentanyl causes a reduction in motility associated with an increase in smooth muscle tone in the antrum of the stomach and in the duodenum. Digestion of food is delayed in the small intestine and propulsive contractions are decreased. Propulsive peristaltic waves in the colon are decreased, while tone may be increased to the point of spasm resulting in constipation. Other opioid induced-effects may include a reduction in gastric, biliary and pancreatic secretions, spasm of the sphincter of Oddi, and transient elevations in serum amylase.

Effects on the Cardiovascular System

Fentanyl produces peripheral vasodilation which may result in orthostatic hypotension or syncope. Manifestations of histamine release and/or peripheral vasodilation may include pruritus, flushing, red eyes and sweating, and/or orthostatic hypotension.

Effects on the Endocrine System

Opioids inhibit the secretion of adrenocorticotropic hormone (ACTH), cortisol, and luteinizing hormone (LH) in humans [see Adverse Reactions (6.2)]. They also stimulate prolactin, growth hormone (GH) secretion, and pancreatic secretion of insulin and glucagon.

Chronic use of opioids may influence the hypothalamic-pituitary-gonadal axis, leading to androgen deficiency that may manifest as low libido, impotence, erectile dysfunction, amenorrhea, or infertility. The causal role of opioids in the clinical syndrome of hypogonadism is unknown because the various medical, physical, lifestyle, and psychological stressors that may influence gonadal hormone levels have not been adequately controlled for in studies conducted to date [see Adverse Reactions (6.2)].

Effects on the Immune System

Opioids have been shown to have a variety of effects on components of the immune system in in vitro and animal models. The clinical significance of these findings is unknown. Overall, the effects of opioids appear to be modestly immunosuppressive.

Concentration–Efficacy Relationships

The analgesic effects of fentanyl are related to the blood level of the drug, if proper allowance is made for the delay into and out of the CNS (a process with a 3- to 5-minute half-life).

In general, the effective concentration and the concentration at which toxicity occurs increase with increasing tolerance with any and all opioids. The rate of development of tolerance varies widely among individuals [see Dosage and Administration (2.3)].

The minimum effective analgesic concentration of fentanyl for any individual patient may increase over time due to an increase in pain, the development of a new pain syndrome, and/or the development of analgesic tolerance [see Dosage and Administration (2.2, 2.3)].

Concentration–Adverse Reaction Relationships

There is a relationship between increasing fentanyl plasma concentration and increasing frequency of dose-related opioid adverse reactions such as nausea, vomiting, CNS effects, and respiratory depression. In opioid-tolerant patients, the situation may be altered by the development of tolerance to opioid-related adverse reactions [see Dosage and Administration (2.2, 2.3)].

Respiratory System

All opioid mu-receptor agonists, including fentanyl, produce dose-dependent respiratory depression. The risk of respiratory depression is less in patients receiving chronic opioid therapy who develop tolerance to respiratory depression and other opioid effects. Peak respiratory depressive effects may be seen as early as 15 to 30 minutes from the start of oral transmucosal fentanyl citrate administration and may persist for several hours.

Serious or fatal respiratory depression can occur even at recommended doses. Although not observed with oral transmucosal fentanyl products in clinical trials, fentanyl given rapidly by intravenous injection in large doses may cause rigidity in the muscles of respiration resulting in respiratory difficulties [see Warnings and Precautions (5.1)].

Pharmacokinetics

Absorption

Fentanyl is a highly lipophilic drug. Orally administered fentanyl undergoes pronounced hepatic and intestinal first pass effects. Absorption of fentanyl from Abstral Sublingual Tablets is mainly through the oral mucosa.

The bioavailability of Abstral Sublingual Tablets has been calculated to be 54%.

Dose proportionality across the 100 mcg to 800 mcg ABSTRAL dose range has been demonstrated (Table 4). Mean plasma fentanyl levels following single doses of ABSTRAL are shown in Figure 1. The median time to maximum plasma concentration (Tmax) across these four doses of ABSTRAL varied from 30 to 60 minutes (range of 15 - 240 minutes).

Figure 1: Mean (+/- SD) Plasma Fentanyl Concentration versus Time after Administration of Single Doses of 100 mcg, 200 mcg, 400 mcg and 800 mcg ABSTRAL to Healthy Subjects

Pharmacokinetic parameters are presented in Table 5.

In another study, dose proportionality between 800 mcg and 1600 mcg in Cmax and AUC has also been demonstrated.

Pharmacokinetic studies have shown that multiple tablets are bioequivalent to single tablets of the equivalent dose.

Distribution

Fentanyl is highly lipophilic. Animal data showed that following absorption, fentanyl is rapidly distributed to the brain, heart, lungs, kidneys and spleen followed by a slower redistribution to muscles and fat. The plasma protein binding of fentanyl is 80-85%. The main binding protein is alpha-1-acid glycoprotein, but both albumin and lipoproteins contribute to some extent. The free fraction of fentanyl increases with acidosis. The mean volume of distribution at steady state (Vss) was 4 L/kg.

Elimination

Metabolism

Fentanyl is metabolized in the liver and in the intestinal mucosa to norfentanyl by cytochrome P450 3A4 isoform. Norfentanyl was not found to be pharmacologically active in animal studies [see Drug Interactions (7)].

Excretion

Fentanyl is more than 90% eliminated by biotransformation to N-dealkylated and hydroxylated inactive metabolites. Less than 7% of the dose is excreted unchanged in the urine, and only about 1% is excreted unchanged in the feces. The metabolites are mainly excreted in the urine, while fecal excretion is less important. The total plasma clearance of fentanyl was 0.5 L/hr/kg (range 0.3 - 0.7 L/hr/kg).

The efficacy of ABSTRAL was investigated in a clinical trial in opioid tolerant adult patients experiencing breakthrough cancer pain. Breakthrough cancer pain was defined as a transient flare of moderate-to-severe pain occurring in patients with cancer who experience persistent cancer pain otherwise controlled with maintenance doses of opioid medications, including at least 60 mg morphine/day, 50 mcg transdermal fentanyl/hour, or an equianalgesic dose of another opioid for 1 week or longer. All patients were on stable doses of either long-acting oral opioids or transdermal fentanyl for their persistent cancer pain.

A double-blind, placebo-controlled, crossover study was performed in patients with cancer to evaluate the effectiveness of ABSTRAL for the treatment of breakthrough cancer pain. Open-label titration identified a dose of ABSTRAL in which a patient obtained adequate analgesia with tolerable side effects, within the range of 100 mcg to 800 mcg. In the double-blind efficacy study, patients who identified a successful dose were randomized to a sequence of 10 treatments; seven with ABSTRAL and three with placebo.

Of the 131 patients who entered the titration phase of the study, 78 (60%) achieved a successful dose during the titration phase. Sixty-six patients entered the double-blind phase and 60 completed the study. The dose of ABSTRAL was determined by titration starting at 100 mcg. The final titrated dose of ABSTRAL for breakthrough cancer pain was not predicted from the daily maintenance dose of opioid used to manage the persistent cancer pain. In a second open-label safety study using an identical titration regimen, 96 of 139 patients (69%) who entered the study titrated to a dose in which the patient obtained adequate analgesia with tolerable side effects during the titration phase. Table 6 presents the final titrated dose for both the double-blind efficacy and open-label safety studies.

The primary outcome measure, the mean sum of pain intensity difference at 30 minutes (SPID30) for ABSTRAL-treated episodes, was statistically significantly higher than for placebo-treated episodes.

Figure 2: Mean Pain Intensity Difference (±SE) for ABSTRAL Compared to Placebo