5.1 Potential Risk of Myocardial Infarction with Long-Term Use

There were more reports of myocardial infarctions in patients treated with alvimopan 0.5 mg twice daily compared with placebo-treated patients in a 12-month study of patients treated with opioids for chronic non-cancer pain (alvimopan 0.5 mg, n=538; placebo, n=267).

In this study, the majority of myocardial infarctions occurred between 1 and 4 months after initiation of treatment. This imbalance has not been observed in other studies of alvimopan in patients treated with opioids for chronic pain, nor in patients treated within the surgical setting, including patients undergoing surgeries that included bowel resection who received alvimopan 12 mg twice daily for up to 7 days (the indicated dose and patient population; alvimopan 12 mg, n=1,142; placebo, n=1,120). A causal relationship with alvimopan with long-term use has not been established.

Alvimopan capsules are available only through a program under a REMS that restricts use to enrolled hospitals [see Warnings and Precautions (5.2)].

5.2 Alvimopan REMS Program

Alvimopan capsules are available only through a program called the Alvimopan REMS Program that restricts use to enrolled hospitals because of the potential risk of myocardial infarction with long-term use of alvimopan capsules [see Warnings and Precautions (5.1)].

Notable requirements of the Alvimopan REMS Program include the following:

Alvimopan capsules are available only for short-term (15 doses) use in hospitalized patients. Only hospitals that have enrolled in and met all of the requirements for the Alvimopan REMS Program may use alvimopan capsules.

To enroll in the Alvimopan REMS Program, an authorized hospital representative must acknowledge that:

• hospital staff who prescribe, dispense, or administer alvimopan capsules have been provided the educational materials on the need to limit use of alvimopan capsules to short-term, inpatient use;

• patients will not receive more than 15 doses of alvimopan capsules; and

• alvimopan capsules will not be dispensed to patients after they have been discharged from the hospital.

Further information is available at www.alvimopanREMS.com or 1-800-278-0340.

5.3 Gastrointestinal-Related Adverse Reactions in Opioid-Tolerant Patients

Patients recently exposed to opioids are expected to be more sensitive to the effects of mu-opioid receptor antagonists, such as alvimopan. Since alvimopan acts peripherally, clinical signs and symptoms of increased sensitivity would be related to the gastrointestinal tract (e.g., abdominal pain, nausea and vomiting, diarrhea). Patients receiving more than 3 doses of an opioid within the week prior to surgery were not studied in the postoperative ileus clinical trials. Therefore, if alvimopan is administered to these patients, they should be monitored for gastrointestinal adverse reactions. Alvimopan is contraindicated in patients who have taken therapeutic doses of opioids for more than 7 consecutive days immediately prior to taking alvimopan [see Contraindications (4)].

5.4 Risk of Serious Adverse Reactions in Patients with Severe Hepatic Impairment

Patients with severe hepatic impairment may be at higher risk of serious adverse reactions (including dose-related serious adverse reactions) because up to 10-fold higher plasma concentrations of alvimopan have been observed in such patients compared with patients with normal hepatic function. Therefore, the use of alvimopan is not recommended in this population [see Use in Specific Populations (8.6)].

5.5 End-Stage Renal Disease

No studies have been conducted in patients with end-stage renal disease. Alvimopan is not recommended for use in these patients [see Use in Specific Populations (8.7)].

5.6 Risk of Serious Adverse Reactions in Patients with Complete Gastrointestinal Obstruction

No studies have been conducted in patients with complete gastrointestinal obstruction or in patients who have surgery for correction of complete bowel obstruction. Alvimopan is not recommended for use in these patients.

5.7 Risk of Serious Adverse Reactions in Pancreatic and Gastric Anastomoses

Alvimopan has not been studied in patients having pancreatic or gastric anastomosis. Therefore, alvimopan is not recommended for use in these patients.

6.1 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 compared directly with rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. The adverse event information from clinical trials does, however, provide a basis for identifying the adverse events that appear to be related to drug use and for approximating rates.

The data described below reflect exposure to alvimopan 12 mg in 1,793 patients in 10 placebo-controlled studies. The population was 19 to 97 years old, 64% were female, and 84% were Caucasian; 64% were undergoing a surgery that included bowel resection. The first dose of alvimopan was administered 30 minutes to 5 hours before the scheduled start of surgery and then twice daily until hospital discharge (or for a maximum of 7 days of postoperative treatment).

Among alvimopan-treated patients undergoing surgeries that included a bowel resection, the most common adverse reaction (incidence ≥1.5%) occurring with a higher frequency than placebo was dyspepsia (alvimopan, 1.5%; placebo, 0.8%). Adverse reactions are events that occurred after the first dose of study medication treatment and within 7 days of the last dose of study medication or events present at baseline that increased in severity after the start of study medication treatment.

7.1 Effects of Alvimopan on Intravenous Morphine

Coadministration of alvimopan does not appear to alter the pharmacokinetics of morphine and its metabolite, morphine-6-glucuronide, to a clinically significant degree when morphine is administered intravenously. Dosage adjustment for intravenously administered morphine is not necessary when it is coadministered with alvimopan.

7.2 Effects of Concomitant Acid Blockers or Antibiotics

A population pharmacokinetic analysis suggests that the pharmacokinetics of alvimopan were not affected by concomitant administration of acid blockers (proton pump inhibitors (PPIs), histamine-2 (H2) receptor antagonists) or antibiotics. No dosage adjustments are necessary in patients taking acid blockers or antibiotics with alvimopan.

8.1 Pregnancy

Risk Summary

Available data regarding use of alvimopan in pregnant women are limited, and are insufficient to inform a drug-associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes.

No fetal harm was observed in animal reproduction studies with oral administration of alvimopan during organogenesis to pregnant rats at doses 68 to 136 times the recommended human oral dose, or with intravenous administration during organogenesis to pregnant rats and pregnant rabbits at doses 3.4 to 6.8 times, and 5 to 10 times, respectively, the recommended human oral dose (see Data).

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.

Data

Animal Data

Embryo-fetal studies were performed in pregnant rats during organogenesis (gestation days 7 through 19, or 20) at oral doses up to 200 mg/kg/day (about 68 to 136 times the recommended human oral dose based on body surface area) and at intravenous doses up to 10 mg/kg/day (about 3.4 to 6.8 times the recommended human oral dose based on body surface area). A study in pregnant rabbits during organogenesis (gestation days 6 through 18) at intravenous doses up to 15 mg/kg/day (about 5 to 10 times the recommended human oral dose based on body surface area) revealed no evidence of harm to the fetus due to alvimopan.

In an intravenous pre- and postnatal development study (gestation day 7 through lactation day 20) in rats, alvimopan did not cause any adverse effect on pre- and postnatal development at doses up to 10 mg/kg/day (about 6.8 times the recommended human oral dose based on body surface area).

8.2 Lactation

Risk Summary

There are no data on the presence of alvimopan in human milk, the effects on the breastfed infant, or the effects on milk production. Alvimopan and its ‘metabolite’ are detected in the milk of lactating rats following intravenous administration (see Data). It is unknown if alvimopan is present in rat milk following oral administration.

The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for alvimopan and any potential adverse effects on the breastfed child from alvimopan or from the underlying maternal condition.

Data

Following intravenous administration of alvimopan to lactating rats at 10 mg/kg/day, concentrations of alvimopan and its ‘metabolite’ in the milk were approximately 15- and 0.11-fold, respectively, the concentration of alvimopan in maternal plasma at 1-hour post-dose.

8.4 Pediatric Use

Safety and effectiveness in pediatric patients have not been established.

8.5 Geriatric Use

Of the total number of patients in 6 clinical efficacy studies treated with alvimopan 12 mg or placebo, 46% were 65 years of age and over, while 18% were 75 years of age and over. No overall differences in safety or effectiveness were observed between these patients and younger patients, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out. No dosage adjustment based on increased age is required [see Clinical Pharmacology (12.3)].

8.6 Hepatic Impairment

Alvimopan is not recommended for use in patients with severe hepatic impairment.

Dosage adjustment is not required for patients with mild-to-moderate hepatic impairment. Patients with mild-to-moderate hepatic impairment should be closely monitored for possible adverse reactions (e.g., diarrhea, gastrointestinal pain, cramping) that could indicate high alvimopan or ‘metabolite’ concentrations, and alvimopan should be discontinued if adverse reactions occur [see Warnings and Precautions (5.4), Clinical Pharmacology (12.3)].

8.7 Renal Impairment

Alvimopan is not recommended for use in patients with end-stage renal disease. Dosage adjustment is not required for patients with mild-to-severe renal impairment, but they should be monitored for adverse reactions. Patients with severe renal impairment should be closely monitored for possible adverse reactions (e.g., diarrhea, gastrointestinal pain, cramping) that could indicate high alvimopan or ‘metabolite’ concentrations, and alvimopan should be discontinued if adverse reactions occur [see Clinical Pharmacology (12.3)].

8.8 Race/Ethnicity

No dosage adjustment is necessary in Black, Hispanic, and Japanese patients. However, the exposure to alvimopan in Japanese healthy male subjects was approximately 2-fold greater than in Caucasian subjects. Japanese patients should be closely monitored for possible adverse reactions (e.g., diarrhea, gastrointestinal pain, cramping) that could indicate high alvimopan or ‘metabolite’ concentrations, and alvimopan should be discontinued if adverse reactions occur [see Clinical Pharmacology (12.3)].

12.1 Mechanism of Action

Alvimopan is a selective antagonist of the cloned human µ-opioid receptor with a Ki of 0.4 nM (0.2 ng/mL) and no measurable opioid-agonist effects in standard pharmacologic assays. The dissociation of [3H]-alvimopan from the human µ-opioid receptor is slower than that of other opioid ligands, consistent with its higher affinity for the receptor. At concentrations of 1 to 10 µM, alvimopan demonstrated no activity at any of over 70 non-opioid receptors, enzymes, and ion channels.

Postoperative ileus is the impairment of gastrointestinal motility after intra-abdominal surgery or other, non-abdominal surgeries. Postoperative ileus affects all segments of the gastrointestinal tract and may last from 5 to 6 days, or even longer. This may potentially delay gastrointestinal recovery and hospital discharge until its resolution. It is characterized by abdominal distention and bloating, nausea, vomiting, pain, accumulation of gas and fluids in the bowel, and delayed passage of flatus and defecation. Postoperative ileus is the result of a multifactorial process that includes inhibitory sympathetic input and release of hormones, neurotransmitters, and other mediators (e.g., endogenous opioids). A component of postoperative ileus also results from an inflammatory reaction and the effects of opioid analgesics. Morphine and other µ-opioid receptor agonists are universally used for the treatment of acute postsurgical pain; however, they are known to have an inhibitory effect on gastrointestinal motility and may prolong the duration of postoperative ileus.

Following oral administration, alvimopan antagonizes the peripheral effects of opioids on gastrointestinal motility and secretion by competitively binding to gastrointestinal tract µ-opioid receptors. The antagonism produced by alvimopan at opioid receptors is evident in isolated guinea pig ileum preparations in which alvimopan competitively antagonizes the effects of morphine on contractility. Alvimopan achieves this selective gastrointestinal opioid antagonism without reversing the central analgesic effects of µ-opioid agonists.

12.2 Pharmacodynamics

In an exploratory study in healthy subjects, alvimopan 12 mg administered twice a day reduced the delay in small and large bowel transit induced by codeine 30 mg administered 4 times a day, as measured by gastrointestinal scintigraphy. In the same study, concomitant alvimopan did not reduce the delay in gastric emptying induced by codeine.

Cardiac Electrophysiology

At a dosage of 24 mg twice daily (two times the approved recommended dosage) for 7 days, alvimopan does not prolong the QT interval to any clinically relevant extent. The potential for QTc effects at higher doses has not been studied.

12.3 Pharmacokinetics

Following oral administration of alvimopan, an amide hydrolysis compound is present in the systemic circulation, which is considered a product exclusively of intestinal flora metabolism. This compound is referred to as the ‘metabolite’. It is also a mu-opioid receptor antagonist with a Ki of 0.8 nM (0.3 ng/mL).

Absorption

Following oral administration of alvimopan capsules in healthy plasma subjects, the alvimopan concentration peaked at approximately 2 hours post-dose. No significant accumulation in the concentration of alvimopan was observed following twice daily dosing. The mean peak plasma concentration was 10.98 (±6.43) ng/mL and mean AUC0-12h was 40.2 (±22.5) ng•h/mL after dosing of alvimopan at 12 mg twice daily for 5 days. The absolute bioavailability was estimated to be 6% (range, 1% to 19%). There was a delay in the appearance of the ‘metabolite’, which had a median Tmax of 36 hours following administration of a single dose of alvimopan. Concentrations of the ‘metabolite’ were highly variable between subjects and within a subject. The ‘metabolite’ accumulated after multiple doses of alvimopan. The mean Cmax for the ‘metabolite’ after alvimopan 12 mg twice daily for 5 days was 35.73 ± 35.29 ng/mL.

Concentrations of alvimopan and its ‘metabolite’ are higher (approximately 1.9-fold and 1.4-fold, respectively) in postoperative ileus patients than in healthy subjects.

Effect of Food: A high-fat meal decreased the extent and rate of alvimopan absorption. The Cmax and AUC were decreased by approximately 38% and 21%, respectively, and the Tmax was prolonged by approximately 1 hour. The clinical significance of this decreased bioavailability is unknown. In postoperative ileus clinical trials, the preoperative dose of alvimopan was administered in a fasting state. Subsequent doses were given without regard to meals.

Distribution

The steady-state volume of distribution of alvimopan was estimated to be 30±10 L. Plasma protein binding of alvimopan and its ‘metabolite’ was independent of concentration over ranges observed clinically and averaged 80% and 94%, respectively. Both alvimopan and the ‘metabolite’ were bound to albumin and not to alpha-1 acid glycoprotein.

Elimination

Metabolism and Excretion: In vitro data suggest that alvimopan is not a substrate of CYP enzymes. The average plasma clearance for alvimopan was 402 (±89) mL/min. Renal excretion accounted for approximately 35% of total clearance. There was no evidence that hepatic metabolism was a significant route for alvimopan elimination. Biliary secretion was considered the primary pathway for alvimopan elimination. Unabsorbed drug and unchanged alvimopan resulting from biliary excretion were then hydrolyzed to its ‘metabolite’ by gut microflora. The ‘metabolite’ was eliminated in the feces and in the urine as unchanged ‘metabolite’, the glucuronide conjugate of the ‘metabolite’, and other minor metabolites. The mean terminal phase half-life of alvimopan after multiple oral doses of alvimopan ranged from 10 to 17 hours. The terminal half-life of the ‘metabolite’ ranged from 10 to 18 hours.

Specific Populations

Geriatric Patients: The pharmacokinetics of alvimopan, but not its ‘metabolite’, were related to age, but this effect was not clinically significant and does not warrant dosage adjustment based on increased age.

Racial or Ethnic Groups: The pharmacokinetic characteristics of alvimopan were not affected by Hispanic or Black race. Plasma ‘metabolite’ concentrations were lower in Black and Hispanic patients (by 43% and 82%, respectively) than in Caucasian patients following alvimopan administration. These changes are not considered to be clinically significant in surgical patients. Japanese healthy male subjects had an approximately 2-fold increase in plasma alvimopan concentrations, but no change in ‘metabolite’ pharmacokinetics. The pharmacokinetics of alvimopan have not been studied in subjects of other East Asian ancestry. Dosage adjustment in Japanese patients is not required [see Use in Specific Populations (8.8)].

Male and Female Patients: There was no effect of sex on the pharmacokinetics of alvimopan or the ‘metabolite’.

Patients with Hepatic Impairment: Exposure to alvimopan following a single 12 mg dose tended to be higher (1.5- to 2-fold, on average) in patients with mild or moderate hepatic impairment (as defined by Child-Pugh Class A and B, n=8 each) compared with healthy controls (n=4). There were no consistent effects on the Cmax or half-life of alvimopan in patients with hepatic impairment. However, 2 of 16 patients with mild-to-moderate hepatic impairment had longer than expected half-lives of alvimopan, indicating that some accumulation may occur upon multiple dosing. The Cmax of the ‘metabolite’ tended to be more variable in patients with mild or moderate hepatic impairment than in matched normal subjects. A study of 3 patients with severe hepatic impairment (Child-Pugh Class C), indicated similar alvimopan exposure in 2 patients and an approximately 10-fold increase in Cmax and exposure in 1 patient with severe hepatic impairment when compared with healthy controls [see Warnings and Precautions (5.4), Use in Specific Populations (8.6)].

Patients with Renal Impairment: There was no relationship between renal function (i.e., creatinine clearance [CrCl]) and plasma alvimopan pharmacokinetics (Cmax, AUC, or half-life) in patients with mild (CrCl 51 to 80 mL/min), moderate (CrCl 31 to 50 mL/min), or severe (CrCl less than 30 mL/min) renal impairment (n=6 each). Renal clearance of alvimopan was related to renal function; however, because renal clearance was only a small fraction (35%) of the total clearance, renal impairment had a small effect on the apparent oral clearance of alvimopan. The half-lives of alvimopan were comparable in the mild, moderate, and control renal impairment groups but longer in the severe renal impairment group. Exposure to the ‘metabolite’ tended to be 2- to 5-fold higher in patients with moderate or severe renal impairment compared with patients with mild renal impairment or control subjects. Thus, there may be accumulation of alvimopan and ‘metabolite’ in patients with severe renal impairment receiving multiple doses of alvimopan. Patients with end-stage renal disease were not studied [see Warnings and Precautions (5.5), Use in Specific Populations (8.7)].

Patients with Crohn’s Disease: There was no relationship between disease activity in patients with Crohn’s disease (measured as Crohn’s Disease Activity Index or bowel movement frequency) and alvimopan pharmacokinetics (AUC or Cmax). Patients with active or quiescent Crohn’s disease had increased variability in alvimopan pharmacokinetics, and exposure tended to be 2-fold higher in patients with quiescent disease than in those with active disease or in normal subjects. Concentrations of the ‘metabolite’ were lower in patients with Crohn’s disease.

Drug Interaction Studies

Potential for Drugs to Affect Alvimopan Pharmacokinetics: Concomitant administration of alvimopan with inducers or inhibitors of CYP enzymes is unlikely to alter the metabolism of alvimopan because alvimopan is metabolized mainly by non-CYP enzyme pathway. No clinical studies have been performed to assess the effect of concomitant administration of inducers or inhibitors of cytochrome P450 enzymes on alvimopan pharmacokinetics.

In vitro studies suggest that alvimopan and its ‘metabolite’ are substrates for p-glycoprotein. A population pharmacokinetic analysis did not reveal any evidence that alvimopan or ‘metabolite’ pharmacokinetics were influenced by concomitant medications that are mild-to-moderate p-glycoprotein inhibitors. No clinical studies of concomitant administration of alvimopan and strong inhibitors of p-glycoprotein (e.g., verapamil, cyclosporine, amiodarone, itraconazole, quinine, spironolactone, quinidine, diltiazem, bepridil) have been conducted.

A population pharmacokinetic analysis suggests that the pharmacokinetics of alvimopan were not affected by concomitant administration of acid blockers or antibiotics. However, plasma concentrations of the ‘metabolite’ were lower in patients receiving acid blockers or preoperative oral antibiotics (49% and 81%, respectively). No dosage adjustments are necessary in these patients.

Potential for Alvimopan to Affect the Pharmacokinetics of Other Drugs: Alvimopan and its ‘metabolite’ are not inhibitors of CYP 1A2, 2C9, 2C19, 3A4, 2D6, and 2E1 in vitro at concentrations far in excess of those observed clinically.

Alvimopan and its ‘metabolite’ are not inducers of CYP 1A2, 2B6, 2C9, 2C19, and 3A4.

In vitro studies also suggest that alvimopan and its ‘metabolite’ are not inhibitors of p-glycoprotein.

These in vitro findings suggest that alvimopan is unlikely to alter the pharmacokinetics of coadministered drugs through inhibition or induction of CYP enzymes or inhibition of p-glycoprotein.

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis: Two-year carcinogenicity studies were conducted with alvimopan in CD-1 mice at oral doses up to 4000 mg/kg/day and in Sprague-Dawley® rats at oral doses up to 500 mg/kg/day. Oral administration of alvimopan for 104 weeks produced significant increases in the incidences of fibroma, fibrosarcoma, and sarcoma in the skin/subcutis, and of osteoma/osteosarcoma in bones of female mice at 4000 mg/kg/day (about 674 times the recommended human dose based on body surface area). In rats, oral administration of alvimopan for 104 weeks did not produce any tumor up to 500 mg/kg/day (about 166 times the recommended human dose based on body surface area).

Mutagenesis: Alvimopan was not genotoxic in the Ames test, the mouse lymphoma cell (L5178Y/TK+/−) forward mutation test, the Chinese Hamster Ovary (CHO) cell chromosome aberration test, or the mouse micronucleus test. The pharmacologically active ‘metabolite’ was negative in the Ames test, chromosome aberration test in CHO cells, and mouse micronucleus test.

Impairment of Fertility: Alvimopan at intravenous doses up to 10 mg/kg/day (about 3.4 to 6.8 times the recommended human oral dose based on body surface area) was found to have no adverse effect on fertility and reproductive performance of male or female rats.