FDA Approves Movantik for Opioid-induced Constipation
Opioid-induced constipation is a well-known and persistent side effect of chronic opioid use. The gastrointestinal tract contains mu opioid receptors. When a person takes an opioid, the medication binds to these receptors in the GI tract, reducing motility, making bowel movements difficult and causing patients to strain, have hard or lumpy stools or experience a sensation of incomplete evacuation.
Because Movantik, which is distributed by AstraZeneca, is a mu opioid receptor antagonists, it decreases the constipating effects of opioids. “Supportive care products such as Movantik can lessen the constipating side effects of opioids,” said Julie Beitz, MD, director of the Office of Drug Evaluation III in the FDA’s Center for Drug Evaluation and Research.
How it Was Approved
Movantik’s safety and effectiveness were established in two clinical trials of 1,352 participants who had taken opioids for at least 4 weeks for non-cancer related pain and had opioid-induced constipation. Participants were randomly assigned to receive 12.5 mg or 25 mg of Movantik or placebo once daily for 12 weeks. The trials were designed to measure the change in the number of bowel movements per week from the start of the study.
Results of the first trial showed that 44% of participants receiving 25 mg of Movantik and 41% of participants receiving 12.5 mg of Movantik experienced an increase in bowel movements per week, compared to only 29% of control patients. A second trial showed similar results.
Common side effects of Movantik include abdominal pain, diarrhea, headache and the experience of excessive gas in the stomach or intestinal area (flatulence.
The FDA is requiring a postmarketing study to further evaluate the potential risk of cardiovascular adverse events in patients taking Movantik. In June, the FDA held a public meeting to discuss what studies might be required to assess the cardiac safety of peripherally acting opioid receptor antagonists, including Movantik, intended to treat opioid-induced constipation.
Other OIC Products
Movantik enters a growing market of medications for opioid-induced constipation. In 2008, the FDA approved Relistor (methylnaltrexone bromide). Both Relistor and Movantik are peripherally acting mu opioid receptor antagonists, however Relistor differs from Movantik in that it is given subcutaneously. The usual schedule is one dose every other day, as needed. In approving Relistor, the FDA noted that "This new drug will be helpful to patients who experience severe constipation associated with the continuous use of morphine or other opioids, which are an important part of care for patients with late-stage, advanced illness."