Peripherally acting [micro]-opioid receptor antagonists as treatment options for constipation in noncancer pain patients on chronic opioid therapy

Opioid-induced constipation (OIC), a prevalent and distressing side effect of opioid therapy, does not reliably respond to treatment with conventional laxatives. OIC can be a treatment-limiting adverse event. Recent advances in medications with peripherally acting [micro]-opioid receptor antagonists, such as methylnaltrexone, naloxegol, and alvimopan, hold promise for treating OIC and thus extending the benefits of opioid analgesia to more chronic pain patients. Peripherally acting [micro]-opioid receptor antagonists have been clinically tested to improve bowel symptoms without compromise to pain relief, although there are associated side effects, including abdominal pain. Other treatment options include fixed-dose combination products of oxycodone analgesic together with naloxone. Keywords: opioid-induced constipation, opioid bowel disorder, PAMORA, peripherally acting mu-opioid receptor antagonist, noncancer pain patients, opioid-associated side effects