Peripherally acting μ-opioid receptor antagonist

Peripherally Acting μ-Opioid Receptor Antagonists (PAMORAs) are a class of drugs that act on the μ-opioid receptors located in the peripheral nervous system. These drugs are primarily used to treat opioid-induced constipation (OIC), a common side effect of long-term opioid therapy.

Mechanism of Action

PAMORAs work by blocking the μ-opioid receptors in the gastrointestinal tract. Opioids, while effective for pain management, often cause constipation by binding to the μ-opioid receptors in the gut. This slows down the movement of the bowel and reduces the amount of fluid in the stool, leading to constipation. By blocking these receptors, PAMORAs prevent opioids from affecting the gastrointestinal tract, thereby alleviating constipation without affecting pain management.

Examples of PAMORAs

There are several drugs in the PAMORA class, including:

• Naloxegol: Naloxegol is a PAMORA that is used specifically for the treatment of OIC in adults with chronic non-cancer pain.
• Methylnaltrexone: Methylnaltrexone is used to treat OIC in adults with advanced illness who are receiving palliative care.
• Alvimopan: Alvimopan is used to accelerate the time to upper and lower gastrointestinal recovery following surgeries that include partial bowel resection with primary anastomosis.

Side Effects

Like all drugs, PAMORAs can have side effects. These can include abdominal pain, diarrhea, nausea, and gas. In rare cases, PAMORAs can cause more serious side effects like severe stomach pain or diarrhea, or symptoms of opioid withdrawal.

See Also

• Opioid
• Opioid receptor
• Constipation
• Gastrointestinal tract

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