Peripheral opioid receptor antagonists 

Peripheral opioid receptor antagonists bind to the peripheral opioid receptors, such as those in the gastrointestinal tract and block unwanted effects caused by opioids.

They are not able to penetrate the blood brain barrier so do not antagonize central nervous system opioid receptors, therefore the analgesic effects of opioids is not affected.

Peripheral opioid receptor antagonists are given with opioids to prevent opioid-induced constipation.

The peripherally acting μ-receptor antagonists (PAMORAs) are a class of drugs that include methylnaltrexone, naloxegol, and naldemedine. Collectively, each is approved for the treatment of OIC. PAMORAs work peripherally in the gastrointestinal tract, without impacting the central analgesic effects of opioids.

Peripherally acting μ-opioid receptor antagonists (PAMORAs) are a class of chemical compounds that are used to reverse adverse effects caused by opioids interacting with receptors outside the central nervous system (CNS), mainly those located in the gastrointestinal tract.