Methylnaltrexone

Methylnaltrexone is a quaternary ammonium derivative of naltrexone used as a peripherally acting mu-opioid receptor antagonist. Its permanently charged structure prevents crossing of the blood-brain barrier, allowing it to reverse peripheral effects of opioids—primarily opioid-induced constipation—without affecting central analgesia or inducing withdrawal in the CNS. It is marketed under the brand name Relistor for the treatment of opioid-induced constipation in patients with chronic non-cancer pain or advanced illness.

Other names

N-MethylnaltrexoneMethylnaltrexoniumMNTXNaltrexone MBRelistor (brand name)

As a drug, methylnaltrexone works as a peripherally acting mu-opioid receptor antagonist, blocking opioid effects in the GI tract.