Methylnaltrexone (MNTX) was invented to reverse the constipation caused by powerful opioid-based pain relievers such as morphine, OxyContin or Percocet taken by patients with cancer or AIDS. Opiates also appear to increase the ability of HIV to infect certain immune system cells.
This laboratory study found that MNTX blocked increases in HIV entry and replication that occur when immune cells are exposed to therapeutic doses of morphine. In this in-vitro study, very small amounts of methylnaltrexone blocked this process.
"If our studies are borne out in future clinical trials, methylnaltrexone may improve the care of patients who take opioids for pain caused by AIDS," said Jonathan Moss, M.D., Ph.D., professor of anesthesia and critical care at the University of Chicago and director of the study.
Many AIDS patients and more than 500,000 patients with advanced cancer depend on drugs like morphine for pain relief. One side effect of these pain relievers is severe constipation, which can be so distressing that many patients discontinue their pain medication.
Methylnaltrexone was invented to solve this problem by the late Leon Goldberg, a University of Chicago pharmacologist. To help a dying friend with morphine-induced constipation, Goldberg took naltrexone, an established drug that blocks the effects of morphine, and altered it slightly so that it could no longer cross the protective barrier that surrounds the brain.
Consequently, it did not interfere with morphine's effect on pain, which is centered in the brain, but it did block morphine's effects on gut motility, which a
Contact: John Easton
University of Chicago Medical Center