GASTROENTEROLOGY ARTICLE OF THE WEEK
May 21, 2009
Becker G, Blum HE. Novel opioid antagonists for opioid-induced bowel dysfunction and postoperative ileus. Lancet 2009;373:1198-1206
1. Methylnaltrexone
a. Does not cross the BBB
b. Diminishes the GI effects of opioids by blocking the d receptors
c. Causes papillary constriction
d. May reduce post-op urinary retention when given IV
e. Main adverse event is orthostatic hypotension which is common at the recommended dose
2. Alvimopan
a. Can be given orally
b. Does not cross the BBB
c. It is a m-receptor antagonist and has higher affinity than methylnaltrexone
d. It has a high oral bioavailability
e. Has an active metabolite produced by the gut flora
True or False
3. The kappa receptors are the main receptors involved in opioid-induced gastrointestinal effects.
4. Methylnaltrexone has some m-receptor agonist activity while almivopan has no agonist activity and seems to have a higher pharmacological potency than methylnaltrexone.
5. Opioids potentiate iNOS, increasing the NO released by PMN’s infiltrating the gut wall after abdominal surgery and prolonging post-op ielus
6. Erythromycin is an effective therapy for post-op ileus
7. Alvimopan should not be used in patients who have a fresh enteric anastomosis