Methylnaltrexone (Bromide)

Methylnaltrexone (Bromide) is a peripheral-acting opioid receptor antagonist that acts on the gastrointestinal tract to decrease opioid-induced constipation.

In Vivo: Methylnaltrexone bromide (1 and 10 mg/kg, s.c.) has no effect on tyrosine-induced analgesia. Intracerebroventricular injection of Methylnaltrexone bromide (1 and 10 mg/rat) effectively blocks tyrosine-induced analgesia^[1]. Methylnaltrexone bromide (0.01-10.00 mg/kg), does not significantly influence retention latencies of either shocked or unshocked mice. Further, Methylnaltrexone bromide (0.1, 1.0, or 10.0 mg/kg) does not block the retention impairment produced by concurrently administered morphine (3.0 mg/kg) or beta-endorphin (0.1 mg/kg)^[2].