Oral naloxone antagonizes loperamide-induced delay of orocecal transit

Orocecal transit time was determined by the lactulose hydrogen breath test in nine healthy volunteers after administration of placebo, loperamide (16 mgper os), and loperamide (16 mgper os) followed by oral naloxone at doses of 16 and 32 mg. The four tests were performed in double-blind conditions and in random sequences. Transit time (mean,sd) after loperamide (128.8 min, 32.9) was significantly increased (P<0.05) compared with placebo (85.5 min, 35.7), loperamide followed by naloxone 16 mg (88.8 min, 46.2), and loperamide followed by naloxone 32 mg (84.4 min, 40.6). These results show that the peripheral opioid agonist loperamide delays orocecal transit in healthy subjects and that naloxoneper os at adequate doses antagonizes this effect.