Loperamide--an opiate receptor agonist with gastrointestinal motility effects.

Loperamide is an opiate agonist, also exerting activity by inhibiting the action of calmodulin. The mode of action in the clinic is probably mainly due to its action on opiate receptors, since the effects of loperamide can be reversed by naloxone. The exclusive action in the gut is explained by the specific distribution of loperamide with extensive distribution to the gut and minimal influence on opiate receptors in CNS. Loperamide is well absorbed after oral administration and extensively metabolized. The pharmacokinetic properties are linear over a wide dose range.