Loperamide but not morphine has anti-secretory effects in human colon, in vitro.

Isolated preparations of human colonic mucosa were set up in Ussing chambers. Noradrenaline reduced basal short-circuit current, morphine did not nor did loperamide except at the highest concentration tested. Electrically evoked increases in short-circuit current were unaffected by morphine but reduced by loperamide, by a naloxone-insensitive mechanism. Unidirectional fluxes of 22sodium and 36chloride were unaffected by morphine. It is concluded that loperamide but not morphine has an anti-secretory effect on human colonic mucosa.