Cholinergic effects of cimetidine and ranitidine.

Cimetidine and ranitidine were submitted to eight in vitro assays: their intrinsic activity was evaluated on guinea-pig auricles and ileum, acetylcholine synergism on guinea-pig tracheal muscle, frog rectus abdominis, guinea-pig vas and rat phrenic nerve diaphragm, and antagonism on guinea-pig auricles and rat jejunum estimated at a range of concentrations. Ranitidine alone opposed 1-hyoscyamine antagonism in guinea-pig ileum when acetylcholine was the agonist, but not when the agonist was bethanechol.