Tiotidine and cimetidine--kinetics and dynamics.

Tiotidine and cimetidine kinetics and dynamics were compared to assess mechanisms of the longer duration of effect of tiotidine in man. Both drugs has similar lag times for absorption. Tiotidine with a meal was more slowly absorbed than when fasting and was also more slowly absorbed than cimetidine with a meal. The elimination rates for both drugs did not differ; they were both approximately 2 to 3 hr. Oral doses of cimetidine achieved areas under the plasma concentration curve approximately three times that of tiotidine but these concentrations were only 1/10 as potent. The cimetidine concentration inducing 50% inhibition of food-stimulated gastric acid secretion was 0.41 +/- 0.04 whereas it was 0.04 +/- 0.003 microgram/ml for tiotidine. The effect of tiotidine lasted longer than that of cimetidine because the doses recommended for use in man resulted in higher concentrations in plasma relative to effective concentration than clinical doses of cimetidine.