Cimetidine plasma concentration-response relationships

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Abstract
Cimetidine plasma concentration-response relationships were investigated in 6 healthy subjects using suppression of gastric acid secretion under continuous pentagastrin stimulation (1.5 .mu.g/kg per h) as a test model. With the Hill equation the sigmoid was preferable to the linear relationship between plasma concentration and effect, and there were significant correlations with P values under 0.01 in all but 1 subject. From the individual curves a mean plasma level of 0.78 .mu.g/ml (range 0.54-1.04 .mu.g/ml) for 50% inhibition of gastric acid secretion was determined; mean concentration for 90% inhibition was calculated to be 3.9 .mu.g/ml. The model described should allow determination of whether different patient populations (e.g., healthy subjects, patients with ulcers, male and female patients, patients with renal or liver disease) differ from 1 another in concentration-response relationships to histamine H2 receptor antagonists; if so, appropriate drug plasma levels should be achieved for specific degrees of inhibition of gastric acid secretion.