Relationship between ranitidine plasma levels and reduction of postprandial intragastric acidity in healthy man.

Intragastric acidity was measured for 20 min before and 6 h 40 min after a steak meal by aspiration of small aliquots of the gastric content every 10 min in 11 healty volunteers. Administration of ranitidine hydrochloride (100 mg) at the beginning of the meal reduced postprandial acidity markedly throughout the test, but there was no correlation between the percentage reduction of acidity and the concentration of ranitidine in plasma. The effect of the drug lasted much longer than would be expected from the plasma values. The results suggest that ranitidine is cleared more rapidly from the blood than from the H2-receptors of the parietal cells, and the reduction of postprandial acidity by ranitidine cannot be deduced from the plasma values of the drug.