Influence of Gastric Emptying Rate on the Absorption of Cimetidine in Rats

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Abstract
Because of the absorption of many drugs from the intestine, the gastric emptying rate relates to the time of appearance of drug action. In the present study, the effects of water volume taken with the drugs, atropine, and metoclopramide on the absorption properties of cimetidine were investigated in rats. As a result the following facts were clarified; (1) the absorption rate of cimetidine was significantly influenced by water volume taken with drug, and in this case the absorption rate decreased with decreasing water volume, (2) atropine (which decreases the gastric emptying rate) decreasing absorption rate constant of cimetidine, and (3) metoclopramide (which increases the gastric emptying rate) increasing absorption rate constant of cimetidine, respectively. On the other hand, it was also clarified that the first-pass effect of cimetidine was negligible and the change of water volume taken with drug and coadministration of atropine and metoclopramide did not decrease the extent of bioavailability of cimetidine in comparison with the control. Although it is reported that antacid decreased the bioavailability of cimetidine, in the present study the effect of the antacid (formulated to the reported manner) on the absorption of cimetidine was not observed.