To investigate the clinical significance of interactions between cisapride and sustained-release nifedipine, we comparedthe plasma nifedipine concentration and blood pressure after administration of nifedipine alone (20 mg) with those obtained after administration of nifedipine with cisapride (2.5 mg) in 20 patients with hypertension. The plasma nifedipine level was not altered by cisapride at one hour after administration, but was significantly increased at two (p<0.01), three (p<0.01), and four (p<0.05) hours when compared with the level measured after nifedipine alone. Cisapride significantly decreased the mean blood pressure at three hours (p<0.05) after administration ofnifedipine. The acetaminophen method was used to determine gastric emptying time. The plasma concentration of acetaminophenat 45 minutes after administration was significantly increased by cisapride, suggesting that enhanced gastrointestinal motility might be the basis for the increase in the plasma nifedipine concentration. These results suggest that enhancement of the antihypertensive effect ofnifedipine can occur when the drug is prescribed with cisapride, and that caution is needed whenusing such a combination therapy. (Internal Medicine 35: 941-945, 1996)

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