Ranitidine increases the bioavailability of nitrendipine in patients with arterial hypertension

1. In a randomized placebo-controlled study, 12 hypertensive patients were treated po for one week with 20 mg nitrendipine once daily plus placebo, twice daily and later with the same dose of nitrendipine plus 300 mg ranitidine (150 mg twice a day). 2. When ranitidine was coadministered, plasma nitrendipine levels (0-24 h) were significantly increased (P < 0.001), although no significant increase in peak plasma nitrendipine level (Cmax) was observed due to the wide range of variation of this parameter (Cmax) in hypertensive patients. 3. Ranitidine coadministration increased the area under the curve for 24-h (AUC0-24) plasma concentration vs time, from 49.07 +/- 6.28 micrograms.h/l to 82.35 +/- 2.57 micrograms.h/l (P < 0.01). This significant increase caused a reduction in total body clearance from 2008.33 +/- 246.33 to 1284.00 +/- 182.16 ml/min (P < 0.002). 4. Nitrendipine bioavailability was increased by 89% when ranitidine was coadministered but the kinetic effect of this drug interaction is unlikely to be of clinical relevance since no adverse effects were observed in patients evaluated after ranitidine association.