Pharmacokinetics of ranitidine and nizatidine in very elderly patients.

This study was undertaken to examine whether the pharmacokinetic profiles of ranitidine and nizatidine, the H2 antagonists, differed with repeated doses in very elderly patients (>80 years old). Ranitidine (150 mg) or nizatidine (150 mg) was given twice daily in 10 very elderly female patients for 14 days. This study was a randomized, crossover design with a wash-out period of 14 days. Pharmacokinetic profiles were determined after first (on day 1) and 27th (on day 14) doses of each agent. The maximum plasma drug concentration (Cmax) and area under the plasma drug concentration-time curve (AUC) were significantly greater after the 27th than after the first dose in the ranitidine but not in the nizatidine trials. The accumulation of ranitidine in plasma tended to be greater than that of nizatidine. These results suggest that nizatidine is safer for the repeated treatment in very elderly patients.