Pharmacokinetics of atenolol in hypertensive subjects with and without co-administration of chlorthalidone

The pharmacokinetics of atenolol with and without the co-administration of chlorthalidone were studied in five hypertensive subjects. Concomitant administration of chlorthalidone appears to have little if any effect on the pharmacokinetics of atenolol during treatment for 7 days. The atenolol elimination half-lives were 6.7 +/- 1.1 and 6.3 +/- 0.9 h, respectively, with and without chlorthalidone. Two healthy volunteers also received a single 50 mg oral dose of chlorthalidone. Their blood profiles and pharmacokinetics were similar to those observed in hypertensive subjects, but a statistically significant difference (p < 0.01) was found between the urinary excretion half-lives of chlorthalidone. This difference may be because chronic administration of the drug caused saturation of red cell binding.