Evaluation of the antihypertensive effect of atenolol in fixed or free combination with chlorthalidone.

A double-blind, within-patient study was carried out in 23 newly diagnosed patients with mild to moderate hypertension (diastolic blood pressure of at least 100 mmHg) to compare the antihypertensive effects of atenolol (100 mg) and chlorthalidone (25 mg) given in free and fixed combination. After a 4-week placebo run-in period, patients received each of the two active treatments and also placebo for periods of 4 weeks, the treatment sequence being randomized. A single daily drug dose was taken 24 to 28 hours before each blood pressure measurement at 2-weekly intervals. The results showed that both active drug combinations lowered lying, standing and post-exercise blood pressure significantly and there was no statistical difference between the two forms of treatment. Two-thirds of the patients were adequately controlled with the single daily dose regimen and few side-effects were reported.