A controlled study on the anti-hypertensive effect of a new beta-adrenoreceptor-blocking drug, metoprolol, in combination with chlorthalidone.

1. A double-blind cross-over evaluation of the anti-hypertensive effect of metoprolol vs placebo was carried out in a series of twenty-three patients with mild or moderate essential hypertension who were receiving 25 mg of chlorthalidone daily as their basic treatment. An individually determined dose of metoprolol (75-300 mg) was used. 2. Metoprolol, as compared with placebo, produced a statistically significant reduction of blood pressure, both in supine and standing positions. 3. During the double-blind cross-over study mild side effects were more common at the beginning of metoprolol/chlorthalidone treatment than during placebo/chlorthalidone, but these tended to diminish or disappear with time. 4. Metoprolol in combination with chlorathalidone appears to be an effective and well-tolerated treatment for mild and moderate hypertension in patients not responding to chlorthalidone alone.