Ventilatory effects of ordinary and slow-release tablets of metoprolol in asthmatic patients.

The effect of the beta 1-selective adrenoceptor blocker, metoprolol, on ventilatory function was studied in eight asthmatic patients in relation to the plasma level of the agent following its administration in ordinary and slow-release tablets. Metoprolol causes a slight decrease in ventilatory function as compared with placebo. The effect was most pronounced after administration of 200 mg in ordinary tablets, which induced the highest plasma levels. After administration of 200 mg in slow-release tablets the plasma levels were lower and the ventilatory effect was less marked. The bronchial obstruction largely improved after administration of the beta 2-receptor stimulating agent terbutaline. This study indicates, that when a larger dose of metoprolol is used in patients with obstructive lung disease, slow-release durules are to be preferred to ordinary tablets.