The effect of metoprolol and practolol on lung function and blood pressure in hypertensive asthmatics

1 The effect of metoprolol, a new β₁-adrenoceptor blocking agent, was compared to practolol in the treatment of hypertension in seventeen asthmatics during concurrent optimum bronchodilator therapy with a selective β₂-adrenoceptor-stimulant.

2 The two β-adrenoceptor antagonists were given at two dose levels, practolol (200 mg and 400 mg) daily, and metoprolol (100 mg and 200 mg) daily, in a twice-daily dosage schedule, at 12 h intervals, for 17 days. The comparison was made double-blind and a crossover design was used. The drugs were given in randomized order. The study started with a run-in placebo period and there was a washout period on placebo between the treatment periods. Spirometry, blood pressures and heart rates were recorded in a standardized manner.

3 At the lower dose levels no influence on FEV₁ was noted, and no difference was found between the two active drugs. At the higher dose level FEV₁ was reduced by both β-adrenoceptor-blocking drugs. Four out of twelve patients given the higher dose experienced exacerbation of their asthma. The heart rate fell with both drugs and at both dose levels. During the placebo period a marked increase of heart rate was noted. The blood pressure fell at both dose levels compared to placebo, no difference being recorded between the two drugs.

4 Metoprolol and practolol are equally effective β₁-adrenoceptor blocking drugs. In this study it was found that metoprolol could be used in asthmatics who had indications for β-adrenoceptor blockade, provided that the total daily dose did not exceed 100 mg. Optimal bronchodilator treatment with a bronchoselective β-adrenoceptor agonist is an absolute prerequisite in order to avoid the risk of aggravation of asthma.