Assessment of beta‐adrenoceptor antagonists in asthmatic patients.

Abstract

1 Bronchial smooth muscle, skeletal muscle and cardiac 13-adrenoceptor antagonism have been compared in twelve asthmatic patients after three 0-adrenoceptor antagonists at two dose levels. The non-selective antagonist propranolol (40 and 160 mg), the non-selective antagonist with partial agonist activity pindolol (5 and 20mg) and the Pl-selective antagonist atenolol (50 and 200 mg) were studied on separate occasions. 2 Six placebo days were used in this double-blind crossover study to allow interpretation of individual as well as group results. 3 Bronchial smooth muscle effects were assessed by resting spirometry, histamine inhalation test and spirometric response to inhaled fenoterol. Skeletal muscle effects were assessed by resting tremor and fenoterol induced tremor.4 Cardiac P-adrenoceptor antagonism was assessed by measuring the effect on resting heart rate and on maximum heart rate in a standard exercise test. 5 Pindolol tended to cause least change from placebo in resting spirometry, caused significant tremor response, inhibited the fenoterol airway response, and tended to protect against inhaled histamine. 6 Atenolol 50 mg was the only drug to allow a fenoterol airway response similar to placebo. Atenolol increased the inhaled histamine responsiveness. 7 Propranolol 160 mg caused the most reduction in spirometry but also tended to cause the maximum reduction in exercise heart rate. Propranolol caused increased inhaled histamine responsiveness. 8 Initial sensitivity to inhaled histamine did not necessarily predict significant reduction in an asthmatics' spirometry by a j3-adrenoceptor antagonist. The effect of a 3-adrenoceptor antagonist on histamine responsiveness does not correspond to its effect on inhaled 132-adrenoceptor agonist responsiveness.

Effects of acute and chronic administration of β-adrenoceptor ligands on airway function in a murine model of asthma

“…When administered acutely, they increased AR, whereas chronically, they significantly decreased the maximal constrictor response to methacholine. Whereas the acute effects of nadolol and carvedilol are in line with the reported effects of single-dose administration of nonselective ␤-blockers such as propranolol or timolol to asthmatic subjects (33) and various animal models (34)(35)(36)(37), the long-term effects of these drugs on airway responsiveness represent a major finding that could have therapeutic implications. It is noteworthy that a similar timedependent opposite effect has also been observed with certain ␤-blockers in the treatment of CHF.…”

Beta-adrenergic receptor blockers. Adverse effects and drug interactions.

“…39 Comparative studies have shown, though, that /3-blocking compounds with partial agonist activity, 40 0,-selectivity, 41 -42 and a-adrenergic blocking actions 43 are less likely to increase airways resistance in asthmatics than propranolol. /3,-Selectivity, however, is not absolute and may be lost with high therapeutic doses as shown with atenolol and metoprolol.…”

Pharmacology and Therapeutics of Bronchodilators

“…Binding studies show that approximately 70% of pulmonary ␤-ARs are of the ␤ 2 -AR subtype. These receptors are localized to ASM (3-4 ϫ 10 4 per cell), epithelium, vascular PHARMACOLOGY AND THERAPEUTICS OF BRONCHODILATORS 453 smooth muscle, and submucosal glands (Ruffin et al, 1982;Carstairs et al, 1985), whereas ␤ 1 -ARs in the lung are confined to glands and alveoli. There is a uniform distribution of ␤-ARs on the alveolar wall with a 2:1 ratio of ␤ 1 /␤ 2 -ARs (Mak et al, 1996).…”