Bronchial responsiveness to inhaled propranolol in asthmatic children and adults

Abstract

Inhaled propranolol (P) was administered to a population which included asthmatic children (30 subjects) and adults (43 subjects): 1) to investigate the determinants of induced bronchial response; 2) to examine the relationship with treatment requirements; 3) to determine the relationship with responsiveness to methacholine (M) and ultrasonically nebulized distilled water (UNDW) (50 subjects); and 4) to establish the short-term repeatability of bronchial response to propranolol compared with methacholine (22 subjects). Bronchial response to propranolol and methacholine was expressed as the cumulative provocative dose (PD20 in μmol) and responsiveness to UNDW as the provocative output (PO20 in ml · min-1) producing a 20% fall in forced expiratory volume in one second (FEV1). Response to propranolol was significantly related to the degree of responsiveness to methacholine, but not to age, gender, presence of atopy, age at asthma onset, or baseline FEV1. PD20P was measurable in all but three subjects. A significant difference in mean PD20M but not in PD20P was found between subjects requiring more anti-asthmatic treatments compared to those without therapy. The difference between geometric mean PD20P and geometric mean PD20M was 14.1. PO20UNDW was measurable in only 21 out of 50 subjects. Both PD20P and PD20M were significantly lower in responders to UNDW than in nonresponders. Reproducibility of PD20P was comparable to that of PD20M (coefficients of repeatability: 1.17 and 1.09). We conclude that bronchial responsiveness to propranolol is safely measurable in most children and adults with asthma. Repeatability of bronchial response to propranolol is comparable to that of methacholine. Moreover, responsiveness to propranolol is not a predictor of treatment requirement. In general, inhaled propranolol is a less potent bronchoconstrictive drug than methacholine. Although, responsiveness to propranolol seems to reflect the degree of nonspecific bronchial hyperresponsiveness, bronchial sensitivity to methacholine did not predict that to propranolol.