[Comparison of the characteristics of methacholine and of propranolol in the assessment of aspecific hyperreactivity of the airways].

Quantitative bronchial challenge tests with methacholine and propranolol were performed in volunteers with bronchial asthma (n = 17) and in normal controls (n = 13), in order to test the earlier assumption that propranolol might be more useful to assess nonspecific bronchial responsiveness in bronchial asthma. The investigations were performed in random order, with a minimum interval of 24-hours. The aerosol was administered by a dosimeter (APS, Jaeger), using doubling concentrations, with a maximum of 25 mg/ml (2.5%), the lowest concentrations being 0.26 mg/ml (propranolol) and 0.03 mg/ml (methacholine), respectively. The provocation dose at a decrease in sGaw of 50% (PD50) was calculated from the dose-response curve. While methacholine induced an airways obstruction sufficient to calculate a PD50 in 29/30 subjects, propranolol was similarly effective in only 19/30 cases the rank correlation coefficient was 0.4368 (p less than 0.025). At a methacholine-PD50 greater than 0.2 mg(= concentration greater than 1 mg/ml) no propranolol-PD50 could be determined. In accordance with the literature, in the asthmatic subgroup the PD50sGaw [geometric means] were 25 (2.7-109.6) micrograms for methacholine, and 900 (75.9-3331) micrograms for propranolol, or 0.13 mumol and 3.46 mumol, respectively. The inhalation of propranolol in the highest possible concentration (limited solubility) induced airways obstruction only in subjects with asthmatic hyper-responsiveness. A similar distinction between asthmatic and normal subjects is possible by methacholine using a threshold concentration (in this study: cumulative PD50sGaw 0.2 mg or provocation concentration 1 mg/ml). Moreover, methacholine allows a determination of minor degrees of hyperresponsiveness, in mild airways obstruction or normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)