COMPARISON OF CUMULATIVE AND NON-CUMULATIVE TECHNIQUES TO MEASURE DOSE-RESPONSE CURVES FOR BETA-AGONISTS IN PATIENTS WITH ASTHMA

The use of a cumulative technique to obtain bronchodilator dose-response curves apparently will cause a greater response than a noncumulative technique, because sequential doses of drug will penetrate further into the lung. To test this hypothesis cumulative and noncumulative dose-response curves for inhaled isoprenaline were compared in 10 subjects with stable asthma, measuring FEV1 [forced expiratory volume in 1 s], forced vital capacity (FVC) and peak expiratory flow rate (PEFR). With both techniques there was an increased response with increasing doses of isoprenaline for all the dose-response curves except for the noncumulative PEFR response, which reached a plateau with the 20 .mu.g dose. The area under the dose-response curve for FEV1 was significantly greater after cumulative administration of isoprenaline than with the noncumulative technique. The increase in FVC and PEFR tended to be greater with the cumulative technique but the differences were not significant. The airway response to an inhaled .beta. agonist may be greater when a cumulative inhalation technique is used.