Variation of Drug Action on Airway Obstruction in Man

Rapid and sustained relief of airway obstruction is a therapeutic aim which is still only rarely achieved in chronic bronchitis or asthma.Although the topical administration of adrenergic smooth muscle relaxants usually affords a rapid symptomatic improvement in these patients, the duration of relief is limited, and the efficacy of this treatment diminishes as breathlessness increases.There is clearly a need for more effective and longer lasting drugs.This communication is primarily concerned with the variations that were observed in the response to aerosols of isoprenaline sulphate and atropine methonitrate after their administration to patients at different phases of airway obstruction.The protective action of some drugs against artificially induced airway obstruction was also investigated. METHODS AND MATERIALS ESTIMATION OF AIRWAY RESISTANCE Serial F.E.V.and vital capacity values were determined by the author using the same direct writing spirometer throughout.A minimum of three F.E.V.1 recordings were determined for each test before estimating the slow vital capacity, after which a further one to three F.E.V.1 estimations were repeated.The results were plotted to indicate the order of each attempt.When the values progressively diminished, as usually occurred during acute phases of airway obstruction, the F.E.V.1 was calculated as the average of the last three attempts.In the majority of cases, consecutive F.E.V.1 values were similar or increased during the first few attempts; in these circumstances the average of the three highest values was calculated as the F.E.V.1.DRUG ADMINISTRATION Drug administration was carried out under strict supervision; aerosols were administered in rooms set aside for this purpose, and only one type of drug was administered in each room.Patients received no isoprenaline for three hours, and no atropine for 12 hours, before tests.All aerosol drugs were administered from a Wright nebulizer operating on compressed air, and a different set of apparatus was used for each type of drug.Aqueous solutions usually contained 5% propylene glycol (0-2% sodium metabisulphite was also included in the stock solutions containing isoprenaline).AEROSOL DOSE The weight loss from the nebulizer PROCEDURE FOR ASSESSING DRUG ACTION An increased airway resistance was induced by the aerosol admini- 406 copyright.