COMPARISON OF TERBUTALINE AND PLACEBO FROM A PRESSURIZED METERED-DOSE INHALER AND A DRY POWDER INHALER IN A SUBGROUP OF PATIENTS WITH ASTHMA

Background - Reversibility after administration of an inhaled bronchodilator is not always demonstrable in patients with asthma. Bronchodilator aerosol-induced bronchoconstriction has also been reported to occur in some patients. Methods - Fifteen selected patients showing <10% improvement in forced expiratory volume in one second (FEV(1)) when tested with four doses of salbutamol (0.1 mg/dose) or terbutaline (0.25 mg/dose) from a pressurised metered dose inhaler ((MDI) participated in two randomised, double blind studies. They received 2.0 mg terbutaline (4 x 2 doses of 0.25 mg) or a corresponding placebo from an MDI connected to a 750 ml spacer, and 1.0 mg (2 x 0.5 mg) terbutaline or placebo from a multidose dry powder inhaler free of additives (Turbohaler). Results - Inhalation of placebo MDI resulted in a mean (SD) decrease in FEV(1) of 20.5 (14.1)% (range -42.9% to +2.6%). In 14 patients inhalation of 2.0 mg terbutaline MDI with spacer resulted in <10% improvement (mean increase 3.1 (6.0)%). One mg of terbutaline via a Turbohaler resulted in improvements in FEV(1) of >15% in eight patients (mean increase 16.0 (9.7)%). The improvement was <10% in four patients. Use of placebo Turbohaler did not affect airway calibre (mean change 0.2 (2.9)%). Conclusions - Additives of MDIs may cause bronchoconstriction in some patients with asthma. In these patients inhalation from a pressurised metered dose inhaler is more likely to decrease the bronchodilator response than inhalation from an additive-free inhaler. The frequency of this phenomenon is unknown.