β2-agonists administered by a dry powder inhaler can be used in acute asthma

Patients with acute asthma attending the emergency room were included in a double-blind, double-dummy and parallel group study to investigate whether a dry powder inhaler (Turbuhaler (R)) can be used in acute asthma. If so, the aim was to establish the potency relationship between a beta(2)-agonist (salbutamol) administered by the dry powder inhaler and the pressurized metered-dose inhaler (pMDI). Eighty-six patients with a mean age of 38 years and forced expiratory volume in 1 s (FEV1) of 37% of predicted normal value were randomized at Siriraj Hospital in Bangkok to either Turbuhaler (50 mu g dose(-1)) or pMDI (100 mu g dose(-1)) with spacer (Volumatic (R)). Doses of 100+300+300+300 mu g salbutamol were given at 0, 15, 30 and 45 min via Turbuhaler and repeated at 90, 105, 120 and 135 min (total dose 2000 mu g). The same inhalation schedule with identical number of doses was used for the pMDI with spacer but in double doses (total 4000 mu g), assuming a dose-potency ratio of salbutamol administered via Turbuhaler compared with the pMDI of 2:1. At 85 min after the first dose, 60 mg prednisolone was given orally. FEV1 was measured 10 min after each dosing. Peak inspiratory flow (PIF) through Turbuhaler was measured on each dosing occasion. Plasma (P)-salbutamol, serum (S)-potassium concentrations, pulse rate, blood pressure and adverse events were recorded. No statistically significant differences were observed in the increase in FEV1 between the groups: 55 min (165 min) after the first dose, the increase was 0.471 and 47% (0.641 and 63%) in the Turbuhaler group, and 0.461 and 42% (0.681 and 65%) in the pMDI group. Mean PIF though Turbuhaler was 491 min(-1) (range 26-68) at first inhalation and increased to 601 min(-1) (range 38-86). There was no correlation between the initial PIF through Turbuhaler and the initial FEV1 response. P-salbutamol and S-potassium values correlated well. A larger decrease in S-potassium was noticed after 75 min in the pMDI group (0.38 mmol 1(-1)) compared with the Turbuhaler group (0.23 mmol 1(-1)) (P=0.02). In conclusion, the use of a dry powder inhaler, Turbuhaler, was investigated in the emergency room treatment of acute asthma, and was as effective as a pMDI with spacer. Half the dose of salbutamol administered via Turbuhaler was as effective as the full dose given via a pMDI with spacer.