By David Douglas
WESTPORT, CT (Reuters Health) – Terbutaline sulfate given via AstraZeneca's dry powder Turbuhaler achieves greater lung deposition and bronchoprotection to asthmatics than does the same dose delivered using a pressurized metered dose inhaler (pMDI), according to European researchers.
Dr. Eric Derom of Ghent University Hospital in Belgium and colleagues sought "to further explore the concept that lung deposition data may act as a parameter for the clinical response to inhaled drugs in asthma patients."
In particular, they examined responses to histamine and methacholine challenges in patients pretreated with terbutaline via Turbuhaler and pMDI. The findings appeared in the October 15th issue of the American Journal of Respiratory and Critical Care Medicine.
In this double-blind, double-dummy, crossover study, the researchers randomized 13 asthmatics to inhalation of 0.25 or 0.5 mg of terbutaline via both devices. The concentration of methacholine or of histamine required to cause a 20% drop in lung function (FEV1) was measured before and at intervals after terbutaline inhalation.
The Turbuhaler delivered significantly more of the nominal 0.25-mg and 0.5-mg dosages (20.8% and 16.9%) than did the pMDI (4.8% and 7.4%). A 3.14 times greater pMDI dose was needed to provide the same pulmonary deposition as that achieved with the Turbuhaler.
Furthermore, a 2.1 times greater pMDI dose was required to provide a comparable degree of bronchoprotection against histamine challenge. For methacholine, the dose required was 3.2 times greater.
Commenting on the findings, Dr Derom told Reuters Health that "pulmonary deposition of an inhaled medication affects the clinical effect to a great extent." Because of this, "replacing a device with a lower deposition with one with a higher deposition should" be accompanied by "adaptation of the nominal or delivered dose prescribed by the physician."
Am J Respir Crit Care Med 2001;164:1398
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