The effect of different concentrations of lactose powder on the airway function of adult asthmatics

Lactose is widely used as a carrier of drugs in inhalation devices for asthmatic patients, but some clinicans have suspected that it may cause bronchoconstriction. Only a few studies have been done to examine this and the results are not uniform. This study was conducted to determine the effects of inhalation grade lactose delivered by Diskhaler(TM) on lung function and airway conductance in asthmatic subjects. The effect of five doses of lactose ranging from 6.25 mg to 100 mg and placebo were investigated using spirometry and constant volume plethysmography, Nineteen subjects (nine females) with stable asthma and a proven reversibility of at least 12% in forced expiratory volume in 1 sec (FEV1) (compared to baseline) in the last 6 months, were included in this single-centre, randomized, placebo-controlled, double-blind, cross-over study The subjects received placebo plus five doses of lactose on one study day and six doses of placebo on another study day. Both doses and study days were assigned in a random order, and intervals of 1 h were allowed between each dose and at least 36 h between study days. Specific airways conductance (sG(aw)) and FEV1 were measured periodically over the course of 1 h after each dose of lactose or placebo. Administration of lactose at four or eight times the concentration in the Diskus(TM) and Diskhaler(TM) dry powder inhalers did not result in any statistically significant changes in FEV1. sG(aw) also showed no statistical difference between lactose and placebo at 1 or 3 min post-dosing. Both placebo and lactose produced both dilatation and constriction of the airways in the same patients, with no consistency in direction and no dose-response relationship. No adverse effect of lactose on airways conductance or FEV1 of stable asthmatic patients was found in this study when given at higher than normal clinical doses. (C) 2001 Harcourt Publishers Ltd.