Long-term effects of formoterol and salbutamol on bronchial hyperreactivity and beta-adrenoceptor density on lymphocytes in children with bronchial asthma

Abstract

Long-term treatment with short-acting beta 2-sympathomimetic drugs has recently been suggested to be due to a rise in asthma mortality. This effect has been attributed to an increase in bronchial hyperreactivity, a desensitization of beta 2-adrenoceptors and/or a rebound effect after cessation of the therapy. Formoterol, a new long-acting beta 2-symathomimetic drug, has been reported to possess not only bronchodilatation but also antiinflammatory effects. The aim of the present study was to investigate whether long-term effects of salbutamol and/or formoterol could deteriorate asthma management. Therefore, in a trial lasting 90 days, we evaluated the effects of the two drugs on lung function, on the protection they provided against inhalative provocation with histamine, and on tachyphylaxis as monitored by the beta-adrenergic density on mononuclear leukocytes (MNL). Two groups of 11 children each with stable asthma were treated with daily doses of either 4 x 200 micrograms salbutamol or 2 x 24 micrograms formoterol in monotherapy. The lung function was measured six times during the trial period, on day 1, and on day 90, before and after inhaling the drug and at all investigations both with and without histamine provocation. In both groups, the bronchodilatory effect of either formoterol or salbutamol remained constant. The lung function values before and after drug inhalation (specific airway resistance sRAW, forced expiration volume FEV1, vital capacity VC) did not alter significantly. After histamine provocation, the protection was more pronounced in the formoterol group. No changes in the beta-adrenoceptor density on MNL and no significant side effects were seen throughout the trial period. We therefore conclude that formoterol protects significantly better against the bronchial challenge with histamine than does salbutamol. Both drugs did not deteriorate the lung function in asthmatic children. In addition, there was no evidence that long-term treatment leads to a desensitization of beta 2-sympathomimetic effects.