SELECTED ARTICLES FROM THE RECENT LITERATURE 2005

10/26/05

Tolerance to bronchodilation by salbutamol during treatment with long acting beta agonist

Summary
Background – Additional therapy with inhaled long-acting beta agonists (LABA) such as salmeterol (Sal) and formoterol (Form) has allowed control of persistent asthma at lower doses of inhaled corticosteroids (ICS). However, some studies have found that the bronchodilation induced by salbutamol (albuterol) is decreased in individuals being treated daily with Sal for at least one week.

Findings – Haney and Hancox compared effects of one week of treatment with inhaled Form 12 mcg or placebo b.i.d. on the subsequent bronchodilating effect of inhaled albuterol (Alb) following methacholine-induced bronchoconstriction. Alb was inhaled at 5 minute intervals at cumulative doses of 100, 200 and 400 mcg.

They found a significantly lower (48%) dose bronchodilation response to Alb in asthmatics following a week of Form therapy than after placebo therapy. This pattern was still present when the analyses were adjusted for the pre-FEV1 levels and dose of methacholine used in individual subjects.

Reference
 Respir Res 2005;6:107

Editor's Comments
The authors of this report concluded that clinically relevant tolerance to rescue use of Alb in acute asthma flares is likely to occur in patients treated chronically with LABA such as Form. I agree that the findings described above are generally similar to that during chronic Sal therapy, as already reported. However, I am not sure that these findings translate into worse outcomes during Alb treatment of acute asthma flares in patients already on chronic treatment with LABA. However, some studies have suggested that the blunted bronchodilating effect of Alb in such situations may depend on genetically based alterations in the beta-adrenergic receptor.

 

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