NEW YORK (Reuters Health) - New findings suggest that the rescue response to salbutamol in the setting of acute asthma may be blunted following treatment with formoterol or salmeterol combination inhalers, regardless of the patient’s beta2 adrenoceptor genotype-16.
“Clinicians prescribing these combination inhalers need to warn their patients that they may need to use more salbutamol if they have an acute attack,” study leader Dr. Brian J Lipworth from Ninewells Hospital and Medical School, University of Dundee, Scotland, told Reuters Health.
In the August issue of the journal Thorax, he and colleagues note that the “development of tolerance following the use of long acting beta2 agonists in asthmatic patients with either the homozygous arginine (Arg-16) or glycine (Gly-16) genotypes is poorly understood.” This is especially true with respect to the acute reliever response to salbutamol in constricted airways.
They therefore investigated, in 20 patients homozygous for either Arg-16 or Gly-16, the acute response to salbutamol following methacholine bronchial challenge between the first and last doses of combination inhalers (formoterol plus budesonide or salmeterol plus fluticasone propionate).
For both genotypes, pre-challenge FEV1 values did not differ significantly between the first and last doses of each treatment. However, salbutamol recovery following methacholine challenge was significantly delayed (p < 0.05) to a similar degree in both genotypes and with both treatments “due to cross tolerance induced by formoterol and salmeterol,” they report.
Commenting on these findings, Dr. Lipworth noted that “as combination inhalers are being used more and more as first line therapy, prescribers need to be aware that the acute rescue response to salbutamol may be blunted with delayed recovery in the setting of acute asthma.”
“Moreover, as the blunting is not influenced by the patient’s genotype, this is going to be a problem in all patients -- not just restricted to certain patients,” he added.
Source: Thorax 2004;59:662-667. [ Google search on this article ]
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