Magazine article Drug Topics

Letters

Magazine article Drug Topics

Letters

Article excerpt

Salmeterol and the QT syndrome

Regarding the article on the QT syndrome in the Jan. 15 issue of Drug Topics, I feel compelled to submit a clarification based on the weight of evidence regarding the effect of the bronchodilator salmeterol (Serevent) on the QTc interval. Numerous large, well-controlled clinical trials indicate that the incidence of clinically significant ECG abnormalities and dysrhythmias was similar among patients treated with salmeterol, other asthma/COPD therapies, and placebo. And such clinically significant changes in ECGs occur infrequently.

When given in clinically approved doses for asthma, salmeterol has not been shown to prolong the QTc interval compared with placebo in children ages six to 13 and with albuterol and placebo in patients age 12 and above. At clinically approved doses, ECG data from two COPD studies investigating Serevent Diskus and from two COPD studies involving Serevent Inhalation Aerosol report no evidence for a prolonged QTc interval (change from baseline) with salmeterol compared with placebo and other therapies (i.e., Flovent, Atrovent, Advair) (data not yet published). Furthermore, an extensive prescription event-- monitoring trial in a UK cohort of 35,799 patients (15,407 of whom were on salmeterol) indicated that salmeterol was not associated with an increased risk of non-- fatal cardiac failure or ischemic heart disease.

While the class of beta^sub 2^ adrenergic agonists has a dose-related potential to induce changes in QTc interval (flattened T wave, prolongation of QTc interval, and ST segment depression of unknown clinical significance), this effect tends to occur at doses much higher than those used clinically and to be reported with the more nonselective agents.

Beta^sub 2^-adrenergic agonists are intended to cause bronchodilation clinically through their action on beta^sub 2^-adrenergic receptors that are prominent in cardiac tissue. Salmeterol is a highly selective beta^sub 1^-- adrenergic receptor that is prominent in cardiac tissue. Salmeterol is a highly selective beta^sub 2^-adrenergic agonist with a beta^sub 2^:beta^sub 1^ selective ratio 85,000:1. This compares favorably with other agents within the class, particularly fuller agonists like fenoterol and formoterol, so the potential to induce cardiovascular side effects is reduced with salmeterol. Like all sympathomimetic amines, salmeterol should be used with caution in patients with cardiovascular disorders, as they may experience cardiovascular manifestations like an increase in heart rate or blood pressure, and the drug may need to be discontinued. …

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