GlaxoSmithKline on Friday said it had come to an agreement with the US Food and Drug Administration to include a warning of asthma death in the labeling for its long-acting beta2-agonists Serevent (salmeterol) and Advair (salmeterol/fluticasone).

The news follows data from a large placebo-controlled US study that compared the safety of Serevent or placebo against background asthma therapy and found an increase in asthma-related deaths in patients receiving the GSK drug (13 deaths out of 13,176 patients treated for 28 weeks on salmeterol versus 3 deaths out of 13,179 patients on placebo).

The new labeling will point doctors away from prescribing dual therapy including Serevent/Advair as a first line of attack, with the labeling stating the drugs “should only be used as additional therapy for patients not adequately controlled on other asthma controller medications [and] whose disease severity clearly warrants initiation of treatment with two maintenance therapies.” A medication guide has also been designed to raise patient awareness on the safety and proper use of Serevent and Advair.

GSK stresses that it still remains confident in the safety profile of Serevent and Advair when “used appropriately.” And the shift from first to second or even third line therapy appears unlikely to have much impact on Advair’s sales. Despite the furore over the clinical trial data, an initial label revision in 2004 highlighting an increased incidence of asthma death amongst salmeterol receivers, and the FDA’s decision last year to strengthen the warning, sales of Advair jumped 22% over the year to £3 billion.