FDA on Thursday is expected to issue an advisory that urges physicians to conduct genetic testing before prescribing GlaxoSmithKline's antiretroviral drug abacavir to reduce allergic reactions in people taking the drug, the New York Times reports. The recommendation to conduct genetic screenings will be included in a black box warning on the drug's label.

HIV-positive people who have a certain variation in an immune system gene should not take abacavir because they have a higher risk of a severe allergic reaction to the drug, according to FDA. A GSK-sponsored study, published in the New England Journal of Medicine in February, found that genetic screening prior to prescribing abacavir could reduce the incidence of suspected hypersensitivity reactions from 7.8% to 3.4%. Symptoms of the reaction include fever, rash, nausea and breathing difficulties. Based on the data, it was estimated that about 61% of people with the genetic variant could experience a severe allergic reaction to abacavir, compared with 4% of people without the variant.

In addition, abacavir's revised label will mention a study that found an increased incidence of heart attacks among people taking the drug, the Times reports. The label also will mention that GSK conducted its own review by pooling the results of numerous clinical trials and found no increased risk of heart attack. The new label will say that although the data on the increased risk of heart attack is "inconclusive," doctors still should be cautious in prescribing the drug (Pollack, New York Times, 7/24).