NEW YORK The U.S. Food and Drug Administration said on Tuesday that HIV drugs Invirase and Norvir might lead to an abnormal heart rhythm when used in combination, according to preliminary data the agency is reviewing.
Medicines to treat HIV -- the virus that causes AIDS -- are typically given in multi-drug combinations. Norvir is sold by Abbott Laboratories, while Invirase is made by Roche Holding Ltd's Genentech unit.
When used together, the drugs may cause prolongation of the QT and PR intervals on an electrocardiogram, the FDA said. Both conditions may lead to dangerously abnormal heart rhythms.
"Preliminary findings suggest that some patients using Invirase and Norvir may be at an increased risk for heart abnormalities leading to irregular heart rhythms," the FDA said in a news release.
The heart conditions can cause lightheadedness or fainting and may lead to a life-threatening irregular heart beat known as ventricular fibrillation.
The heart risk may be increased in patients who are also using medications known to cause QT interval prolongation, the agency said. The risk may also be increased in patients who have a history of QT interval prolongation.
Genentech spokesman Terry Hurley said it had turned over to the FDA results of an Invirase study that showed the potential for QT prolongation. "Updates to the Invirase prescribing information are being submitted to FDA and will be finalized when their review is complete," he said.
Abbott spokeswoman Elizabeth Hoff said the company had added information to Norvir's label about the risk in 2008. The drug's prescribing instructions say it prolongs the PR interval in some patients.
Invirase, an antiretroviral medication approved in 1995, is commonly used in combination with Norvir and other antiretroviral medicines. Invirase is known chemically as saquinavir, while the chemical name for Norvir is ritonavir.
The FDA said it will make public its findings as soon as its review of data on the drug combination is complete.
(Reporting by Bill Berkrot and Lisa Richwine; editing by Andre Grenon and Carol Bishopric)