The U.S. Food and Drug Administration (FDA) just announced that preliminary data suggests that <"http://www.yourlawyer.com/practice_areas/defective_drugs">Invirase (saquinavir), in combination with Norvir (ritonavir), may have potentially important adverse effects on the heart.
When used together, the drugs may cause prolongation of the QT and PR intervals on an electrocardiogram. Prolongation of the QT interval may lead to a condition known as torsades de pointes, an abnormal heart rhythm. Prolongation of the PR interval may also lead to an abnormal heart rhythm known as heart block. With torsades de pointes or with heart block, patients may experience lightheadedness, fainting, or abnormal heart beats. In some cases, torsades de pointes may progress to a life-threatening irregular heartbeat known as ventricular fibrillation.
Review of the data is ongoing, said the FDA. Preliminary findings suggest that some patients using Invirase and Norvir may be at an increased risk for heart abnormalities leading to irregular heart rhythms. For example, the risk for torsades de pointes may be increased in patients who are also using medications known to cause a heart disturbance called QT interval prolongation. The risk may also be increased in patients who have a history of QT interval prolongation.
Patients using Invirase should talk to their health care professional about any questions or concerns they have about Invirase. Also, patients and health care professionals should report any side effects from the use of Invirase to the FDAâ€™s MedWatch program at:â€¨http://www.fda.gov/safety/MedWatch/default.htm
Invirase is an antiretroviral medication first approved in 1995 and is used in combination with Norvir and other antiretroviral medicines to treat HIV in adults. Invirase does not cure HIV infection, may not prevent people from developing HIV-related illnesses, and may not prevent people from spreading HIV to other people.
Reuters noted that, in the treatment of HIV, which is the virus that causes AIDS, medications are given in combinations. It is the combination of the drugs noted that could lead to an extended QT and PR interval; these conditions could lead to what Reuters described as â€œdangerously abnormal heart rhythms.â€
Genentech spokesman Terry Hurley said it had turned over results of an Invirase study that revealed QT prolongation potential, said Reuters. “Updates to the Invirase prescribing information are being submitted to FDA and will be finalized when their review is complete,” said Hurley, quoted Reuters.
Elizabeth Hoff, spokeswoman for Abbott said it added the risk information to Norvirâ€™s label in 2008, wrote Reuters. The drug’s prescribing instructions say it prolongs the PR interval in some patients.
The FDA said it will release its findings to the public once its review of data on the drug combination is complete.
Invirase is marketed by San Francisco-based Genentech, a subsidiary of the Roche Group. Norvir is marketed by Abbott Park, Ill.-based Abbott Laboratories.