The data suggest that together the two drugs may affect the electrical activity of the heart, known as prolonged QT or PR intervals. A prolonged QT interval can increase the risk for a serious abnormal rhythm called torsades de pointes. A prolonged PR interval can cause the electrical signal responsible for generating a heart beat to slow or even stop, known as heart block.
FDA's analysis of these data is ongoing. The agency will update the public as soon as this review is complete. However, healthcare professionals should be aware of this potential risk for changes to the electrical activity of the heart. Invirase and Norvir should not be used in patients already taking medications known to cause QT interval prolongation such as Class IA (such as quinidine,) or Class III (such as amiodarone) antiarrhythmic drugs, or in patients with a history of QT interval prolongation.
Patients should not stop taking their prescribed antiviral medications. Patients who are concerned about possible risks associated with using Invirase and Norvir should talk to their healthcare professional.
Healthcare professionals and patients are encouraged to report adverse events or side effects related to the use of these products to the FDA's MedWatch Safety Information and Adverse Event Reporting Program:
- Online: www.fda.gov/MedWatch/report.htm
- Phone: 1-800-332-1088
- Mail: return the postage-paid FDA form 3500, which may be downloaded from the MedWatch "Download Forms" page, to address on the pre-addressed form
- Fax: 1-800-FDA-0178