September 2, 2008

Norvir and Heart Conduction Disturbances

People taking 400 mg or more of Norvir (ritonavir) twice-daily may have delayed conduction of electrical charges in their hearts, according to a notice from the U.S. Food and Drug Administration (FDA) detailing revisions to Norvir’s prescribing information.

For the heart to beat properly, an electrical charge flowing between the organ’s four chambers must travel at the right speed. This is determined by using an electrocardiogram (ECG) to measure what are known as the PR and QT intervals. Both can be altered by certain medications as well as by underlying disease or damage to the heart.

The FDA is now alerting health care providers and people living with HIV about two new studies that examined the affect of 400 mg of Norvir, taken twice-daily, on the PR and QT intervals in HIV-negative patients. Compared with a placebo, researchers found that Norvir caused a delay in both the PR and QT intervals.

“Norvir should be used with caution in patients with underlying structural heart disease, preexisting conduction system abnormalities, ischemic heart disease [and] cardiomyopathies, as these patients may be at increased risk for developing cardiac conduction abnormalities,” the prescribing information now says.

The prescribing information also urges health care providers to use caution when prescribing Norvir with other medications that can cause heart conduction problems.

Search: heart conduction, Norvir, ritonavir, FDA, electrocardiogram, ECG, PR interval, QT interval

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