The combination of two HIV drugs can be risky for heart, warns the Food and Drug Administration on Tuesday.

The agency mentioned that Roche's Invirase and Abbott Laboratories' Norvir can have an effect on the electrical activity of the heart when mutually used. Changes to the heart's electrical activity can setback the signals that trigger heart beats. Irregular heart rhythms, leading to lightheadedness, fainting, and even death can be the result of the combination.

Without talking to the doctor, patients should not stop taking Invirase as the review is ongoing, said the agency. Invirase was approved in 1995. It is marketed by Genentech, which is the biotech unit of Swiss drug maker Roche. To control HIV in adults Invirase is combined with Norvir and other anti-viral drugs.

To boost the level of Invirase in the body, Norvir is given at a low dose.

"The safety of patients is of the utmost importance to Genentech, and we continue to monitor and report to FDA adverse event reports from patients and physicians", said Tara Cooper in a statement.

A spokeswoman for Abbott said the language on heart rhythm risks already emerges in Norvir's labeling. HIV attacks the body's immune system, which ultimately causes AIDS.