Health Canada Updates Label for Zithromax

Ottawa, CanadaHealth Canada has announced it is updating the Zithromax side effects label to warn about a risk of cardiovascular events. The updated warning does not involve the reported risk of Zithromax Stevens Johnson Syndrome, an allergic reaction that occurs in response to some medications. In 2012, the maker of Zithromax received a warning letter from the US Food and Drug Administration (FDA) about its marketing of a Zithromax product - Zmax - concerned that the company had downplayed the risks of Stevens Johnson Syndrome.

CBC News (5/17/13) reports that Health Canada has announced both Zithromax and Zmax SR (both known generically as azithromycin) will have updated warnings to include the risk of possibly fatal cardiac problems. Health Canada noted that a study found a small increase in the risk of fatal heart events in patients who used azithromycin when compared to patients who took amoxicillin or who took no antibiotics.

The updated warning in Canada follows a similar warning in the US that Zithromax was associated with changes in the electrical activity of the patient’s heart. Those changes could result in a life-threatening heart rhythm.

A Danish study published in the New England Journal of Medicine (5/2/13), however, found no increase in the risk of death from heart problems in patients who used azithromycin compared with patients who used penicillin. The risk of death was greatly increased when patients who took azithromycin were compared with patients who took no antibiotic.

Azithromycin is an antibiotic that is used to treat bacterial infections, including pneumonia, urinary tract infections and skin infections. It has been linked in one study (found at the National Center for Biotechnology Information; 2006) to two cases of Stevens Johnson Syndrome, including a 62-year-old woman who took azithromycin for an upper respiratory tract infection and developed Stevens Johnson Syndrome.

Stevens Johnson Syndrome is a potentially fatal allergic reaction to some medications, which can include Zithromax. Patients often develop a fever, headache and sore throat, followed by skin lesions and blisters. The condition can develop far enough that the patient’s skin sloughs off and his or her eyesight can be affected. Patients who survive their ordeal can have permanent injury, including scarring, sensitivity to light and respiratory problems.

In June 2012, the FDA sent a letter to Pfizer, maker of Zithromax, warning that the company must not downplay the risk of Stevens Johnson Syndrome in its marketing materials. Among the FDA’s concerns about the “1 Day. 1 Dose” brochure for Zmax (which is azithromycin extended-release medication) was that the brochure did not adequately address the severity of Stevens Johnson Syndrome.