Drug maker Novartis AG on February 20 alerted doctors to the possibility of a potentially fatal heart problem in patients treated with the company's schizophrenia drug Clozaril.

In a letter to physicians, Switzerland-based Novartis said post-marketing data from four countries revealed 82 reports of an inflammation of the heart lining known as myocarditis in patients treated with Clozaril.

The company added a caution about myocarditis to the "black box" warning on the label for the prescription drug, known generically as clozapine.

The black box section, the strongest type of warning for a prescription drug, was moved to the beginning of the Clozaril label, Novartis said. The boxed warnings also include previous cautions about the possibility of serious side effects such as seizures and a drop in white blood cells in patients treated with Clozaril.

Surveillance of the drug since it hit the market has revealed 30 reports of myocarditis, 17 of them fatal in US patients treated with Clozaril, and 14 additional patients died overseas.

Over half of the deaths occurred within the first month of Clozaril treatment, according to data on the updated label.

Doctors should consider the possibility of myocarditis in Clozaril patients with unexplained fatigue, fever or malaise, the letter said.

The company worked with the Food and Drug Administration (FDA) to develop the wording for the warning, Novartis spokesman Harry Rohme said.

Reuters February 21, 2002