By Lisa Richwine

Reuters 6 Jan. '01

Washington - Pregnant women may face a higher risk of a potentially fatal side effect from an HIV-fighting drug combination than other patients, the US government and Bristol-Myers Squibb Co warned on Friday.

Two drugs, Zerit and Videx, can cause lactic acidosis, an acid buildup that can be deadly in rare cases.

The drugs' labels had included strong warnings that lactic acidosis could occur in any patient, but new evidence showed pregnant women have a greater chance of developing the condition, the Food and Drug Administration (FDA) said.

The FDA and Bristol-Myers in New York said they had received "several" reports of lactic acidosis among pregnant women, including three deaths.

Both advised pregnant women and their doctors to consider Zerit and Videx only when the benefits outweighed the risks, and, if they did use them, to watch for signs of the side effect such as abdominal pain, nausea and vomiting.

Lactic acidosis may be reversed if doctors stop treatment with the drugs.

"We've amended the label to emphasise caution" in treating pregnant women, Bristol-Myers spokesperson John Kouten said.

The company immediately notified the FDA when it learned about the risks for pregnant women, Kouten added, and the company was sending letters to about 50 000 health care providers to explain the warning.

Kouten stressed that the the drugs still were considered safe and effective and that tens of thousand of patients with HIV, the virus that causes Aids, had taken the combination.

Only a small number of those patients were pregnant, he said.

"We don't want patients who are on the therapy to be alarmed. Patients who are taking this already know that lactic acidosis is a side effect to look for," Kouten said.

Lactic acidosis occurs when the body's cells are unable to convert food into usable energy. As a result, excess acid accumulates in the body, and vital organs such as the liver or pancreas can be damaged.

Worldwide sales in 1999 were $605-million (about R4-billion) for Zerit and $205-million for Videx.