Health officials and activists fighting AIDS in South Africa on Thursday stood by a key drug, nevirapine, the U.S. Food and Drug Administration (FDA) warned a day earlier could cause deadly liver damage.

The FDA warning is particularly sensitive in South Africa, which has the world’s highest caseload of HIV and AIDS with some 5 million people infected out of a population of 45 million. Activists reckon 600 people die daily from HIV/AIDS.

“Any fundamental change in the policy (to use nevirapine) will be determined by compelling evidence scientifically supported by the WHO (World Health Organization),” said Solly Mabotha, a spokesperson at the Department of Health, which oversees the anti-retroviral (ARV) treatment program.

Mabotha said the department was working with research institutions to fully understand nevirapine’s adverse effects.

Nevirapine is the generic name for Viramune, made by Germany’s Boehringer Ingelheim, and is distributed in African countries as part of President Bush’s effort to fight the spread of AIDS.

It is one of the medicines used in drug cocktails that can suppress HIV and keep patients healthy longer, and is used briefly to treat HIV-positive pregnant women so that they don’t pass the virus on to their newborns.

South Africa’s ruling African National Congress sparked a controversy last month after it accused U.S. officials of conspiring with Boehringer to hide the side effects of nevirapine. U.S. health officials disputed the charge.

In its warning issued on Wednesday, the FDA asked doctors to weigh benefits and risks before prescribing nevirapine.

Boehringer said the FDA warning would not stop it from offering Viramune free of charge to prevent mother-to-child transmission of HIV in poor countries.

“Doctors specializing in HIV were aware of liver toxicity issues and we do not expect any major change in treatment including nevirapine,” a company spokeswoman said.

Activists said they had little choice for now.

“As consumers we cannot say we are going to stop until the body that controls nevirapine in the country says so, by which time there may be a better alternative,” said Thanduxolo Doro, a spokesman for South Africa’s National Association of People with AIDS (NAPWA).

Zackie Achmat, who heads South Africa’s leading AIDS lobby, the Treatment Action Campaign, and is himself on antiretroviral treatment, said the FDA’s findings were not new. All ARVs were known to have side effects, including liver damage, he said.