A key anti-HIV/AIDS drug distributed in Africa causes drug resistance in pregnant women, but only if they ignore doctors’ orders on how to take the pills, medical officials said on Monday.

The drug, nevirapine, is distributed as part of President Bush’s high-profile bid to fight the spread of the disease in Africa and help AIDS sufferers.

The announcement confirms in part media reports that suggested single doses of nevirapine, used to stop HIV-positive mothers passing the virus to their babies, could result in resistance to future treatment.

Uganda’s Makerere University Medical School and two U.S. institutions issued a joint statement on Monday in a bid “to clarify the scientific facts, based on the full body of evidence.”

They were the Johns Hopkins University School of Medicine and the U.S.-based Elisabeth Glaser Pediatric AIDS Foundation.

The statement did not comment on allegations that trials of the drug at Kampala’s Mulago Hospital failed to meet international standards and that the U.S. rolled-out nevirapine across Africa despite concerns over the tests.

Nevirapine is manufactured by German firm Boehringer Ingelheim.

“It is true that resistance has been shown to occur in those receiving short-course nevirapine,” said the joint statement in the Ugandan capital.

It was issued by Laura A. Guay MD, associate professor of pathology and pediatrics at Johns Hopkins University, and Dr Phillipa Musoke, head of pediatrics at Makerere University Medical School.

“The problem of drug resistance has partly been as a result of violations in prescription rules. However, to date, there is no evidence of negative clinical outcomes as a result of subsequent antiretroviral therapy,” the statement said.

South Africa’s ruling African National Congress (ANC) on Friday accused U.S. health officials of treating Africans like guinea pigs by agreeing to distribute nevirapine despite concerns over the trials.

The ANC repeated media reports that the U.S. National Institutes of Health (NIH) and the U.S. Food and Drug Administration halted a U.S. audit on the drug because of fears over the Ugandan tests.

The reports said the NIH failed to pass those concerns on to the White House before the roll-out of nevirapine across Africa.

Officials at NIH have said there was no need to inform the White House because the drug’s effectiveness was not at issue, only that there were “observed procedural deficiencies” in the Ugandan trials.

“NIH officials did not directly inform the White House of these procedural problems identified in early 2002 because they had no bearing on the safety and efficacy of single-dose nevirapine used to prevent mother-to-infant transmission of HIV,” said a spokesman for the U.S. National Institute for Allergy and Infectious Diseases, a unit of NIH.

The U.S.-based Centers for Disease Control and Prevention will now run tests to examine the long-term effects of taking a single dose of nevirapine on women’s later response to a range of antiretroviral treatments, the statement said.