HIV treatment 'affected by TB drug'. 04/08/08

August 4, 2008

A drug used to fight TB also hampers the effectiveness of an HIV treatment widely used in Africa, the world's worst Aids-hit region, a study says.

The antibiotic rifampicin reduces concentrations in the blood of nevirapine, a low-cost agent that is part of the frontline therapy against HIV in poor countries, especially Africa.

The study was presented on Sunday ahead of the start of the 17th International Aids Conference, which runs in Mexico City until Friday.

The evidence comes from a study, which unfolded in South Africa between 2001 and 2006, among 2 035 people who began their treatment with efavirenz, 1 074 of whom had TB and 1 935 others who initiated their treatment with nevaripine, of whom 209 also had TB.

In the nevaripine group, 16,3 percent of patients with TB were nearly twice as likely to have elevated levels of HIV in their blood at a six-month follow-up check-up, compared to only 8,3 percent among those without TB.

They were also twice as likely to develop treatment failure faster than patients who did not have TB.

However, a large majority - 80 percent - of TB patients using nevirapine also succeeded in suppressing the virus at an 18-month check-up.

The findings are of high importance for sub-Saharan Africa, which is home to two-thirds of the 33-million people infected by HIV.

Globally, an estimated one-third of people living with HIV are co-infected with TB.

For reasons that are poorly understood, co-infection can cause a lightning-fast decline in health, especially if the TB strain is resistant to frontline antibiotics.

The death rate among cases of co-infection is five times higher than for TB alone.

The Journal of the American Medical Association study, led by Andrew Boulle, of the University of Cape Town, said it was unclear why rifampicin had such an impact on nevaripine.

One possible reason could be a shared toxicity. Another reason could be a drug interaction, caused by rifampicin, when the patient started to receive early doses of the antiretroviral.

Anti-HIV drugs suppress the virus but do not eradicate it completely. If the drugs are halted, the Aids rebounds. - Sapa-AFP.