Anti-TB treatment lessens effect of some HIV treatments

In resource-limited countries, patients are often treated for tuberculosis at the same time that they are undergoing antiretroviral therapy (ART) for HIV. The nevirapine-based antiretroviral therapy is often used to treat HIV in the developing world due to its lower cost.

Andrew Boulle and colleagues from the University of Cape Town suggest that either shared toxicity or adverse drug interactions are driving the complications seen when ART and anti-tubercular therapy are administered together. It is known that rifampicin-based anti-tubercular therapy has an effect of reducing concentrations of both ART agents efavirenz and nevirapine in the blood plasma, but how exactly these interactions affect the viruses remains unknown.

Of the 3009 individuals in the analysis, 2035 individuals began antiretroviral therapy with efavirenz (1074 also had tuberculosis) and 1935 began antiretroviral therapy with nevirapine (209 also had tuberculosis).

At a six month follow-up, tuberculosis patients who began ART with nevirapine were found to be about two times as likely to have higher viral loads than those who began nevirapine without tuberculosis. Patients who were taking anti-TB treatment as well as nevirapine were twice as likely to experience virological failure. However, in spite of this, 80% of patients taking nevirapine and anti-TB treatment showed virological suppression after 18 months of treatment. There were no significant differences found between patients free of tuberculosis on nevirapine or rifampicin and patients starting efavirenz with and without tuberculosis treatment, or in patients developing tuberculosis while on the same ART drug.

Recently, 40% of patients starting antiretroviral treatment have also been found to have active TB.