HomeRifamycins are the only anti-tuberculous agents to exert clinically important interactions with antiretroviral drugs (see Table 1). Rifabutin is associated with weaker enzyme induction and thus has less potential for serious drug-drug interactions than either rifapentine or rifampin. However, there is less published clinical experience with rifabutin in the treatment of people with both HIV and TB, and rifampin is usually preferred in this population.23,38
Since rifamycin-based TB treatment is strongly recommended in people with HIV and TB (see recommendation in section 2.1), these drug-drug interactions substantially limit the number of compatible ART regimens available. Current recommendations from the World Health Organization (WHO) for people newly diagnosed with HIV and on treatment for TB is dose-adjusted dolutegravir plus 2 nucleoside analogues. An acceptable alternative is efavirenz plus 2 nucleoside analogues (see Table 1 for dosing for both regimens).38
The management of drug-drug interactions between ART and the rifamycin class is an area of active research and recommendations change frequently. Consultation with an experienced pharmacist and a regularly updated clinical drug-interaction resource is prudent (see section 13 on drug-drug interactions).
It is crucial that, while on TB treatment, ongoing monitoring of antiretroviral efficacy is performed. ART efficacy can be compromised in people with HIV and TB co-infection because of drug-drug interactions, reduced adherence related to increased pill burden or overlapping toxicity. Thus, we strongly advise close monitoring of plasma HIV ribonucleic acid (RNA) in people on TB treatment. Monthly testing is recommended until plasma viral load is no longer detectable and then, at minimum, quarterly testing while on TB treatment.
In patients with a suboptimal virologic response to ART in whom an interaction or decreased absorption is a possible explanation, measurement of serum antiretroviral concentrations should be considered, although clinical evidence to support this strategy is lacking. Adherence to ART should also be optimized and antiviral resistance excluded.
Good practice statement
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Close monitoring of plasma human immunodeficiency virus (HIV) RNA in people on treatment for both TB and HIV is suggested with monthly measurements until plasma HIV RNA is no longer detected, followed by quarterly testing during the course of TB treatment.
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