Coadministration of bedaquiline (400 mg single dose) and efavirenz (600 mg once daily) to 33 HIV/TB-negative subjects decreased bedaquiline AUC by 18% and had no effect on Cmax. Efavirenz pharmacokinetics were similar to historical data from HIV-infected subjects. A reduction in bedaquiline exposure may result in loss of activity and coadministration is not recommended. There are no clinical data on the safety and efficacy of bedaquiline when co-administered with antiretroviral agents. Bedaquiline has a possible risk of QT prolongation and/or TdP on the CredibleMeds.org website. Efavirenz was shown to prolong the QT interval above the regulatory threshold of concern in homozygous carriers of the CYP2B6*6/*6 allele (i.e. 516T variant in the gene encoding CYP2B6). The European product label for efavirenz contraindicates coadministration with a drug with a known risk of Torsade de Pointes whereas the American product label for efavirenz recommends that alternatives should be considered. As the potential risk of a QT interval prolongation relates specifically to homozygous carriers of CYP2B6*6/*6 and given the accumulated years of safety data with efavirenz and such drugs, the contraindication is not reflected in the colour coding of this interaction summary.