Coadministration has not been studied. Gepotidacin is mainly metabolized by CYP3A4. Efavirenz is metabolized by CYP2B6 and CYP3A4. Gepotidacin does not affect CYP2B6 and is a weak inhibitor of CYP3A4, but is not expected to have a clinically significant effect on efavirenz. Efavirenz is a moderate inducer of CYP3A4 and may decrease gepotidacin exposure. A PBPK model predicted efavirenz to decrease gepotidacin AUC and Cmax by 49% and 34%. The product label for gepotidacin indicates that gepotidacin can be used with moderate CYP3A4 inducers for the treatment of uncomplicated urinary tract infections. However, when used for the treatment of uncomplicated urogenital gonorrhoea, coadministration of gepotidacin with moderate CYP3A4 inducers should be avoided. Gepotidacin 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.