Coadministration has not been studied but based on metabolism and clearance a pharmacokinetic interaction is unlikely. Ondansetron is metabolized mainly by CYP1A2 and CYP3A4 and to a lesser extent by CYP2D6. Rilpivirine at a dose of 25 mg once daily is unlikely to have a clinically relevant effect on the exposure of medicinal products metabolised by CYP enzymes. Rilpivirine has been associated with prolongation of the QTc interval at supra-therapeutic doses but these are unlikely to occur during coadministration with ondansetron. However, given the known QT prolongation risk associated with ondansetron, caution is recommended.