Increased plasma levels w/ CYP3A4 inhibitors (potent CYP3A4 inhibitors eg, PIs, systemic azole antifungals, erythromycin, clarithromycin, telithromycin; moderate CYP3A4 inhibitors eg, diltiazem, verapamil & some macrolides). Increased risk of occurrence of QT-interval prolongation w/ QTc-prolonging medicinal products eg, disopyramide, hydroquinidine, quinidine, amiodarone, dofetilide, dronedarone, ibutilide, sotalol, haloperidol, pimozide, sertindole, citalopram, escitalopram, erythromycin, levofloxacin, moxifloxacin, spiramycin, pentamidine, halofantrine, lumefantrine, cisapride, dolasetron, prucalopride, mequitazine, mizolastine, toremifene, vandetanib, vincamine, bepridil, diphemanil, methadone, apomorphine. Caution w/ bradycardia- & hypokalaemia-inducing drugs, azithromycin, roxithromycin.