Increased risk of torsades de pointes w/ class Ia (eg, quinidine, procainamide, disopyramide) & III (eg, sotalol, bretylium) anti-arrhythmics; IV erythromycin, co-trimoxazole or pentamidine inj; anti-psychotics eg, chlorpromazine, thioridazine, fluphenazine, pimozide, haloperidol, amisulpride, sertindole; lithium & TCAs eg, doxepin, maprotiline, amitriptyline; antihistamines eg, terfenadine, astemizole, mizolastine; anti-malarials eg, quinine, mefloquine, chloroquine, halofantrine; moxifloxacin; QT-interval prolonging drugs (eg, clarithromycin). Avoid concomitant use w/ fluoroquinolones. Potentiated negative chronotropic properties & conduction slowing effects may occur w/ β-blockers & Ca channel inhibitors eg, diltiazem, verapamil. Combined therapy w/ stimulant laxatives is not recommended. May cause hypokalaemia &/or hypomagnesaemia w/ diuretics, systemic corticosteroids, tetracosactide, IV amphotericin. Potential severe complications w/ general anaesth & high dose O2
therapy. May inhibit CYP1A1, CYP1A2, CYP3A4, CYP2C9, CYP2D6 & P-gp & increase exposure to their substrates. Increased plasma conc of digoxin, oral anticoagulants (eg, warfarin), phenytoin. Risk of bleeding w/ dabigatran. May increase plasma levels of ciclosporin, drugs metabolized by CYP3A4 (eg, lidocaine, tacrolimus, sildenafil, fentanyl, midazolam, triazolam, dihydroergotamine, ergotamine, colchicine), flecainide. May potentiate pharmacological effects of fentanyl. Increased risk of muscular toxicity eg, rhabdomyolysis w/ statins metabolized by CYP3A4 eg, simvastatin, atorvastatin, lovastatin. CYP3A4 & CYP2C8 inhibitors may inhibit metabolism & increase exposure. May increase plasma conc w/ grapefruit juice. Potential serious symptomatic bradycardia w/ sofosbuvir in combination w/ another HCV direct-acting antiviral eg, daclatasvir, simeprevir, ledipasvir.