Impaired absorption w/ antacids eg, Mg or Al hydroxide, didanosine, sucralfate, minerals & multivitamins. Increased risk of ventricular arrhythmias notably Torsades de pointes w/ other drugs known to prolong QT interval eg, anti-arrhythmics class IA eg, quinidine, hydroquinidine, disopyramide or anti-arrhythmics class III eg, amiodarone, sotalol, dofetilide, ibutilide, neuroleptics eg, phenothiazines, pimozide, sertindole, haloperidol, sultopride, TCAs, certain antimicrobials eg, sparfloxacin, erythromycin IV, bepridil, diphemanil. Drug induced-bradycardia or hypokalemia or induced-QT prolongation eg, neuroleptic, certain anti-infective agents eg, some antimalarials, azole antimycotics, macrolides, certain antihistaminics eg, terfenadine, astemizole, cisapride.