Increased absorption w/ food. Avoid use w/ strong CYP3A4 inducers eg, phenytoin, carbamazepine, rifampicin, rifabutin, rifapentine, phenobarb, St. John's wort. Drugs known to prolong QT interval & induce Torsade de pointes eg, class IA or III antiarrhythmics, methadone, moxifloxacin, antipsychotics. Increased prostate specific antigen levels w/ spironolactone. CYP2D6 & CYP2C8 inhibitors. CYP2D6-metabolised drugs eg, metoprolol, propranolol, desipramine, venlafaxine, haloperidol, risperidone, propafenone, flecainide, codeine, oxycodone, tramadol.