Obtain ECG prior to initiation of treatment & at least 2, 12 & 24 wk after starting treatment; serum K, Ca, Mg at baseline, correct if abnormal. Monitor electrolytes if QT prolongation is detected; symptoms (eg, fatigue, anorexia, nausea, jaundice, dark urine, liver tenderness & hepatomegaly) & laboratory tests (ALT, AST, alkaline phosphatase & bilirubin) at baseline, mthly while on treatment & as needed. Patients w/ arrhythmias or recent MI; risk for QT prolongation in patients in concomitant use w/ drugs prolonging QT (eg, fluoroquinolones, macrolides, antimycobacterials & clofazimine); history of Torsades de Pointes, congenital long QT syndrome, ongoing hypothyroidism or bradyarrhythmias, uncompensated heart failure, serum Ca, Mg, or K levels below the lower limits of normal. Discontinue if clinically significant ventricular arrhythmia & a QTcF interval of >500 ms; aminotransferase elevations are accompanied by total bilirubin elevations >2 x ULN, >8 x ULN, >5 x ULN occur. Avoid concomitant use w/ alcohol & other hepatotoxic drugs especially in patients w/ impaired hepatic function; strong [rifamycins (ie, rifampin, rifapentine, & rifabutin)] & moderate (eg, efavirenz) CYP3A4 inducers; strong CYP3A4 inhibitors for >14 consecutive days. Severe hepatic or renal impairment or end-stage renal disease requiring hemodialysis or peritoneal dialysis. Pregnancy & lactation. Ped patients. Elderly >65 yr.