Adult HTN Initially 40 mg bid increasing according to response every 3-7 day, max dose: 480-640 mg/day (if used w/ diuretics & hydralazine, max dose: 320 mg/day). Angina & migraine Initially 10-20 mg tid-qid increasing according to response, max dose: 120-240 mg/day. Cardiac arrhythmia, thyrotoxicosis 10-40 mg tid-qid. Prevention of myocardial reinfarction 180-240 mg tid-qid in divided doses. Pheochromocytoma 20 mg tid or 40 mg tid-qid w/ an α-adrenergic blocker 3 days pre-op. Childn Initially 0.5-1 mg/kg/day tid-qid in divided doses. Maintenance: 2-4 mg/kg/day bid in divided doses.