50 mL (10 mL min.) aliquot of 24-hour urine. Collect urine with appropriate volume of 50% HCl to maintain pH between 1-2. Do not use concentrated HCl. Record 24 hour volume on test request form and urine container. Ship refrigerated or frozen. Patient should strictly avoid Alpha-one blockers, Aminophylline, Amphetamines, Ampicillin, Beta-blockers, Ephedrine, Imipramine, Methyldopa, MAO inhibitors, Nicotine, Phenacetin, Phenothiazine, Theophylline, Vasodilators, Aspirin, PAS, Alpha-2 agonists, Bromocriptine, Calcium channel blockers ( long term use), Clofibrate, Propranolol, Penicillin, Reserpine, Thyroxine, Alpha-methyldopa, Isoproterenol, Labetalol, Mandelamine, Paracetamol, Cimetidine, Metoclopramide, vigorous exercise, alcoholic beverages, tea/coffee and tobacco at least 72 hours before and during specimen collection.