Adolescent, Adult, Aged, Aged, 80 and over, Angiotensin Receptor Antagonists, Antihypertensive Agents, Blood Pressure, Diastole, Dizziness, Double-Blind Method, Female, Headache, Humans, Hypertension, Losartan, Male, Middle Aged, Patient Dropouts, Systole, Tetrazoles, Treatment Outcome, Valine, Valsartan