Visits 3 - 6 (follow-up observation, months 6, 12, 18 and 24): The current medication of the patient will be recorded (with especial emphasis on the following concomitant medications: ACE inhibitors, AngII blockers, statins, erythropoietin, beta-blockers). Questions will be asked about newly developed diseases with special attention to the occurrence of diabetes mellitus, coronary heart disease, stroke (including transitory ischaemic attacks [TIA] and prolonged reversible ischaemic neurological deficits [PRIND]) and peripheral arterial occlusive disease. The blood pressure, pulse rate and body mass index will be recorded. The study medication will be counted. New supplies of study medication for 28 weeks will be issued. Questions will be asked about side-effects. The patient will be asked about current symptoms. Laboratory values will be recorded in the course of the routine monitoring of the patient (abbreviated routine laboratory: hemoglobin, leukocyte count, platelet count, calcium, calcium x phosphate product, urea, serum creatinine, total protein).