In a retrospective study a total of 44 ambulatory examinations were made before enalapril was administered to 13 patients with essential hypertension and 52 ambulatory examinations during enalapril treatment of these patients. All patients were followed up on a long-term basis: 1. without enalapril treatment (2-24 months), 2. during enalapril treatment (4-24 months). For both investigation periods arithmetic means of plasma creatinine were calculated. The length of the investigation period was intentionally used as the sole criterium for inclusion in the group of patients. In nine patients during treatment the serum creatinine levels rose. The authors found a close positive correlation between the rise of plasma creatinine levels and the patients' age (correlation coefficient r = 0.59, n = 13, p < or = 0.02). Between the rise of creatinine (dependent variable) and independent variables (daily enalapril dose, initial creatinine blood level, the drop of the median arterial pressure during enalapril treatment) no close relationships were found. The rise of creatinine during enalapril treatment can be explained by a drop of the filtration pressure in the glomeruli during dilatation of the vas efferens. This drop of the filtration pressure was manifested by a slight increase of plasma creatinine only in patients with a drop of the renal perfusion (haemodynamic) reserve, i.e. in more advanced age groups.

Keywords: Aged; Aged, 80 and over; Angiotensin-Converting Enzyme Inhibitors /therapeutic use/; Creatinine /blood/; Enalapril /therapeutic use/; Female; Humans; Hypertension /blood/; Male; Middle Aged; Retrospective Studies