[Drug treatment in the elderly: special aspects of diuretics (author's transl)].

Age-dependent changes in the pharmacokinetics of two diuretics, spironolactone and triamterene, were investigated in 20 geriatric patients with multiple diseases. Average plasma concentrations of canrenone (both determined by High-Performance-Liquid-Chromatography (HPLC) and a fluorimetric method) were significantly higher in geriatric patients compared with a younger control group of healthy volunteers (p less than 0,002). There was also a significant positive correlation between age (of the geriatric patients) and the area under the plasma concentration curve of canrenone. Plasma concentrations of canrenone (measured by HPLC after 120 hours) were closely correlated with number of red cells in the geriatric patients (p less than 0,01). Maximum plasma concentrations of triamterene and its pharmacologically active phase-II-metabolite were clearly higher in the geriatric patients when compared with a younger control group of healthy volunteers. Maximum plasma concentrations of the phase-II-metabolite were inversely correlated with diastolic blood pressure (p less than 0,01). Plasma levels of triamterene and its phase-II-metabolite in the older patients seem to be influenced not only renal perfusion pressure but also by uric acid levels.