Long-term lithium treatment and renal functions. A prospective study.

Renal functions were examined in 53 patients before the start of long-term lithium treatment (I) and then after 4 months (II) and 12 months (III) on lithium treatment. The tubular function was studied by means of the DDAVP (Minirin) test and the glomerular filtration rate was measured by creatinine clearance. The mean maximum urine osmolality (+/- SE) on the first occasion (I) was 800 +/- 20 mosm/kg H2O, 702 +/- 20 on the second (II), and on the third (III) 723 +/- 17 mosm/kg H2O. The mean creatinine clearance before the start of lithium treatment (I) was 128 +/- 5 ml/min, after 4 months (II) 106 +/- 4 and after 12 months (III) 114 +/- 5 ml/min. The results of the present study suggest that lithium treatment with serum levels of approximately 0.6 mmol/l causes a decrease in renal concentrating ability and the glomerular filtration rate in the early stages after the start of therapy. This decrease in the renal functions does not seem to progress during the first year of lithium treatment.