Glomerular filtration rate during lithium therapy. A longitudinal study.

In order to investigate the side effect of lithium on renal function the glomerular filtration rate (GFR) was measured before (to) and after a mean of 16.5 months (t1) (range 12-25 months) lithium treatment in 13 consecutive patients aged 32-67 years (mean age 46 years). The patients had a normal renal function before the treatment was started; none of them had previously been treated with lithium. During treatment GFR (ml/min) fell from 101.9 to 98.3 which was not significant. However, standard-GFR (ml/min/1.73 m2) fell from 88.4 to 84.8 (P less than 0.05) mainly due to a significant rise in body weight and estimated surface area during treatment. No significant changes appeared in plasma creatinine. It is concluded that lithium therapy for a mean of 16.5 months does not affect the glomerular filtration rate; but considerably longer observations of GFR during lithium therapy should be done by means of a reliable GFR measurement method.