Longitudinal evaluation of glomerular filtration rate during long-term lithium therapy.
Lithium produces many renal effects, but the important question of whether or not it causes chronic interstitial nephritis with consequent reduced glomerular filtration rate (GFR) remains unanswered. The several studies carried out in this area have been cross-sectional and, therefore, have not contained prospective information regarding creatinine clearance. The present study provides data from seven patients in whom creatinine clearances were obtained bracketing an average span of 7.5 years of continuous lithium therapy. Over this time, there was no significant change either in mean serum creatinine concentration or in average creatinine clearance (first determination: 1.1 +/- 0.1 [SE] mg/dL, 99 +/- 8 mL/min/1.73 m2; second determination 1.0 +/- 0.1, 105 +/- 4, respectively). The data, thus, support preservation of GFR during long-term lithium therapy.