Objectives. The most frequent renal side-effect of lithium is an impairment of concentrating ability and, after 10–20 years, a chronic tubular-interstitial nephropathymay occur in some patients. Discontinuation of lithium, especially in "excellent lithium responders" (ELR), is associated with a high risk of relapse and a treatment-resistant course. The purpose of the study was to assess kidney function during a five-year follow-up in the ERL with the glomerular filtration rate (GFR) < 50 ml/min/1.73 m2.
Material and methods. Three males and one female were included. At the beginning their age was 61 ± 0.8 years and duration of lithium treatment was 27 ± 9 years. Kidney parameters (serum creatinine, GFR, and urine specific gravity) were assessed at least three times during the five-year follow-up period.
Results. The patients examined had the mean change of GFR of –2.5 ± 7.7%, serum creatinine –0.5 ± 7.3%, and urine specific gravity of 0.0025 ± 0.0041 g/ml. In three patients having the initial GRF between 47–48 ml/min/1.73 m 2 , the kidney parameters did not show significant changes and the patients continued lithium treatment as previously. The patient with the lowest GFR (32 ml/min/1.73 m 2 ) had a 14% decrease in GFR and a 10% increase in serum creatinine. The dose of lithium was decreased by one-third and he was placed under strict nephrological observation.
Conclusions. Based on the results and in the ELR with the GFR not much lower than 50 ml/min/1.73 m 2 , we suggest continuing lithium with a yearly check on kidney parameters. In the ELR with a much lower GFR, a reduction of lithium dose, and nephrological observation along with more frequent monitoring would be recommended.