Lithium and impairment of renal concentrating ability.

In 19 patients on lithium maintenance therapy, impairment of renal concentrating ability was found to correlate with daily lithium dose. The correlation between dose and impaired renal concentrating ability was strongest for patients on regular lithium preparations and not significant for patients on a slow release preparation. In 2 patients with severe polyuria, renal concentrating ability increased markedly with thiazide treatment. No relationship between lithium dosing parameters and other side effects was found. These results emphasize the importance of dose and type of preparation of lithium in the production of renal side effects.