Renal concentrating capacity in long-term lithium treatment and after withdrawal of lithium.

The urinary concentrating capacity was estimated with the DDAVP test in 87 patients receiving lithium therapy, which was discontinued in all patients. The test was repeated three and eight weeks after withdrawal of lithium in 75 patients and one year after withdrawal in 27 patients. Of the 87 patients, 52 were also treated with neuroleptics, which treatment was continued throughout the study. Two control groups, consisting of 30 patients receiving only neuroleptics and 30 healthy subjects, were studied on one occasion with the DDAVP test. Lithium-treated patients had significantly lower concentrating capacity and higher serum creatinine than healthy subjects at all examinations. Small but statistically significant correlations were found between urinary osmolality and total dose of lithium, between urinary osmolality and duration of lithium treatment, between the highest serum lithium concentration recorded and urinary osmolality after withdrawal of lithium and between the daily dose of lithium and urinary osmolality, while patients were still on lithium. The concentrating capacity improved significantly during the first two months after withdrawal of lithium, but not later. One year after withdrawal of lithium, 17 of 27 patients still had a concentrating capacity below 800 mOsm/kg. Patients receiving lithium and neuroleptics had lower concentrating capacity than patients treated with lithium alone, and patients treated with neuroleptics alone had lower concentrating capacity than healthy subjects.