Ibuprofen can increase serum lithium level in lithium-treated patients.

The interaction between lithium and ibuprofen was studied in nine male patients admitted to the geropsychiatric ward of a veterans administration medical center. The patients, diagnosed as having bipolar affective disorder or schizoaffective disorder, who had been kept on a steady-state lithium level, received lithium for 3 days, then lithium and ibuprofen (1800 mg/day) for 6 days, and then lithium for 5 days. Ibuprofen increased the serum lithium level and decreased the lithium clearance with marked interindividual variations. These findings indicate that lithium dosage may need to be reduced in some patients following initiation of ibuprofen therapy. There was no significant correlation between changes in lithium serum level and creatinine clearance. The possibility that a tubular renal prostaglandin system may affect lithium excretion needs further investigation.