Drug Interactions between cisplatin and Lithonate

Coadministration with cisplatin may transiently decrease the serum concentrations of lithium. The exact mechanism and clinical significance of the interaction is unknown. In one case, a patient stabilized on lithium demonstrated declines in serum lithium level from 1.0 to 0.3 mEq/L and from 0.8 to 0.5 on two separate occasions following IV administration of cisplatin 100 mg/m2. The decreases occurred over a 24- to 36-hour period following cisplatin administration, and lithium level returned to near baseline by 48 hours to 72 hours. During the first 24 hours of cisplatin administration, the patient also received fluids, sodium, and mannitol, which may have contributed to the interaction. In another case, a patient stabilized on lithium demonstrated a transient 64% decrease in serum lithium level during the first of four courses of cisplatin-based chemotherapy (20 mg/m2 IV on days 1-5). However, the effect became less pronounced during successive courses, with 48%, 37%, and 32% decreases reported. This patient also received hydration and sodium during each course. There was no change in clinical response to lithium in either case. In a third case, lithium levels did not change significantly following initial administration of cisplatin 50 mg/m2 but increased during subsequent courses in association with deterioration of the patient's renal function secondary to progressive disease in both kidneys. Dose adjustments of lithium were required.