Drug Interaction Report

MONITOR: Coadministration of carboplatin with other nephrotoxic agents may increase the risk of renal impairment due to additive effects on the kidney. Moreover, renal impairment secondary to the use of these agents may reduce the clearance of carboplatin, which is primarily eliminated by renal excretion. This may increase the risk of other adverse effects including severe myelosuppression which is concentration-dependent. Approximately 25% of patients receiving carboplatin exhibit decreases in creatinine clearance, whereas rises in serum creatinine and blood urea nitrogen occur less frequently. Some data suggests hypomagnesemia is the primary indicator of carboplatin-induced nephrotoxicity. Patients receiving multiple courses or single doses exceeding 800 mg/m2 of carboplatin, or those with a history of cisplatin-induced nephrotoxicity, may be at increased risk of renal toxicity.

MANAGEMENT: Renal function and serum magnesium levels should be monitored if carboplatin is used concomitantly with other nephrotoxic agents. The potential for increased toxicity of carboplatin such as peripheral sensory neuropathies and myelosuppression should be considered.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

MONITOR: One study has suggested that caffeine withdrawal may significantly increase blood lithium levels. The mechanism may be involve reversal of a caffeine-induced increase in renal lithium excretion.

MANAGEMENT: When caffeine is eliminated from the diet of lithium-treated patients, caution should be exercised. When caffeine consumption is decreased, close observation for evidence of lithium toxicity and worsening of the psychiatric disorder is recommended. Patients should be advised to notify their physician if they experience symptoms of possible lithium toxicity such as drowsiness, dizziness, weakness, ataxia, tremor, vomiting, diarrhea, thirst, blurry vision, tinnitus, or increased urination.