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An interaction between cytostatic and anticonvulsant drugs
C Neef1, I de Voogd-van der Straaten
1Department of Pharmacy, St. Antonius Hospital, Nieuwegein, The Netherlands.
Clinical Pharmacology and Therapeutics
|April 1, 1988
Summary
Antineoplastic therapy with cisplatin and adriamycin significantly lowered levels of antiepileptic drugs like carbamazepine, valproate sodium, and phenytoin in epilepsy patients. This suggests altered drug absorption, elimination, or distribution during chemotherapy.
Area of Science:
- Pharmacology
- Oncology
- Neurology
Background:
- Epilepsy management requires consistent therapeutic drug levels.
- Antineoplastic agents can interfere with the pharmacokinetics of other medications.
Observation:
- A patient with epilepsy experienced seizures during adriamycin and cisplatin chemotherapy.
- Plasma levels of phenytoin, carbamazepine, and valproate sodium were monitored during chemotherapy cycles.
Findings:
- Carbamazepine and valproate sodium levels decreased during chemotherapy, returning to normal post-treatment.
- Phenytoin levels dropped significantly, even when administered intravenously, suggesting increased metabolism or distribution volume.
- Cisplatin may alter phenytoin's metabolic rate (Michaelis-Menten parameters) or increase its volume of distribution.
Implications:
- Chemotherapy can significantly impact the efficacy of antiepileptic drugs.
- Close therapeutic drug monitoring is crucial for epilepsy patients undergoing cancer treatment.
- Further research is needed to elucidate the mechanisms behind altered drug pharmacokinetics during chemotherapy.