Role of Antiepileptic Drugs (continued)

A recently reported pilot study found oxcarbazepine monotherapy (which does not appear to involve neurocognitive risks for patients with cancer)7 to be associated with significantly reduced seizure rates (P=0.002) at a mean dose of 1,230 mg/day.9 Valproic acid, levetiracetam, and lamotrigine are also commonly prescribed for seizures among patients with cancer; a recent review listed combination antiepileptic drug regimens (valproic acid + lamotrigine or levetiracetam, and levetiracetam + topiramate) as potentially “useful” for this purpose.1,10


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Potential Drug Interactions

An important consideration is the potential impact of drug interactions between antiepileptic drugs and chemotherapy agents and other drugs commonly prescribed to patients with cancer. Enzyme-inducing antiepileptics (including oxcarbazepine, carbamazepine, phenytoin, and phenobarbital, for example) can reduce the efficacy of several anticancer chemotherapy drugs, with which they should not be co-administered (Table 1).1

Table 1. Anti-Neoplastics to Avoid with Enzyme-inducing Antiepileptics

Alkylating agents

Ifosfamide

Taxanes:
Paclitaxel
Docetaxel
Targeted agents:
Bortezomib
Imatinib
Erlotinib
Gefitinib
Sorafenib
Everolimus
Temsirolimus
Vemurafenib
Others:

Etoposide
Methotrexate
Pemetrexed

Topoisomerase Inhibitors:

Irinotecan
Topotecan

 

Source/Credit: Weller et al.

Corticosteroids are very frequently administered to patients with brain tumors, but phenytoin, carbamazepine, and phenobarbital—commonly prescribed to reduce seizures—can impair corticosteroid efficacy.8 It is also the case that corticosteroids and many anticancer chemotherapy drugs affect antiepileptic drug metabolism, causing under- and overdosing and impaired efficacy.8

Patient Considerations and Current Clinical Evidence

In addition to side effects and potential adverse drug interactions, prescribing antiepileptics to patients with cancer must also be preceded by careful consideration of the potential harms of these drugs to patients’ memory and their affect on neurocognitive deterioration. These neurocognitive effects not only can harm quality of life for the patient because the resulting symptoms can mimic tumor progression, but these medications can sometimes also complicate assessment of anticancer treatment effects.7