NAPLEX Question of the Week: Antiepileptic Drugs (AEDs)

AEDs are an important part of pharmacy practice, especially when it comes to drug interactions. Today's question deals with this facet.

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A 24 year old female with PMH significant only for allergic rhinitis is admitted with what is determined to be a partial onset seizure. She had a one-time seizure approximately 5 years ago which was not treated with AED therapy long-term. Because of the new onset seizure, the decision is made to treat her epilepsy. As an outpatient, she takes loratadine 10mg daily, Flonase nasal spray 1 spray in each nostril daily, and ortho tri-cyclen 1 tablet daily. Which of the following agents is most likely to have minimal interaction with her home medications upon discharge?

A. Oxcarbazepine

B. Divalproex

C. Phenytoin

D. Levetiracetam

Answer with rationale:

The correct answer is D. Levetiracetam (Keppra) is a commonly used AED due to its "clean" pharmacokinetic profile. It is primarily renally excreted with minimal drug interactions and overall is well tolerated. Oxcarbazepine and phenytoin are potent enzyme inducers which could potentially decrease concentrations of her other medications (answers A and C are incorrect). The most concerning interaction would be with her ortho tri-cyclen as this could lead to decreased contraception resulting in pregnancy. Estrogen contraceptives like Ortho Tri Cyclen may increase divalproex concentrations when used together making serum monitoring of divalproex a possibility due to the interaction (answer B). Regardless of which agent is chosen, it is important to remember than hormonal contraception therapy may increase seizure frequency in patients with established epilepsy. Therefore it would be important to determine timing of the initiation of this patients contraception to ensure it is not the cause of her continued seizures as previously she had a one-time seizure that did not require AED therapy.

Christopher M. Bland

Clinical Associate Professor, University of Georgia College of Pharmacy

Comments

Go to the profile of Faiyaz Patel
3 months ago

In above question, Levetricetam concentration expected drop by 50% with tryclcen(COC), in the question not only concer for reductions in COC concentration which can lead to pregnancy but reduction in concentration of Levetircetram which can lower seizure threshold. Here correct answer would be Divalperox because its non enzymes inducing class of AEDs. 

Go to the profile of Christopher M. Bland
3 months ago

Hi Faiyaz- Thank you for your inquiry. I went back and rechecked for an interaction with levetiracetam and Ortho Tri Cyclen both within the package insert and using Lexi-Comp software. Both sources found no interaction between the two agents. Ortho tri cyclen can decrease serum concentrations of valproic acid (or divalproex) by approximately 18 and 29% so serum monitoring may be warranted. Therefore I will update this information in question. Thank you.