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?
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.