NAPLEX Question of the Week: Silencing the Seizures

Today's question will focus on antiepileptic drugs.
NAPLEX Question of the Week: Silencing the Seizures

HJ is a 38 yo female who presents to your locally own pharmacy with a new prescription for Vimpat. HJ has had 3 episodes of seizures despite being on Keppra and her neurologist has prescribed her Vimpat. Her PMH includes epilepsy (partial onset seizures), migraines, and hypothyroidism. She currently takes Keppra 500 mg BID, Imitrex 50 mg PO PRN for migraines, and Synthroid 75 mcg QD. What are appropriate counseling points to give to HJ? (Select all that apply) 

A. Vimpat can be taken as an oral solution or oral tablet.

B. If discontinuation of Vimpat is warranted, it should not be abruptly discontinued in most circumstances.

C. Vimpat may decrease the effectiveness of HJ's sumatriptan.

D. HLA-B 1502 has been identified as a genetic risk factor for Vimpat-induced hypersensitivity reaction.

E. Her current medication Keppra can be taken alongside Vimpat to prevent further seizures.













Answer Choices A, B, and E are correct.

Brand/Generics Covered: Vimpat (lacosamide), Keppra(levetiracetam), Imitrex (sumatriptan), and Synthroid (levothyroxine) 

Epilepsy is a neurological disorder in which abnormal brain activity causes seizures and other disturbances in behavior and sensations. Many anti-epileptic drugs have been created to prevent seizures by inhibiting excitatory pathways or promote inhibitory ones. The efficacy of the drugs is similar, thus when choice of drugs depends on patient specific factors, such as current medications and comorbidities.  

Answer choice A is correct as Vimpat comes in both oral solution and tablet formulations. Also, Vimpat comes in an IV formulation and due to 100% bioavailability of the drug, both IV and oral formulations can be interchanged in a 1:1 ratio. The drug is given twice daily with a max dose of 200 mg BID.  

Answer choice B is correct as with most anti-epileptic medications, abrupt discontinuation can cause a higher risk of seizures. Gradually tapering the medication over the course of a week is recommended when discontinuation is warranted.  In rare circumstances such as an allergic reaction it of course would be stopped abruptly. 

Answer Choice C is incorrect as Vimpat does not appreciably inhibit or induce CYP enzymes. Drugs that decrease the effectiveness of certain medications are CYP inducers. Some anti-epileptic medications that are CYP inducers are phenytoin and phenobarbital. Vimpat is a substrate for CYP3A4, thus dose adjustment may be required when given concomitantly with other medications that affect CYP3A4 like the previously stated anti-epileptics.  

Answer choice D is incorrect as Vimpat does not yet have a genetic allele link to hypersensitivity reactions. Stevens-Johnson Syndrome is a skin and mucous membrane disease caused by a reaction to certain medications. The disease starts with flu-like symptoms followed by severe rash that spreads and blisters, often requiring prompt medical attention. Common anti-epileptic medications that can cause Stevens-Johnson Syndrome are phenytoin, carbamazepine, and lamotrigine. Carbamazepine-induced in particular can be associated with genetic factors such as having the HLA-B 1502 allele, which is more common in those of Chinese origin. These medications require slowly titrating up the dose to monitor for reactions. Vimpat does have a warning/precaution for drug reaction with eosinophilia and and systemic symptoms (DRESS).  

Answer choice E is correct as Vimpat is FDA approved to be administered as monotherapy or adjunctive therapy for partial-onset seizures. Also, there is an adjunctive indication for primary generalized tonic-clonic seizures. The adjunctive dose initial dose (50 mg BID) is half of the initial dose for monotherapy (100 mg BID). Both the max dose for monotherapy and adjunctive therapy is 200 mg BID so titration can be done to this dose.  

One final pearl with Vimpat. It is a controlled substance (CV) and therefore dispensing laws should be taken into account when interpreting prescriptions for this agent. Most of this came from studies at much higher doses demonstrating euphoria similar to alprazolam but this is rare with standard recommended doses as outlined in this question. 

References: Vimpat Package Insert 

NAPLEX Competency Statements: 

1.5 – Signs or symptoms of medical conditions, healthy physiology, etiology of diseases, or pathophysiology 

2.2 – Commercial availability; prescription or non-prescription status; brand, generic, or biosimilar names; physical descriptions; or how supplied 

3.5 – Drug route of administration, dosage forms, or delivery systems 

3.7 – Adverse drug effects, toxicology, or overdose 

3.8 – Drug interactions

As a final note, I am excited to announce that McGraw-Hill and our team have agree to continue the Question of the Week throughout 2023 so look forward to many more outstanding questions from this feature.

Have a great weekend!

Dr. B

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