Second- and Third-Generation ASMs

Medication Classification – Anticonvulsants

The prototype medication for newer generation ASMs is oxcarbazepine. Doctors use some of these medications in isolation, but many work as adjunct therapy to other seizure medications. Some have therapeutic uses beyond seizures as well. For example, gabapentin treats neuralgia or pain that originates from a nerve, as well as migraines. Lamotrigine can treat bipolar disorder. Topiramate can treat migraines, as well as bipolar disorder.

Other examples of newer generation ASMs include levetiracetam, zonisamide, brivaracetam, and cenobamate.

Expected Pharmacologic Action

Oxcarbazepine was derived from carbamazepine and is structurally similar. It binds to sodium channels, and inhibits the release of glutamate, an excitatoryneurotransmitter.

Adverse Medication Reactions

Adverse drug reactions for oxcarbazepine include dizziness, drowsiness, changes in vision, headache, and ataxia. Similar to carbamazepine, it may cause Steven Johnson syndrome and other dermatological reactions, as well as hypothyroidism and decreased bone mineral density with long-term use. Hematologic effects, such as leukopenia, may occur.

Safety Alert

Hyponatremia may occur, especially if oxcarbazepine is given with diuretics or other medications that decrease sodium levels. If discontinued suddenly, the client is at risk for increased frequency of seizures and status epilepticus.

Interventions

Monitor sodium levels, especially for clients who are also receiving other sodium-depleting medications. When initiating therapy with oxcarbazepine, a low dosage may be given and increased gradually. The total daily dosage is divided into two dosages. Monitor the client’s serum sodium levels, white blood cell count, and complete blood count throughout therapy. If any blood values are outside of the expected reference range, withhold the medication and notify the provider. Test clients of Asian descent for the HLA-B*1502 gene before therapy begins due to an increased risk of severe skin reactions with oxcarbazepine use.

Administration

Oxcarbazepine is administered by oral tablet or liquid.

Client Instructions

Clients should be instructed to always wear protection from sun exposure and to inform their provider if they notice a skin reaction. Clients who use oral contraceptive medications should be instructed to use additional forms of birth control when prescribed oxcarbazepine.

Contraindications and Precautions

Clients who are allergic to carbamazepine should not take oxcarbazepine.

Interactions

Concurrent use with phenytoin may cause elevated serum phenytoin levels, and when used concurrently with phenytoin, phenobarbital, or carbamazepine, decreased serum levels of oxcarbazepine may occur. Oxcarbazepine can reduce the effectiveness of oral contraceptive medications.