5.9 Anticonvulsants V2

Medications used for seizures are called anticonvulsants or antiseizure drugs. Antiseizure drugs stabilize cell membranes and suppress the abnormal electric impulses in the cerebral cortex. These drugs prevent seizures but do not provide a cure. Antiseizure drugs are classified as CNS depressants. There are many types of medications used to treat seizures such as phenytoin, phenobarbital, benzodiazepines, carbamazepine, valproate, and levetiracetam (McCuistion et al, 2018).

There are three main pharmacological effects of antiseizure medications. First, they increase the threshold of activity in the motor cortex, thus making it more difficult for a nerve to become excited. Second, they limit the spread of a seizure discharge from its origin by suppressing the transmission of impulses from one nerve to the next. Third, they decrease the speed of the nerve impulse conduction within a given neuron.

There are over 16 different types of anticonvulsants, all working slightly different to control abnormal electrical activity and to calm excessive firing in the brain.  Many work on blocking sodium/calcium channels, enhance GABAs effects or inhibit the release of excitatory neurotransmitters such as glutamate or aspartate.

Some examples of anticonvulsants are:

• Fatty acid derivative: valproic acid
• Hydantoin: phenytoin sodium
• Triazine: lamotrigine
• Dibenzoazepine: carbamazepine
• Depressants: benzodiazepines and barbiturates

Most anticonvulsants are used for other purposes, not just for managing seizures. Gabapentin, although structurally similar to GABA and classified as an anticonvulsant, is commonly used to control chronic neuropathic pain. Valproic Acid, lamotrigine, and carbamazepine are all used as mood stabilizers to suppress mania and to treat depression in clients with bipolar disorder.

In this unit, we will present six anticonvulsants that are commonly used.

• Anti-seizure treatment: phenytoin, levetiracetam, and gabapentin
• Anti-mania treatment: valproic Acid, lamotrigine, and carbamazepine

Phenytoin

Phenytoin, which was discovered in 1938, was the first anti-seizure medication and is still being used to control seizures (McCuistion et al, 2018).

Mechanism of Action

Phenytoin is in the hydantoin class of anticonvulsants. They are structurally similar to barbiturates. Hydantoins slow the synaptic transmission by blocking sodium channels from recovering from the inactivated state, and inhibits neurons from firing. This stops the repeated excitation of cells that results in seizures (Drugs.com, 2026). As an antiarrhythmic, it shortens the action potential and decreases automaticity.

Indications for Use

Phenytoin is indicated for the treatment of tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures and for the prevention and treatment of seizures occurring during or following neurosurgery. It is also used as an antiarrhythmic, particularly for ventricular dysrhythmias from digoxin toxicity or treatment of prolonged QT interval (Vallerand % Sanoski, 2024).

Nursing Considerations

Administration: oral, IV, IM.

• IV: do not exceed 50 mg per minute in adults and 1 to 3 mg/kg/min (or 50 mg per minute, whichever is slower) in pediatric clients. Risk of severe hypotension and cardiac arrhythmias. Careful cardiac monitoring is needed during and after administering intravenous phenytoin.

Pregnancy: do not administer if pregnant due to risk of harm to fetus.

Phenytoin has a narrow therapeutic drug level, usually between 40 – 80 uM/L, so serum drug monitoring is required (London Health Science Center, 2021). Serum levels of phenytoin sustained above the therapeutic range may produce confusional states referred to as delirium, psychosis, or encephalopathy. Accordingly, at the first sign of acute toxicity, serum levels should be immediately checked.

Abrupt discontinuation can cause status epilepticus, so in the event of an allergic or hypersensitivity reaction, rapid substitution of alternative therapy may be necessary.

Use with caution in clients with renal or hepatic impairment. Elderly clients may require dosage adjustment.

Drug interactions: There are many potential drug interactions with phenytoin. Read drug label information before administering. Phenytoin is extensively bound to plasma proteins and is prone to competitive displacement. Phenytoin is metabolized by hepatic cytochrome P450 enzymes, so it is susceptible to inhibitory drug interactions, which may produce significant increases in circulating phenytoin concentrations and enhance the risk of drug toxicity.

Adverse/Side Effects

Most common side effects include hypotension, diplopia, nystagmus and a rash. Many common effects are nervous system reactions and are dose-related. Reactions include ataxia, slurred speech, decreased coordination, somnolence, and mental confusion (Vallerand & Sanoski, 2024).

Serious and sometimes fatal dermatologic reactions, including toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS), have been reported with phenytoin treatment. The onset of symptoms is usually within 28 days but can occur later. Phenytoin should be discontinued at the first sign of a rash.

Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) has been reported in clients taking antiepileptic drugs, including phenytoin. Some of these events have been fatal or life-threatening. DRESS typically presents with fever, rash, lymphadenopathy, and/or facial swelling, in association with other organ system involvement. These findings should be immediately reported to the provider. Acute hepatotoxicity has been reported with phenytoin. These events may be part of the spectrum of DRESS or may occur in isolation.

Hematopoietic complications, some fatal, have occasionally been reported in association with the administration of phenytoin. These have included thrombocytopenia, leukopenia, granulocytopenia, agranulocytosis, and pancytopenia with or without bone marrow suppression.

Client Teaching

• Clients should be advised to take medications as directed and that doses should be evenly spaced throughout the day.  It may take several weeks to obtain the desired medication effect.
• Abrupt withdrawal of medication may cause status epilepticus.
• Clients should avoid alcohol and other CNS depressants while taking anticonvulsant drug therapy.
• Diabetic clients should monitor their blood glucose levels carefully.
• Gingival hyperplasia – encourage client to perform good oral hygiene.

Phenytoin Medication Card

Now let’s take a closer look at the medication card for phenytoin. Medication cards like this are intended to assist students to learn key points about each medication. Because information about medication is constantly changing, nurses should always consult evidence-based resources to review current recommendations before administering specific medication. Basic information related to each class of medication is outlined below.

Downloadable file (.docx): Phenytoin Medication Card

Levetiracetam

Levetiracetam is a relatively new anticonvulsant and indicated as adjunctive therapy in the treatment of seizures. It is generally well-tolerated with a good safety profile.

Mechanism of Action

The exact mechanism of action is unknown. This medication may interfere with sodium, calcium, potassium, or GABA transmission (DailyMed, n.d.).

Indications for Use

Levetiracetam is indicated as adjunctive therapy in the treatment of partial-onset, myoclonic and tonic-clonic seizures in clients 12 years of age and older with epilepsy.

Nursing Considerations

It is generally well-tolerated. Oral or intravenous administration.

It is safe with children. Suspension formulations for infants.

Monitor:

• Monitor for mood changes
• Assess for suicidal thoughts
• Assess for rash; may cause Stevens-Johnson Syndrome. Discontinue if severe or if fever, malaise and joint aches occur.
• Monitor for DRESS 9fever, rash, lymphadenopathy or facial swelling.

Pregnancy: Plasma levels can gradually decrease during pregnancy and should be monitored closely. Safety not established with breastfeeding.

Risk of withdrawal: Levetiracetam should not be stopped abruptly or withdrawal seizures may occur.

Use with caution in clients with renal impairment. No dosage adjustment for hepatic impairment (Kumar, Maini, & Kadian, 2024; Vallerand & Sanoski, 2024).

Adverse/Side Effects

Most common effects are neurobehavioral and are typically mild: sedation, fatigue, mood swings, headache, agitation, irritability, depression, memory loss, confusion, paresthesia, a decline in cognition, and increased suicide risk. Hypertension can also occur.

Adverse effects are rare and include: psychosis, aggression, hallucinations, and suicidal thoughts. Monitor clients for psychiatric signs and symptoms.

Advise clients not to drive or operate machinery until they have gained sufficient experience on levetiracetam.

This drug can cause anaphylaxis or angioedema after the first dose or at any time during treatment.

Serious dermatological reactions, including Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), have been reported, as well as coordination difficulties and hematologic abnormalities (Vallerand & Sanoski, 2024).

Client Teaching

• Medications should be taken as directed and may cause increased dizziness and somnolence.
• Clients, family, and caregivers should also monitor carefully for suicidality during medication therapy.
• Inform prescriber if they plan to take any OTC or herbal remedies.

Levetiracetam Medication Card

Now let’s take a closer look at the medication card for levetiracetam (DailyMed, n.d.). Because information about medication is constantly changing, nurses should always consult evidence-based resources to review current recommendations before administering specific medication.

Downloadable file (.docx): Levetiracetam Medication Card

Gabapentin

Gabapentin has been used since the 1970’s as an anti-spasmodic. Currently it is used as a muscle relaxant, an antispasmodic and indicated as an adjunct treatment for partial seizures. It is most commonly used to treat neuropathic pain (Lilley et al, 2020). More recently, it is used as part of a multi-modal treatment for post-operative pain to reduce the opioid requirements.

Mechanism of Action

The exact mechanism of action is unknown. It is structurally similar to GABA, but does not act on GABA receptors or influence GABA. It does freely pass through the blood-brain barrier and acts on neurotransmitters.

Indications for Use

Gabapentin is used for partial seizures in adults and children over 3 years of age. It is effective for neuropathic pain, including diabetic neuropathy, postherpetic neuralgia and restless leg syndrome (Yasaei, Katta, Patel, & Saadabadi, 2024).   Neuropathic pain is defined by the International Association for the Study of Pain as “pain caused by a lesion or disease of the somatosensory nervous system” (Murnion, 2018). An example of neuropathic pain is tingling or burning in the lower extremities that often occurs in clients with diabetes. For post-operative pain, it can be used to decrease the amount of opioid use to control pain, along with using acetaminophen.

Off label, it has many uses including bipolar disorder, anxiety disorders, resistant depressants, mood disorders, irritable bowel syndrome, alcohol withdrawal, postoperative analgesia, migraine prophylaxis, and postmenopausal vasomotor symptoms (Yasaei, Katta, Patel, & Saadabadi, 2024).

Nursing Considerations

Oral administration, well absorbed orally. Widely distributed and crosses blood brain barrier. Renal excretion, with t ½ life of 5-7 hours, with complete elimination 2 days.

Pregnancy: Potential harm to fetus such as cardiac defects if multiple doses received. Late pregnancy exposure can lead to small for gestational age and preterm birth.

Pediatrics: Gabapentin use in pediatric clients with epilepsy 3 to 12 years of age is associated with the occurrence of central nervous system-related adverse events. The most significant of these can be classified into the following categories: 1) emotional lability (primarily behavioral problems); 2) hostility, including aggressive behaviors; 3) thought disorder, including concentration problems and change in school performance; and 4) hyperkinesia (primarily restlessness and hyperactivity).

Older adult: peripheral edema and ataxia tend to increase with age. Fall precautions should be considered.

Antiepileptic drugs should not be abruptly discontinued because of the possibility of increasing seizure frequency.

Adverse/Side Effects

More common reactions ataxia, dizziness, fatigue, and fever.

In children, hyperkinesia, concentration difficulties and emotional liability.

Severe reactions: Stevens-Johnson syndrome, anaphylaxis, angioedema, erythema multiforme, rhabdomyolysis, and withdrawal seizure or withdrawal symptoms if the drug is discontinued abruptly.

Depression and suicidality: There is an increased risk of depression, suicidal thoughts or behavior. Clients should be monitored for the emergence of worsening thoughts or behavior, and/or any unusual changes.

Eosinophilia and Systemic Symptoms (DRESS):  also known as multiorgan hypersensitivity, has been reported in clients taking antiepileptic drugs. DRESS usually presents with fever, rash, and/or lymphadenopathy, in association with other organ system involvement. If these symptoms occur, they should be immediately reported to the provider.

Client Teaching

• Clients receiving gabapentin therapy should take medication as directed and be careful not to exceed dosage recommendations.
• Can cause dizziness, somnolence, and other signs of CNS depression. Clients should be advised neither to drive a car nor to operate other complex machinery until they have gained sufficient experience on gabapentin to gauge whether or not it affects their mental and/or motor performance adversely.
• Clients should not take gabapentin within 2 hours of antacid medications.
• Additionally, gabapentin may cause increased drowsiness and dizziness.
• Clients, family, and caregivers should also monitor for suicidality.
• Risk of respiratory depression if taken with CNS depressants.

Gabapentin Medication Card

Now let’s take a closer look at the medication card for gabapentin. Because information about medication is constantly changing, nurses should always consult evidence-based resources to review current recommendations before administering specific medication.

Downloadable file (.docx): Gabapentin Medication Card

The three anticonvulsants used for treatment of mania that will be reviewed are divalproex sodium, carbamazepine and lamotrigine. They are also used for the treatment of seizures.

Divalproex Sodium (Valproate)

Valproate is the first anticonvulsant approved for bipolar disorder. It can help control acute manic episodes. It is equally effective as lithium but it works faster and has less side effects. Lithium has the benefit of reducing suicide risk and preventing relapses, which valproate does not offer.

Adverse/Side Effects

Common side effects include GI distress (nausea, vomiting, diarrhea, dyspepsia, indigestion) and also weight gain. Serious adverse effects include thrombocytopenia, pancreatitis and liver failure.

Monitoring:

Monitor liver enzymes and platelet count periodically.  It can also increase the risk of suicide so monitoring mood and behaviour is vital. CNS toxicity can also occur leading to confusion, dizziness, fatigue, hallucinations and headache (Halter, Pollard & Jacubec, 2019).

Carbamazepine

Carbamazepine is approved for the treatment and prevention of mania in bipolar disorder, although it is less effective in treating depression. It seems to work best for those experiencing anger or are severely paranoid. It is sometimes prescribed for those who are treatment resistant.  Carbamazepine is often used in combinations with lithium or with an antipsychotic (Halter, Pollard & Jacubec, 2019; Burchum Rosenjack & Rosenthal, 2019).

Adverse/Side Effects

Adverse effects include elevating liver enzymes, so close monitoring with weekly LFTs for the first 8 weeks of treatment.

Neurologic side effects such as visual disturbances, ataxia, vertigo, unsteadiness are all common early in treatment.

Rarely, it can cause hematologic symptoms such as leukopenia and aplastic anemia, so periodic complete blood count and platelet count is required.

Drug Interactions: carbamazepine induces P450 enzymes and accelerates its own and other medications metabolism, therefore higher doses may be required. Meds affected are oral contraceptives, warfarin and tricyclic antidepressants (Burchum Rosenjack & Rosenthal, 2019).

Lamotrigine

Lamotrigine is an anticonvulsant to treat seizures and is used as a mood stabilizer for bipolar disorders. It is one of the most prescribed mood stabilizers in the US.

Indications for use:

Lamotrigine is prescribed to treat partial seizures in adults and children with epilepsy and as an adjunct therapy for tonic-clonic seizures. It is also used for maintenance therapy with bipolar disorder (Vallerand & Sanoski, 2024).

Mechanism of Action:

Lamotrigine is a triazine anticonvulsant so structurally different than other anticonvulsants. It acts to stabilize neuronal membranes by inhibiting sodium transport. It acts on the sodium channels and inhibits release of excitatory neurotransmitters, glutamate and aspartate (Vallerand & Sanoski, 2024).

Adverse /Side Effects

Lamotrigine is well tolerated, but serious, rare adverse effects can occur. As with many anticonvulsants, Steven Johnson Syndrome and DRESS can occur. Clients are encouraged to seek medical advice if a rash develops after starting on any anticonvulsant.

Common side effects include ataxia, somnolence, headache, diplopia, blurred vison, nausea, vomiting, rash.

Serious side effects include blood dyscrasias (excess breakdown of red blood cells), increased risk of suicide and serious skin reactions (Steven Johnson Syndrome and DRESS) can occur (Drugs.com, n.d.).

Nursing Considerations

Oral administration, immediate release, extended release and oral disintegrating tablets. Doses are often gradually increased depending on response.  Food does not affect bioavailability.

Often used as an adjunct with other meds.

Do not discontinue abruptly, to minimize risk of a seizure, taper doses over two weeks.

Closely monitor for change in mood or behaviour due to risk of suicidality.

Lactation: do not use while breastfeeding as it is distributed in breast milk.

Client Teaching

• Take medication as prescribed and do not immediately stop the med.
• Inform clients that a rash may develop that can be a serious medical event. Instruct client to seek medical advice immediately.
• The risk of suicidality: may increase the risk of suicidal thoughts or actions so any change in mood, behaviour or actions need to be followed up immediately.
• They may experience side effects such as dizziness, drowsiness so driving or performing hazardous activities should be avoided.
• Pregnancy: If there are plans to get pregnant or are pregnant, consult with prescriber.

References:

Drugs.com (n.d.). Lamotrigine. The American Society of Health System Pharmacists. https://web.archive.org/web/20171210020403/https://www.drugs.com/monograph/lamotrigine.html

Greef, E., Mennie, K. & Muise, A. (2010). Drug Reaction with eosinophilia and systemic symptoms. Canadian Medical Association Journal, 182(5), 481. DOI: https://doi.org/10.1503/cmaj.090709

Halter, M., Pollard, C. & Jacubec, S. (2019). Varcarolis’s Canadian Psychiatric Mental Health Nursing. A clinical approach (2nd ed.). Elsevier: Canada.

Kumar, A., Maini, K.& Kadian, R. (2023). Levetiracetam. National Library of Medicine. Levetiracetam – StatPearls – NCBI Bookshelf

Lilley, L., Collins, S., & Snyder, J. (2020). Pharmacology and the Nursing Process. pp. 246-272. Elsevier. ↵

London Health Science Center. (2021). Phenytoin. https://www.lhsc.on.ca/critical-care-trauma-centre/phenytoin-dilantin ↵

McCuistion, L., Vuljoin-DiMaggio, K., Winton, M, & Yeager, J. (2018). Pharmacology: A patient-centered nursing process approach. pp. 227-305. Elsevier. ↵

Murnion B. P. (2018, June 1). Neuropathic pain: current definition and review of drug treatment. Australian prescriber, 41(3), 60–63. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6003018/ ↵

Rosenjack Burchum, J., & Rosenthal, L. (2019). Lehne’s pharmacology for nursing care (10th ed.). Elsevier: Canada

Vallerand, A. & Sanoski, C. (2024). Davis’s Canadian drug guide for nurses (19th ed.). F.A. Davis Company: Canada

Yasaei, R., Katta, S., Patel, P. & Saadabadi, A. (2024). Gabapentin. National Library of Medicine. Gabapentin – StatPearls – NCBI Bookshelf