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Antiseizure Drugs

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By Iris Dawn Tabangcora, RN

Antiseizure agents (also known as antiepileptic drugs or anticonvulsants) are drugs used to manage epilepsy, the most prevalent neurological disorder. Antiseizure agents of choice depend on the type of epilepsy, age of the patient, patient tolerance, and specific patient characteristics.

Table of Contents

Antiseizure Agents: Generic and Brand Names

Here is a table of commonly encountered antiseizure agents, their generic names, and brand names:

  • Drugs for generalized seizure
    • Hydratoins
      • ethotoin (Peganone)
      • fosphenytoin (Cerebyx)
      • phenytoin (Dilantin)
    • Barbiturates and Barbiturate-like Drugs
      • mephobarbital (Mebaral)
      • phenobarbital (Solfoton, Luminal)
      • primidone (Mysoline)
    • Benzodiazepines
      • clonazepam (Klonopin)
      • diazepam (Valium)
    • Succinimides
      • ethosuximide (Zarontin)
      • methsuximide (Celontin)
    • Others:
      • acetazolamide (Diamox)
      • valproic acid (Depakene)
      • zonisamide (Zonegran)
  • Drugs for partial seizures
    • carbamazepine (Tegretol, Atretol)
    • clorazepate (Tranxene)
    • gabapentin (Neurontin)

Disease Spotlight: Epilepsy

Epilepsy is a collection of different syndromes, all of which are characterized by sudden discharge of excessive electrical energy from nerve cells located within the brain. The resultant reaction is called

The nature of seizures depends on the location of the cells that initiate the electrical discharge as well as the neural pathways which were stimulated. Seizures can be primary (no underlying cause) or secondary (brought about by external factors like head injury).

Status epilepticus is a state in which seizures rapidly recur with no recovery between seizures. It is potentially the most dangerous of seizures. 

International Classification of Seizures categorized seizures based on symptoms and characteristics. The two main categories include:

Generalized Seizures

These seizures are characterized by a massive electrical activity that begins in one area of the brain and rapidly spreads to both hemispheres. It is usually accompanied by loss of consciousness. It is further classified into five types:

Tonic-clonic seizure

It involves involuntary muscle contraction (tonic) followed by relaxation appearing as an aggressive spasm (clonic), loss of consciousness, and confusion and exhaustion in the early recovery period. 

Absence seizure

It is an abrupt and brief (3-5 s) period of loss of consciousness common in children (starting at age 3) but frequently disappears by puberty. This seizure does not usually involve muscle contractions.

Myoclonic seizure

It is characterized by short, sporadic periods of muscle contractions that last for several minutes. It is relatively rare. 

Febrile seizure

Self-limited seizures are related to very high fevers and usually involve tonic-clonic seizures. This type most frequently occurs in children.

Jacksonian Seizures

Begins in one area of the brain and involve only one part of the body but this later on spread to other parts until a generalized tonic-clonic seizure has developed.

Partial (Focal) Seizures

These are characterized by seizures that originate from one area of the brain which do not spread to other parts. It can be further classified into two:

Simple Partial Seizure

It occurs in a single area of the brain and may involve a single muscle movement or sensory alteration. 

Complex Partial Seizure

It is a type that occurs in the late teenage years and involves a series of reactions or emotional changes and complex sensory changes (hallucinations, mental distortion, personality changes, loss of consciousness, and loss of social inhibition). Motor changes may include involuntary urination, chewing motions, and diarrhea.

Drugs for Treating Generalized Seizures

Drugs used for the treatment of generalized seizures exert their therapeutic effects by blocking channels in the cell membrane or by altering their receptor sites. As a result, nerve membranes become stabilized. Their work involves the entire nervous system so sedation is an expected result.

Drugs used to treat generalized seizures include hydantoins, barbiturates, barbiturate-like drugs, benzodiazepines, and succinimides.

Succinimides and drugs that modulate the inhibitory GABA are used to treat absence seizures.

Hydantoins

Therapeutic Action

The desired and beneficial actions of hydantoins are as follows:

  • Stabilize the CNS nerve membranes by decreasing the excitability and hyperexcitability of ionic channels in the cell membrane to stimulation.
  • Decreasing the conduction through nerve pathways reduce the tonic-clonic, muscular, and emotional responses to stimulation.

Indications

Hydantoins are indicated for the following medical conditions:

  • Control of tonic-clonic and psychomotor seizures, prevention of seizures during neurosurgery, control of status epilepticus
  • Less likely to cause sedation which makes them the drug of choice for patients who are not willing to tolerate sedation and drowsiness.
  • However, this class have severe adverse effects that benzodiazepines have replaced them in man situations

Here are some important aspects to remember for indication of hydantoins in different age groups:

Children

  • They are more sensitive to the sedating effects of the drugs so frequent and close monitoring is required.
  • Antiepileptic or antiseizure drugs can impact learning and social development.
  • Parents of these children should receive consistent support and education about seizure disorder and medications.

Adults

  • They should receive regular care and close monitoring for adverse effects.
  • Adults taking this drugs are encouraged to wear MedicAlert identification during emergency instances.
  • Education about the disorder, lifestyle changes, medications, and handling stigma should be given focus.
  • Caution for use of these drugs to pregnant and lactating women is exercised because some medications are linked to fetal abnormalities in animal studies while some are clearly associated with predictable congenital effects in humans.
  • Use of barrier contraception and alternative methods for feeding are encouraged.
  • Stopping antiepileptic can precipitate seizures and would lead to anoxia.

Older adults

  • They are more susceptible to adverse effects of the drug because of possible problems in metabolism and excretion.
  • There may be a need to reduce drug dosage.

Pharmacokinetics

Here are the characteristic interactions of hydantoins and the body in terms of absorption, distribution, metabolism, and excretion:

RouteOnsetPeakDuration
OralSlow2- 12 h6-12 h
IV1-2 hRapid12-24 h
Half-life (T1/2)MetabolismExcretion
6-24 hLiverKidney (urine)

Contraindications and Cautions

The following are contraindications and cautions for the use of hydantoins:

  • Allergy to hydantoins. Prevent hypersensitivity reactions
  • Pregnancy, lactation. Possible problems to the fetus or the newborn.
  • Debilitated patients. May respond adversely to CNS depression
  • Impaired hepatorenal function. Interfere with drug metabolism and excretion
  • Coma, depression, psychoses. Can be exacerbated by the generalized CNS depression

Adverse Effects

Use of hydantoins may result to these adverse effects:

Interactions

The following are drug-drug interactions involved in the use of hydantoins:

  • Alcohol: increased risk of CNS depression
  • Evening primrose: increased risk of seizures
  • Ginkgo: increased risk of serious adverse effects together with phenytoin

Barbiturates and Barbiturate-like Drugs

Therapeutic Action

The desired and beneficial action of barbiturates and barbiturate-like drugs is:

  • Inhibit impulse conduction in the ascending RAS, depress cerebral cortex, alter cerebral function, and depress motor nerve input.

Indications

Barbiturates and barbiturate-like drugs are indicated for the following medical conditions:

  • Control of tonic-clonic and psychomotor seizures, prevention of seizures during neurosurgery, control of status epilepticus
  • Similar with hydantoins, they are capable of stabilizing CNS nerve membranes by directly influencing the ionic channels in the cell membrane resulting to decreased excitability and hyperexcitability to stimulation.
  • Phenobarbital depresses lower brainstem, cerebral cortex, and motor conduction.
  • Aside for being used as treatment for tonic-clonic and absence seizures, mephobarbital is also used as an anxiolytic or hypnotic agent.

Here are some important aspects to remember for indication of barbiturates and barbiturate-like drugs in different age groups:

Children

  • They are more sensitive to the sedating effects of the drugs so frequent and close monitoring is required.
  • Antiepileptic or antiseizure drugs can impact learning and social development.
  • Parents of these children should receive consistent support and education about seizure disorder and medications.

Adults

  • They should receive regular care and close monitoring for adverse effects.
  • Adults taking this drugs are encouraged to wear MedicAlert identification during emergency instances.
  • Education about the disorder, lifestyle changes, medications, and handling stigma should be given focus.

Pregnant women

  • Caution for use of these drugs to pregnant and lactating women is exercised because some medications are linked to fetal abnormalities in animal studies while some are clearly associated with predictable congenital effects in humans.
  • Use of barrier contraception and alternative methods for feeding are encouraged. Stopping antiepileptic can precipitate seizures and would lead to anoxia.

Older adults

  • They are more susceptible to adverse effects of the drug because of possible problems in metabolism and excretion.
  • There may be a need to reduce drug dosage.

Pharmacokinetics

Here are the characteristic interactions of barbiturates and barbiturate-like drugs and the body in terms of absorption, distribution, metabolism, and excretion:

RouteOnsetPeakDuration
Oral30-60 minN/A10-16 h
IM, subcutaneous10-30 minN/A4-6 h
IV5 minN/A4-6 h
Half-life (T1/2)MetabolismExcretion
79 hLiverKidney (urine)

Contraindications and Cautions

  • Same with those discussed for hydantoins

Adverse Effects

  • CNS: depression, confusion, drowsiness, lethargy, fatigue, sedation, hypnosis, anesthesia, deep coma
  • CV: arrhythmias, changes in blood pressure
  • GI: constipation, dry mouth, anorexia
  • GU: urinary retention, loss of libido
  • Others: physical dependence, withdrawal symptoms, severe dermatological reactions
  • Mephobarbital is commonly associated with CNS and GI effects. It can also cause circulatory collapse and apnea which makes it less desirable compared to other antiseizure agents.

Interactions

  • Alcohol: increased risk of CNS depression
  • Ginkgo: increased risk of serious adverse effects

Benzodiazepines

Therapeutic Action

The desired and beneficial action of benzodiazepines is as follows:

  • Potentiate effects of GABA (inhibitory neurotransmitter that stabilizes nerve cell membranes).
  • Act primarily in the limbic system and RAS so it can also cause muscle relaxation and relief of anxiety without substantially affecting the functions of the cortex.

Indications

Benzodiazepines are indicated for the following medical conditions:

  • Used as adjunct to treatment of status epilepticus and severe recurrent convulsive seizures. Also used to manage epilepsy in patients who require intermittent use to control bouts of increased seizure activity.
  • In addition to this, it can be used as agent to relieve anxiety before operative interventions.

Here are some important aspects to remember for indication of benzodiazepines in different age groups:

Children

  • They are more sensitive to the sedating effects of the drugs so frequent and close monitoring is required.
  • Antiepileptic or antiseizure drugs can impact learning and social development.
  • Parents of these children should receive consistent support and education about seizure disorder and medications.

Adults

  • They should receive regular care and close monitoring for adverse effects.
  • Adults taking this drugs are encouraged to wear MedicAlert identification during emergency instances.
  • Education about the disorder, lifestyle changes, medications, and handling stigma should be given focus.

Pregnant women

  • Caution for use of these drugs to pregnant and lactating women is exercised because some medications are linked to fetal abnormalities in animal studies while some are clearly associated with predictable congenital effects in humans.
  • Use of barrier contraception and alternative methods for feeding are encouraged. Stopping antiepileptic can precipitate seizures and would lead to anoxia.

Older adults

  • They are more susceptible to adverse effects of the drug because of possible problems in metabolism and excretion.
  • There may be a need to reduce drug dosage.

Pharmacokinetics

Here are the characteristic interactions of benzodiazepines and the body in terms of absorption, distribution, metabolism, and excretion:

RouteOnsetPeakDuration
Oral30-60 min1-2 h3 h
IM15-30 min30-45 min3 h
IV1-5 min30 min15-60 min
RectalRapid1.5 h3 h
Half-life (T1/2)MetabolismExcretion
20-80 hLiverKidney (urine)

Contraindications and Cautions

The following are contraindications and cautions for the use of benzodiazepines:

  • Same with those discussed for hydantoins

Adverse Effects

Use of benzodiazepines may result to these adverse effects:

Interactions

The following are drug-drug interactions involved in the use of benzodiazepines:

  • Alcohol: increased risk of CNS depression

Succinimides

Therapeutic Action

The desired and beneficial action of succinimides is as follows:

  • Act in inhibitory neuronal systems and suppress the electroencephalographic pattern associated with absence seizures.

Indications

Succinimides are indicated for the following medical conditions:

  • Most frequently used to treat absence seizures and reduction of frequency of attacks

Here are some important aspects to remember for indication of succinimides in different age groups:

Children

  • They are more sensitive to the sedating effects of the drugs so frequent and close monitoring is required.
  • Antiepileptic or antiseizure drugs can impact learning and social development.
  • Parents of these children should receive consistent support and education about seizure disorder and medications. 

Adults

  • They should receive regular care and close monitoring for adverse effects.
  • Adults taking these drugs are encouraged to wear MedicAlert identification during emergency instances.
  • Education about the disorder, lifestyle changes, medications, and handling stigma should be given focus.
  • Stopping antiepileptic can precipitate seizures and would lead to anoxia.
  • Use of barrier contraception and alternative methods for feeding are encouraged.

Pregnant women

  • Caution for use of these drugs to pregnant and lactating women is exercised because some medications are linked to fetal abnormalities in animal studies while some are clearly associated with predictable congenital effects in humans.

Older adults

  • They are more susceptible to adverse effects of the drug because of possible problems in metabolism and excretion.
  • There may be a need to reduce drug dosage.

Pharmacokinetics

Here are the characteristic interactions of succinimides and the body in terms of absorption, distribution, metabolism, and excretion:

RouteOnsetPeakDuration
OralN/A3-7 hN/A
Half-life (T1/2)MetabolismExcretion
30 h (children), 60 h (adults)LiverKidney (urine), liver (bile)

Contraindications and Cautions

The following are contraindications and cautions for the use of succinimides:

  • Same with those discussed for hydantoins

Adverse Effects

Use of succinimides may result to these adverse effects:

  • CNS: depression, drowsiness, fatigue, ataxia, insomnia, headache, blurred vision
  • GI: decreased GI activity, nausea, vomiting, anorexia, weight loss, GI pain, constipation or diarrhea
  • Direct chemical irritation of the skin and bone marrow: bone marrow suppression, fatal pancytopenia, urticarial, alopecia, Steven-Johnson’s syndrome
  • Ethosuximide has relatively few adverse effects compared with may antiseizure agents.

Interactions

The following are drug-drug interactions involved in the use of succinimides:

  • Primidone: decreased primidone serum levels

Drugs for Treating Partial Seizures

  • Partial seizures can be either simple (single muscle or reaction) or complex (series of reactions or emotional changes).

Therapeutic Action

The desired and beneficial actions of drugs used for treatment of partial seizures are as follows:

  • Drugs used to control partial seizures stabilize nerve membranes either by altering sodium and calcium channels or by increasing the activity of inhibitory neurotransmitter GABA.
  • Carbamazepine inhibits polysynaptic responses and blocks sodium channels to prevent formation of repetitive action potentials. It is chemically related to TCAs.
  • Clorazepate and felbamate potentiate the effects of GABA.
  • Gabapentin blocks polysynaptic responses and stimulus increases in certain situations.

Indications

Drugs used for treatment of partial seizures are indicated for the following medical conditions:

  • Carbamazepine, felbamate, and oxcarbazepine are used as monotherapy. The remaining drugs are used as adjunctive therapy.

Pharmacokinetics

Here are the characteristic interactions of drugs used for treatment of partial seizures and the body in terms of absorption, distribution, metabolism, and excretion:

DrugsOnsetPeakDurationT 1/2Metabolism and Excretion
Carbamazepine (oral)N/AN/AN/A25-65 hLiver, kidney (urine)
Clorazepate (oral)Rapid1-2 hN/A30-100 hLiver, kidney (urine)
Gabapentin (oral)N/AN/AN/A5-7 hN/A, kidney (urine; unchanged_

Contraindications and Cautions

The following are contraindications and cautions for the use of drugs indicated for treatment of partial seizures:

  • Allergy to antiseizure agents. Prevent hypersensitivity reactions
  • Bone marrow suppression. Exacerbated by drug effects.
  • Severe hepatic dysfunction. Interferes with drug metabolism
  • Pregnancy. Carbamazepine, clorazepate, and gabapentin have been shown dangerous to fetus
  • Renal stones. Can be exacerbated by drug effects

Adverse Effects

Use of drugs indicated for treatment of partial seizures may result to these adverse effects:

  • CNS: drowsiness, fatigue, weakness, confusion, headache, insomnia
  • Respiratory: upper respiratory infections
  • GI: GI depression, nausea, vomiting, anorexia
  • Pregabalin is a category V controlled substance (can cause feelings of well-being and euphoria). It is also related to CNS depression characterized by somnolence, dizziness, and visual changes.

Interactions

The following are drug-drug interactions involved in the use of drugs indicated for treatment of partial seizures:

  • Other CNS depressants, alcohol: increased risk of CNS depression

Nursing Considerations

Here are important nursing considerations when administering this drug:

Nursing Assessment

These are the important things the nurse should include in conducting assessment, history taking, and examination:

  • Assess for mentioned contraindications and cautions (e.g. drug allergy, diabetes, hepatorenal dysfunction, arrhythmias, hypotension, etc.) to prevent untoward complications.
  • Assess for the description (onset, aura, duration, recovery) of seizures to determine type of seizure and establish a baseline.
  • Perform a thorough physical assessment (skin color and lesions, vital signs, level of orientation, affect, reflexes, bowel sounds, urine output, etc.) to obtain baseline data and monitor changes associated with adverse effects.
  • Monitor results of laboratory tests (renal and liver function) to determine appropriateness of therapy and possibility of dose adjustment.

Nursing Diagnoses

Here are some of the nursing diagnoses that can be formulated in the use of this drug for therapy:

Implementation with Rationale

These are vital nursing interventions done in patients who are antiseizure agents:

  • Monitor for adverse effects and provide appropriate supportive care as needed to help patient cope with these effects.
  • Monitor CBC results to detect bone marrow suppression early and provide prompt intervention.
  • Discontinue the drug at any sign of hypersensitivity reaction, liver dysfunction, and severe skin rash to limit reaction and prevent potentially serious reactions.
  • Provide comfort measures (e.g. positioning of legs and arms for dyskinesia, sugarless candy and ice chips for dry mouth, voiding before taking drugs for urinary hesitancy or retention, etc.) to help patient tolerate drug effects.
  • Provide safety measures (e.g. adequate lighting, raised side rails, etc.) to prevent injuries.
  • Educate client on drug therapy to promote understanding and compliance.

Evaluation

Here are aspects of care that should be evaluated to determine effectiveness of drug therapy:

  • Monitor patient response to therapy (decrease in incidence or absence of seizures).
  • Monitor for adverse effects (e.g. CNS changes, GI depression, bone marrow suppression, severe dermatological reactions, liver toxicity, etc).
  • Evaluate patient understanding on drug therapy by asking patient to name the drug, its indication, and adverse effects to watch for.
  • Monitor patient compliance to drug therapy.

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References and Sources

References and sources for this pharmacology guide for antiseizure agents:

  • Karch, A. M., & Karch. (2011). Focus on nursing pharmacology. Wolters Kluwer Health/Lippincott Williams & Wilkins. [Link]
  • Katzung, B. G. (2017). Basic and clinical pharmacology. McGraw-Hill Education.
  • Lehne, R. A., Moore, L. A., Crosby, L. J., & Hamilton, D. B. (2004). Pharmacology for nursing care.
  • Smeltzer, S. C., & Bare, B. G. (1992). Brunner & Suddarth’s textbook of medical-surgical nursing. Philadelphia: JB Lippincott.
Iris Dawn is a nurse writer in her 20s who is on the constant lookout for latest stories about Science. Her interests include Research and Medical-Surgical Nursing. She is currently furthering her studies and is seriously considering being a student as her profession. Life is spoiling her with spaghetti, acoustic playlists, libraries, and the beach.

1 thought on “Antiseizure Drugs”

  1. Not bad – however please make sure your research is current in this area. One of your barbiturates is no longer available – it has been discontinued. Phenobarbital is able to be given daily, so it is active in the system for > 24 hours. Also, some of your drug classifications aren’t correct. The most up to date anticonvulsant drug list is available at epilepsy.com. The Epilepsy Foundation makes certain the information they provide is up to date – used them all through my early adult years and still do. They don’t have the classifications available, but those are easy even from a resource such as drugs.com who provides the PDR drug information. Epilepsy Foundation’s website also has the most up to date terminology used in relation to seizure types. Jacksonian isn’t even used anymore. You missed Ativan – our emergency benzodiazepine for status epilepticus. You totally missed Depakote (sodium valproate), Keppra, Lamictal, and Lyrica to name a few others that are more common than Zarontin, Celontin, and Zonegran – depending on where you are anyway. Trying not to be overly critical – but if you really are into research – please make sure it is correct before you publish. As I said, not only am I a “patient” with the above condition for these medication classes, but I have been a nurse for 10 years now. While my resources may not be that scholarly – think AJN, NEJM, etc; they are more reliable than google.com. Thank you.

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