Chapter 23 anti seizure agents Flashcards
Hydantoins MEDS
Phenytoin (Dilantin)
Fosphenytoin (Cerebyx, Sesquient).
MOA hydantoins
Hydantoins stabilize nerve membranes throughout the central nervous system (CNS).
They influence ionic channels in the cell membrane, thereby decreasing excitability and hyperexcitability.
This reduces conduction through nerve pathways, diminishing tonic-clonic, muscular, and emotional responses to stimulation.
Indications: hydantoins
Control of tonic- clonic (grand mal) and psychomotor seizures.
Prevention of seizures during neurosurgery.
Management of status epilepticus (a life-threatening seizure condition).
Pharmacokinetics hydantoins
Phenytoin:
- Well absorbed in the
GI tract.
- Metabolized in the
liver, excreted in urine.
- Therapeutic serum
levels: 10-20 mcg/mL.
- Available in oral and
parenteral (IV) forms.
Fosphenytoin:
- Given intramuscularly
(IM) or intravenously
(IV).
- Metabolized in the
liver, excreted in urine.
- Therapeutic levels peak within 10-20
minutes after infusion.
CI hydantoins
Allergy to hydantoins (risk of hypersensitivity reactions).
Pregnancy and lactation – associated with specific congenital anomalies.
- Use only if the risk of seizures
outweighs fetal risks.
- Barrier contraceptives recommended.
Severe hepatic or renal impairment
(risk of drug accumulation and toxicity).
Coma, depression, or psychoses (can worsen CNS depression).
Older adults or debilitated patients
(may be more sensitive to CNS effects) .
AE hydantoin
CNS Effects: Depression, confusion, drowsiness, lethargy, fatigue.
Gastrointestinal (GI) Effects: Constipation, dry mouth, anorexia.
Cardiovascular Effects: Cardiac arrhythmias, blood pressure changes.
Genitourinary (GU) Effects: Urinary retention, loss of libido.
Severe Effects:
- Liver toxicity.
- Bone marrow suppression.
- Gingival hyperplasia
(overgrowth of gum tissue).
- Severe dermatological reactions (e.g., Stevens- Johnson syndrome, hirsutism).
- Malignant lymphoma (rare).
DDI hydantoins
Alcohol and other CNS depressants: Increased CNS depression.
Evening primrose (herbal supplement): Increases seizure risk.
Ginkgo biloba: Reduces phenytoin effectiveness.
Always consult a provider before adding or stopping medications due to significant drug interactions.
Nursing interventions hydantoins
Monitor serum phenytoin levels (10-20 mcg/mL) to ensure therapeutic range.
Assess for hypersensitivity reactions, liver dysfunction, or severe skin rashes.
Monitor cardiovascular status carefully during IV infusion of fosphenytoin.
Educate patients:
- Do not abruptly stop the medication (risk of status
epilepticus).
- Practice good oral hygiene to prevent gingival
hyperplasia.
- Use barrier contraceptives to prevent pregnancy-
related risks.
- Avoid alcohol and CNS depressants.
- Check with healthcare providers before taking
herbal supplements.
Ensure patient identification and medication verification to avoid confusion with sound-alike drugs (e.g., Celecoxib, Citalopram, Alprazolam).
Carbamazepine: MEDS, MOA, indications, Pharmacokinetics
MEDS: Tegretol, Epitol
Mechanism of Action:
- Inhibits polysynaptic responses and blocks sodium channels, preventing
repetitive action potentials in neurons.
Indications:
- Generalized and focal seizures
- Trigeminal neuralgia
Pharmacokinetics:
- Absorbed in the GI tract, metabolized in the liver via the cytochrome P450
system.
- Excreted in urine.
- Half-life: 25 to 65 hours.
Carbamazepine CI, AE, DDI
Contraindications and Cautions:
- Serious dermatologic reactions (Stevens-Johnson Syndrome, Toxic
Epidermal Necrolysis) – increased risk in patients with HLA-B*1502 allele.
- Hematologic disorders (risk of aplastic anemia and agranulocytosis).
- Pregnancy Risk: Linked to spina bifida and congenital defects.
Adverse Effects:
- Drowsiness, dizziness, nausea, vomiting, hepatitis.
- Stevens-Johnson syndrome.
- Hematologic disorders (aplastic anemia, agranulocytosis).
Drug and Food Interactions:
- Grapefruit juice increases toxicity.
- Strong CYP450 inducer, reducing levels of oral contraceptives, warfarin,
corticosteroids.
Nursing interventions for carbamazepine
- Screen for dermatologic reactions before initiating therapy.
- Monitor complete blood count (CBC) regularly due to hematologic risks.
- Educate patients to avoid grapefruit juice.
- Use alternative birth control methods.
Lamotrigine MED, MOA, Indication, Pharmacokinetics
(Lamictal)
Mechanism of Action:
- Inhibits voltage-sensitive sodium and calcium channels. - Modulates neurotransmitter release to stabilize nerve cell
membranes.
Indications:
- Generalized and focal seizures.
- Bipolar disorder (mood stabilization).
Pharmacokinetics:
- Rapidly absorbed and metabolized in the liver.
- Excreted in urine.
- Half-life: ~25 hours.
Lamotrigine CI, AE, DDI
Contraindications and Cautions:
- Serious dermatologic reactions (Stevens-Johnson
Syndrome, Toxic Epidermal Necrolysis).
- Higher risk in pediatric patients and when combined
with valproate.
Adverse Effects:
- Severe skin reactions, blurred vision, dizziness, drowsiness, nausea.
Drug and Food Interactions:
- Valproate increases lamotrigine levels (dose reduction
needed).
Nursing interventions for Lamotrigine
- Monitor for rash closely; discontinue if rash appears. - Caution when co-administering with valproate.
- Advise patients to report any signs of skin reactions
immediately.
Levetiracetam MEDS, MOA, indications, pharmacokinetics
(Keppra, Elepsia XR, Spritam)
Mechanism of Action:
- Unknown, but suppresses rapid neuronal firing
without affecting normal excitability.
Indications:
- Generalized and focal seizures.
Pharmacokinetics:
- Rapid absorption, peak level in 1 hour.
- Minimal metabolism, primarily excreted unchanged
in urine.
- Half-life: 6 to 8 hours.
Levetiracetam CI, AE, DDI
Contraindications and Cautions:
- Monitor pregnancy-related serum level changes
(pregnancy decreases drug levels).
Adverse Effects:
- Fatigue, dizziness, behavioral changes, aggression, suicidal thoughts.
Drug and Food Interactions:
- Minimal drug interactions compared to other AEDs.
Nursing intervention for levetiracetam
- Monitor mood and behavioral changes (risk of
aggression and suicidal ideation). - Assess kidney function before initiating therapy. - Warn patients about potential drowsiness and
dizziness.
Topiramate MEDS, MOA, indication, Pharmacokinetics
Mechanism of Action:
- Blocks sodium channels, enhances GABA activity, inhibits glutamate receptors, and inhibits carbonic anhydrase enzyme.
Indications:
- Generalized tonic-clonic seizures (including Lennox-Gastaut
syndrome).
- Migraine prevention.
Pharmacokinetics:
- Absorbed through the GI tract, not significantly metabolized. - Excreted primarily unchanged in urine.
- Half-life: 31 hours.
Topiramate CI, AE, DDI
Contraindications and Cautions:
- Fetal risks: Associated with cleft lip, cleft palate, and low birth
weight.
- Monitor kidney function closely due to renal excretion.
Adverse Effects:
- Cognitive dysfunction (“brain fog”), weight loss, kidney
stones, metabolic acidosis, heat intolerance.
Drug and Food Interactions:
- Increases phenytoin and valproate toxicity.
- May reduce oral contraceptive effectiveness.
Nursing interventions topiramate
- Monitor kidney function and hydration levels to prevent
kidney stones. - Assess cognitive function and mental alertness.
- Encourage increased fluid intake to reduce kidney stone risk. - Educate female patients on alternative contraception.
