Home Drug Guide Mephenytoin

Drug Guide

Generic Name

Mephenytoin

Brand Names Mesantoin

Classification

Therapeutic: Anticonvulsant

Pharmacological: Hydantoin derivative

FDA Approved Indications

  • Partial seizures
  • Generalized seizures

Mechanism of Action

Mephenytoin stabilizes neuronal membranes by blocking voltage-dependent sodium channels, reducing neuronal excitability and seizure activity.

Dosage and Administration

Adult: Initial dose: 50-100 mg three times daily, titrated up as needed. Maintenance dose varies.

Pediatric: Dosing based on weight or age; initial: 2-4 mg/kg/day divided into multiple doses.

Geriatric: Start at lower doses due to increased sensitivity and decreased hepatic function.

Renal Impairment: Use caution; dose adjustments may be necessary.

Hepatic Impairment: Use with caution; possibly reduce dose due to hepatic metabolism.

Pharmacokinetics

Absorption: Well absorbed from gastrointestinal tract.

Distribution: Widely distributed; crosses blood-brain barrier.

Metabolism: Primarily hepatic via hydroxylation and conjugation processes.

Excretion: Urinary excretion of metabolites; minimal unchanged drug.

Half Life: Approximately 8-20 hours, varies among individuals.

Contraindications

  • Hypersensitivity to Mephenytoin or hydantoin derivatives.
  • Porphyria.

Precautions

  • Monitor for hypersensitivity reactions, severe skin reactions, blood dyscrasias, gingival hyperplasia, osteomalacia.
  • Use cautiously in hepatic impairment, cardiac disease, or psychosis.
  • Pregnancy Category C: Risks vs. benefits should be considered; potential teratogenicity.

Adverse Reactions - Common

  • Gastrointestinal upset (Rare)
  • Gingival hyperplasia (Less common)
  • Dizziness, drowsiness (Common)

Adverse Reactions - Serious

  • Stevens-Johnson syndrome and toxic epidermal necrolysis (Rare)
  • Blood dyscrasias (agranulocytosis, aplastic anemia) (Rare)
  • SLE-like syndrome (Rare)

Drug-Drug Interactions

  • CNS depressants, warfarin, oral contraceptives, other hepatic enzyme inducers or inhibitors.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Baseline liver function tests, complete blood count, neurological status, gingival condition.

Diagnoses:

  • Risk of bleeding (if blood dyscrasias occur)
  • Risk for infection
  • Altered tissue perfusion

Implementation: Administer with food to reduce gastrointestinal upset. Monitor blood levels if available. Regular dental checkups.

Evaluation: Assessment of seizure control, side effects, and appropriate blood levels if indicated.

Patient/Family Teaching

  • Take medication exactly as prescribed.
  • Report any skin rashes, sore throat, fever, or unusual bleeding.
  • Maintain good oral hygiene to prevent gingival hyperplasia.
  • Regular follow-ups for blood tests and dental health.

Special Considerations

Black Box Warnings:

  • Serious dermatologic reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis).

Genetic Factors: Genetic polymorphisms in CYP enzymes may affect metabolism and toxicity.

Lab Test Interference: Can interfere with certain laboratory assays, including serum amylase and urinary metabolites.

Overdose Management

Signs/Symptoms: Drowsiness, nystagmus, ataxia, coma.

Treatment: Supportive care, activated charcoal if ingestion is recent, and symptomatic treatment. Hemodialysis is generally ineffective.

Storage and Handling

Storage: Store at room temperature, away from moisture and light.

Stability: Stable under recommended storage conditions.

🛡️ 5 Critical Medication Safety Tips for Nurses

1

Triple-Check High-Risk Medications

Always have another nurse verify insulin, heparin, warfarin, and chemotherapy drugs. These "high-alert" medications cause the most serious errors. Check concentration, dose calculation, and pump settings twice.

2

Know Look-Alike, Sound-Alike Drugs

Common mix-ups: hydromorphone/morphine, Celebrex/Celexa, Zyprexa/Zyrtec. Always use BOTH generic and brand names, read labels twice, and use barcode scanning when available. One wrong letter can be fatal.

3

Assess Before AND After Giving Meds

Check vitals before cardiac meds, pain levels before analgesics, and blood glucose before insulin. Always reassess within 30 minutes to evaluate effectiveness and watch for adverse reactions.

4

Watch for Drug Interactions

Common dangerous combinations: warfarin + aspirin (bleeding), ACE inhibitors + potassium (hyperkalemia), digoxin + diuretics (toxicity). Always check drug interactions before administering new medications.

5

Educate Your Patients

Teach patients medication names, purposes, major side effects, and what to report. Informed patients catch errors and improve compliance. Always encourage questions - an educated patient is a safer patient.

⚡ Remember: When in doubt, don't give it out! It's always safer to double-check than regret later.

⚠️ Medical Disclaimer

This drug guide is for educational purposes only and is NOT intended for clinical use. Always consult current prescribing information, healthcare providers, and institutional protocols before administering any medication. Do not use this information for patient care decisions.