Home Drug Guide Primidone

Drug Guide

Generic Name

Primidone

Brand Names Mysoline

Classification

Therapeutic: Anticonvulsant/Antiepileptic

Pharmacological: Prodrug for phenobarbital and phenylethylmalonamide

FDA Approved Indications

  • Epilepsy (partial seizures, generalized tonic-clonic seizures)

Mechanism of Action

Primidone is metabolized into phenobarbital and phenylethylmalonamide, which enhance GABA-mediated neuronal inhibition, stabilizing neuronal membranes and reducing seizure activity.

Dosage and Administration

Adult: Initial dose: 125-250 mg at bedtime; titrate slowly. Maintenance doses vary.

Pediatric: Dosing based on weight and age, typically starting at 50 mg/day divided doses.

Geriatric: Start at lower dose due to increased sensitivity and risk of adverse effects.

Renal Impairment: Use cautiously; dosage adjustments may be necessary.

Hepatic Impairment: Monitor closely; dosage adjustments recommended.

Pharmacokinetics

Absorption: Well absorbed from gastrointestinal tract.

Distribution: Widespread, crosses blood-brain barrier.

Metabolism: Metabolized in the liver into active metabolites (phenobarbital).

Excretion: Primidone and metabolites excreted primarily in urine.

Half Life: Primidone: approximately 3-7 hours; active metabolites longer.

Contraindications

  • Hypersensitivity to primidone, barbiturates, or related drugs.
  • Porphyria.

Precautions

  • Use cautiously in hepatic impairment, pregnancy, lactation, and with other CNS depressants. Monitor blood counts.

Adverse Reactions - Common

  • Drowsiness, dizziness (Common)
  • Nausea, vomiting (Common)
  • Ataxia, nystagmus (Common)

Adverse Reactions - Serious

  • Agranulocytosis, aplastic anemia (Serious but rare)
  • Severe hypersensitivity reactions (Rare)
  • Stevens-Johnson syndrome (Rare)

Drug-Drug Interactions

  • Other CNS depressants, warfarin, oral contraceptives, strong CYP450 inducers or inhibitors.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor seizure control, hepatic function, blood counts, and CNS status.

Diagnoses:

  • Risk for falls due to sedation
  • Risk for decreased activity tolerance

Implementation: Administer with food to decrease gastric upset, titrate slowly, monitor blood levels if indicated.

Evaluation: Evaluate seizure frequency, adverse effects, and laboratory parameters regularly.

Patient/Family Teaching

  • Take medication exactly as prescribed.
  • Do not stop suddenly—risk of withdrawal seizures.
  • Report signs of allergic reactions or blood dyscrasias.
  • Avoid alcohol and other CNS depressants.

Special Considerations

Black Box Warnings:

  • Potential for dependence, withdrawal seizures if discontinued abruptly.

Genetic Factors: N/A

Lab Test Interference: May alter liver function tests, blood counts.

Overdose Management

Signs/Symptoms: Respiratory depression, ataxia, altered mental status, coma.

Treatment: Supportive care, airway management, activated charcoal if recent ingestion, hemodialysis in severe cases.

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.