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Phenytoin (Dilantin, Di-Phen, Diphenylan, Phenytex){oral} Fosphenytoin (Cerebyx){intravenous}

Category:

  • Miscellaneous

Description:

  • Anticonvulsive

Indications:

  • Generalized tonic-clonic seizures, simple or complex seizures, status epilepticus

  • Nonepileptic seizures associated with Reye’s syndrome or after head trauma

  • Fosphenytoin- substitute for oral phenytoin when PO administration not feasible; migraines, Bell’s palsy, ventricular dysrhythmias,

  • Diabetic neuropathy pain (non FDA approved)

Contraindications:

  • Bradycardia, 2nd and 3rd degree AV block, Stokes-Adams syndrome

  • Sinoatrial block

Precautions:

  • Pregnancy category D (risk of congenital defects increased 2-3 times); compatible with breast feeding

  • Hepatic disease

  • Renal disease

  • Diabetes mellitus

Adverse Reactions (Side Effects):

  • CNS: ataxia, confusion, dizziness, drowsiness, fatigue, headache, insomnia, nystagmus, paresthesias, psychiatric changes, slurred speech

  • CV: CV collapse (when drug administered too rapidly IV), hypotension, ventricular fibrillation

  • EENT: blurred vision, diplopia, gingival hyperplasia

  • GI: anorexia, constipation, hepatitis, jaundice, nausea, vomiting, weight loss

  • GU: nephritis

  • MEME: agranulocytosis, aplastic anemia, leukopenia, lymphadenopathy, megaloblastic anemia, thrombocytopenia

  • METAB: hyperglycemia

  • SKIN: alopecia, hirsutism, lupus erythematosus, rash, Stevens-Johnson syndrome  

Dosage:

NOTE: Fosphenytoin 75mg equivalent to 50mg phenytoin, after administration; the dose of IV fosphenytoin is expressed as phenytoin equivalents (PE) to avoid the need to perform molecular weight-based adjustments when converting between fosphenytoin and phenytoin doses.

  • Adult: Phenytoin 

    • Seizures: IV loading dose 15-20 mg/kg based on recent dosing history and serum levels, followed by 100mg PO or IV every 6-8 hours; PO loading dose 1g divided 400mg, 300mg, 300mg given every 2 hours; if load not necessary, may give 100mg 3 times daily, follow levels; maintenance dose: 300mg daily or 5-6 mg/kg/day in divided doses; once dosage established may use extended capsules and dose daily

    • Neuritic pain: PO 200-400mg daily

    • Fosphenytoin:

    • Status epilepticus: IV 15-20mg PE/kg loading dose administered at 100-150mg PE/minute

    • Nonemergent and maintenance dosing: IM/IV 10-20mg PE/kg loading dose administered at a rate < or = 150mg PE/minute: maintenance 4-6mg PE/kg/day

  • Child: Phenytoin

    • Seizures: IV loading dose 15-20 mg/kg in divided doses of 5-10 mg/kg; PO 5 mg/kg/day in 2-3divided doses to max 300mg daily; daily maintenance dose 4-8 mg/kg

Special considerations:

  • Therapeutic range 10-20 mcg/ml; nystagmus appears at 20 mcg/ml, ataxia at 30 mcg/ml, dysarthria and lethargy at levels above 40 mcg/ml; lethal dose 2-5g

  • Pro-drug: fosphenytoin rapidly converted to phenytoin in vivo: minimal activity before conversion; water soluble, thus more suitable for parenteral applications: doesn’t require cardiac monitoring; can be administered at faster rate; no IV filter required; compatible with both saline and dextrose mixtures; requires refrigeration

 


The information contained here is an abbreviated summary. For more detailed and complete information, consult the manufacturer's product information sheets or standard textbooks

Source: Operational Medicine 2001,  Health Care in Military Settings, NAVMED P-5139, May 1, 2001, Bureau of Medicine and Surgery, Department of the Navy, 2300 E Street NW, Washington, D.C., 20372-5300

This information is provided by The Brookside Associates.  The Brookside Associates, LLC. is a private organization, not affiliated with any governmental agency. The opinions presented here are those of the author and do not necessarily represent the opinions of the Brookside Associates or the Department of Defense. The presence of any advertising on these pages does not constitute an endorsement of that product or service by either the US Department of Defense or the Brookside Associates. All material presented here is unclassified.

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