Composition
Cap/Tab 100 mg: Phenytoin sodium 100 mg. Susp 30 mg: Per 5 -: Phenytoin sodium 30 mg. Susp 125 mg: Per 5 -: Phenytoin sodium 125 mg. Inj 250 mg: Per -: Phenytoin sodium 50 mg: 5 - (250 mg)
Indications & Dosage
Tonic-clonic seizures, Focal seizures: Children 1 month-11 yrs: Initially 1.5-2.5 mg/kg twice daily, then adjusted according to response to 2.5-5 mg/kg twice daily (max. per dose 7.5 mg/kg twice daily), dose also adjusted according to plasma phenytoin concentration; max. 300 mg per day; 12-17 years: Initially 75-150 mg twice daily, then adjusted according to response to 150-200 mg twice daily (max. per dose 300 mg twice daily), dose also adjusted according to plasma-phenytoin concentration. Tonic-clonic seizures, Focal seizures, Prevention and treatment of seizures during or following neurosurgery or severe head injury: Adult: Initially 3-4 mg/kg daily, alternatively 150-300 mg once daily or in 2 divided doses; usual maintenance 200-500 mg daily, to be taken preferably with or after food, dose to be increased gradually as necessary (with plasma phenytoin concentration monitoring), exceptionally, higher doses may be used if needed. Prevention and treatment of seizures during or following neuro surgery or severe head injury: Children: Initially 2.5 mg/kg twice daily, then adjusted according to response to 4-8 mg/kg daily, dose also adjusted according to plasma-phenytoin concentration; max. 300 mg per day. Status epilepticus, Acute symptomatic seizures associated with head trauma or neurosurgery: BY SLOW IV INJ, OR BY IV INF: Adult: Loading dose 20 mg/kg (max. per dose 2 g), then (by IV INF or by slow IV injection or oral) maintenance 100 mg every 6-8 hours adjusted according to plasma-concentration monitoring. Children 1 month-11 yrs: Loading dose 20 mg/kg, then (by slow IV injection or by IV INF) 2.5-5 mg/kg twice daily; 12-17 yrs: Loading dose 20 mg/kg, then (by IV INF or by slow IV injection) up to 100 mg 3-4 times a day.
Administration
Administered by direct IV injection into a large vein. The rate of IV injection should not exceed 50 mg/min in adults or 1-3 mg/kg/min in neonates. Following IV injection, NaCI 0.9% should be injected through the same needle or catheter to reduce irritation.
Compatibility
Stable in dextrose 5%, NaCI 0.9%, fat emulsion 10% IV.
Stability
Phenytoin is stable as long as it remains free of haziness and precipitation. If refrigerated or frozen, a precipitation may form, but it dissolves on standing at room temperature.
Contraindications
Acute porphyria, sinus bradycardia, sino-atrial block, and second- and third-degree heart block, Stokes-Adams syndrome, moderate or severe renal impairment, severe hepatic impairment
Precautions
Hepatic dysfunction. Withdraw drug gradually. With intravenous use: Heart failure, hypotension, injection solutions alkaline (irritant to tissues), respiratory depression, resuscitation facilities must be available. Consider vitamin D supplementation in patients who are immobilised for long periods or who have inadequate sun exposure or dietary intake of calcium. Intramuscular phenytoin should not be used (absorption is slow and erratic).
Interactions
: Coumarin anticoagulants, doxycycline, isoniazid, chloramphenicol, oral contraceptives.
Pregnancy
Avoid unless the potential benefit outweighs the risk.
Lactation
Contraindicated, avoid
Side Effects
Aggression, anxiety, ataxia, blurred vision, changes in appetite, confusion, diplopia, dizziness, drowsiness, dysarthria, gait disturbance, irritability, malaise, nausea, suicidal behavior, suicidal ideation, vertigo, weight increase, back pain