Grand mal and temporal epilepsy; migraine; arrhythmia; skeletal muscle relaxant; trigeminal neuralgia.
150-300mg daily in single or divided doses [max.600mg]. Children: 5-8mg/kg daily in 1 or 2 doses to be taken after meals. Status epilepticus, acute symptomatic seizures associated with trauma or neurosurgery.By slow intravenous injection or infusion [with blood-pressure and ECG monitoring], neonate, initially 20 mg/kg as a loading dose then 2.5–5 mg/kg twice daily. Child 1 month–12 years initially 20 mg/kg as a loading dose then 2.5–5 mg/kg twice daily, Child 12–18 years initially 20 mg/kg as a loading dose then up to 100 mg 3–4 times daily.
Mode of action
Brands containing this Ingredient
Phenytoin, by Biodeal
Phenytoin, by Allied
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Mode of Action
The mechanism of action is not fully known. It is thought to involve stabilization of neuronal membranes at the cell body, axon, and synapse and limitation of the spread of neuronal or seizure activity. It decreases sodium and calcium ion influx by prolonging voltage-dependent channel inactivation time during generation of nerve impulses.
It has a low therapeutic index hence it requires therapeutic drug monitoring; severe myocardial insufficiency; to be withdrawn or substituted gradually; administration of vitamin K to mothers during delivery and infant after delivery.
Drug interactions: Drugs that increase its plasma concentration because of inhibition of its metabolism resulting in increased effects and / or toxicity include: aspirin, phenylbutazone, amiodarone, chloramphenicol, isoniazid, metronidazole trimethoprim, cotrimoxazole, fluoxetine, tolbutamide, fluconazole, nifedipine, diltiazem, disulfirum, cimetidine, and sulphinpyrazone. Drugs that reduce its plasma concentration or effects include: anti-psychotics, folic acid, and rifampicin.
Others: Antagonism with anti-depressants; anti-folate effect enhanced by use of anti-folate drugs like pyrimethamine and methotrexate.