Mechanism of Action: Phenytoin acts by blocking voltage dependent sodium channels and thus prevents seizures to occur. Its anticonvulsant activity is through blocking sustained high frequency repetitive firing of the action potentials. Its primary site of action appears to be in the motor cortex where it prevents the spread of the seizure activity.
Clinical Uses: Phenytoin is widely used in medicine for conditions like:
- Complex-partial seizures
- Generalized tonic clonic seizures
- Status epilepticus
- As an antiarrythmic drug to control an abnormal heart beat.
- Arrythmias caused by digoxin toxicity.
- Second choice for trigeminal neuralgia.
- Phenytoin has a narrow therapeutic index and needs monitoring of plasma concentration.
- Phenytoin may interact with other drugs and it is important to inform the doctor and the pharmacist of any other medicines the patient may be taking before using phenytoin.
- Do not use this drug if the patient is pregnant as it may cause severe fetal damage.
- If given by intramuscular injection can lead to skin necrosis and local tissue destruction.
- Before starting this drug it is important to get basal liver function tests and a history of any liver disease, diabetes, history of depression or suicidal thoughts, as well as any other underlying diseases like porphyria.
- It is not considered to be safe to consume large amounts of alcohol while taking phenytoin.
- Difficult falling asleep or staying asleep.
- Nausea and vomiting
- Severe hypotension and cardiac arrthymias
- Uncontrollable eye movements
- Uncoordinated body movements.
- Coarsening of facial features.
- Overgrowth of gums and enlargement of lips.
- Unwanted hair growth
- Serious effects like jaundice and unusual bleeding etc.
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