Phenytoin

Please note: these are basic guidelines, refer to your doctor for a professional medical opinion.

Popular brand names:

Epanutin

Drug group:

Anticonvulsant drug

Prescription needed?

Yes

What does it do?

Phenytoin reduces abnormal electrical activity in the brain and is used in the treatment of:

• Epilepsy - it decreases the likelihood of convulsions
• Certain pain disorders - migraine, trigeminal neuralgia
• Certain abnormal heart rhythms

How should it be used?

• You should try stick to the same brand of phenytoin
• Phenytoin should be taken with food or plenty of water
• Folic acid and vitamin D deficiency may occur - eat a balanced diet containing fresh, green vegetables and dairy products
• Many drugs can interfere with phenytoin, discuss with your doctor or pharmacist

What is the typical dosage?

Your doctor will recommend a dosage tailored to your need, but typically:

• Adults: 200–500mg daily, usually as a single dose
• Children: dose calculated according to age and weight, given once or twice daily
• The dose may be adjusted according to blood levels of the drug - a small increase in the dose can cause a disproportionately high drug level in the blood

How quickly will it start to work?

Full anticonvulsant effect may take 7–10 days     
               

How long will the effects last?

24 hours

When should I stop using it?

Do not stop the drug without consulting your doctor            
   

Is it safe for prolonged use?

Long-term use of the drug can cause: disrupted control of diabetes, blood abnormalities, adverse effects on skin, gums, and bones. You may need regular blood tests to monitor blood levels of the drug, as well as the blood cells and blood chemistry.

What are the possible side effects?

Phenytoin’s side effects usually only appear after prolonged use.

The following have been reported:

• More common: dizziness, headache, nausea, vomiting, insomnia
• Less common: increased body hair, overgrowth of the gums
• Report to your doctor before taking your next dose if you experience: confusion, unsteadiness, rash, fever, sore throat, mouth ulcers

What other considerations are important?

Dosage may be adjusted by your doctor under certain conditions.

• Certain health problems: liver/kidney problems, diabetes, porphyria
• Other medicines: Oral contraceptives, antidepressants, antipsychotics, St John’s wort, mefloquine/chloroquine, warfarin
• Pregnancy and breast-feeding: The drug is avoided in pregnancy as it may be harmful to the foetus, normal doses are unlikely to affect the breastfed baby
• Children: Reduced dose necessary, increased risk of gum and body hair changes
• Over 60: Reduced dose may be necessary
• Driving and hazardous work: Caution, your underlying condition or the drug may make such activities inadvisable
• Alcohol: Avoid, enhanced sedative effects