Phenytoin
Also sold as: Epanutin, Dilantin
Usual adult dose
Dose is set by your doctor, often 200 mg to 400 mg a day, sometimes guided by blood levels. Take it at the same time each day and do not stop it suddenly.
Your doctor may give you a different dose. Children's doses depend on weight.
Side effects
Common
- drowsiness
- unsteady walking
- swollen or overgrown gums
- extra body hair
- acne
Serious — get help
Stop taking it and see a doctor straight away if you notice:
- severe skin rash with blisters or peeling
- double vision with severe unsteadiness
- yellow eyes or skin
- fever with sore throat
- unusual bleeding
Do not take it, or take care, if
- Pregnancy (can harm the baby — plan with your doctor)
- Very slow heartbeat or heart block (injection)
- Liver disease (use with caution)
- Past severe skin rash with this medicine
Interactions
Medicines that can react with this one.
Serious5 medicinesDo not take these together unless your doctor says so.
- Daclatasvir
Phenytoin strongly lowers daclatasvir levels; do not combine.
- Ethinylestradiol + Levonorgestrel
Phenytoin makes the contraceptive pill less effective; use another method.
- Isoniazid
Isoniazid raises phenytoin levels and can cause toxicity.
- Levonorgestrel
Phenytoin makes levonorgestrel less effective; ask a doctor about a double dose or a copper IUD.
- Warfarin
Phenytoin changes warfarin levels in both directions; INR must be checked closely.
Moderate11 medicinesTake together only with care. Ask your doctor or pharmacist.
- Aminophylline
Phenytoin lowers theophylline levels, and theophylline can lower phenytoin levels.
- Chloramphenicol
Raises phenytoin levels; watch for unsteadiness or drowsiness.
- Clonazepam
Phenytoin lowers clonazepam levels; seizure control should be watched.
- Co-trimoxazole
Raises phenytoin levels; watch for unsteadiness or drowsiness.
Minor1 medicineUsually not a problem, but tell your doctor.
- Pyridoxine
High doses of pyridoxine can lower phenytoin levels.