Phenytoin is used to treat epilepsy. Find out how to take it safely and possible side effects. Phenytoin is also called Dilantin.
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What is phenytoin?
Phenytoin is used to treat epilepsy by preventing seizures. It works by stabilising the electrical activity in your brain and in this way reduces seizures. Read more about epilepsy.
In New Zealand phenytoin is available as:
- chewable tablets (50 mg)
- capsules (30 mg and 100 mg)
- liquid.
Dose of phenytoin
- The dose of phenytoin will be different for different people.
- Your doctor will start you on a low dose, and increase your dose slowly over a few weeks.
- Phenytoin is usually taken once or two times a day.
- Always take your phenytoin exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much phenytoin to take, how often to take it, and any special instructions.
How to take phenytoin
- Phenytoin is best taken with or after food.
- Take your doses at the same times each day, usually once or two times a day.
- For doses that are taken two times a day, take it once in the morning and once in the evening. Ideally, these times are 10–12 hours apart, for example, some time between 7 and 8 am and between 7 and 8 pm.
- Phenytoin is available as chewable tablets, capsules and liquid.
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- Limit drinking alcohol while you are taking phenytoin. It can increase your chance of side effects such as dizziness.
- If you forget to take your dose, take it as soon as you remember. But, if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.
- Keep taking phenytoin regularly every day (see tips to help you remember to take your medicines regularly). Do not stop taking phenytoin suddenly as this can cause problems; speak to your doctor or nurse before stopping.
Precautions before taking phenytoin
- Are you pregnant, planning a pregnancy or breastfeeding?
- Do you have liver problems?
- Are you of Han Chinese or Thai origin?
- Are you are taking or using any other medicines including birth control tablets? This includes any medicines you are using that are available to buy from a pharmacy, supermarket or natural health store without a prescription.
If so, it’s important that you tell your doctor or pharmacist before you start taking phenytoin. Sometimes a medicine isn’t suitable for a person with certain conditions or it can only be used with extra care.
What are the side effects of phenytoin?
Like all medicines, phenytoin can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.
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Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product |
Interactions
Phenytoin interacts with some other medications and herbal supplements, so check with your doctor or pharmacist before starting phenytoin or before starting any new medicines. Do not take indigestion medication (antacids) within 2 hours of taking phenytoin. Some contraceptives may not work as well while you are taking phenytoin, and for 4 weeks after stopping. Discuss
with your doctor or pharmacist.
Learn more about phenytoin
Phenytoin New Zealand Formulary
Phenytoin (for children) New Zealand Formulary
Dilantin Medsafe Consumer Information Sheet
Epilepsy/seizures and driving NZTA, 2018
References
- Phenytoin New Zealand Formulary
Additional resources for healthcare professionals
Prescribing issues associated with anticonvulsant medications for epilepsy BPAC, NZ, 2009
Practical considerations for therapeutic drug monitoring BPAC, NZ, 2009