> Western Medicines > Phenytoin


Used for:Treatment and prevention of seizures and epilepsy
Chinese name:

What is Phenytoin for?

Phenytoin is an anticonvulsant medicine commonly used for treating a wide variety of seizures and epilepsy. It can be given while in the hospital to prevent seizures during or following neurosurgery or severe head injury.

How to use it?

Phenytoin can be taken by mouth as capsules or oral suspension, and by injection.


The usual adult dosage of phenytoin is 100 mg by mouth 3 times per day. You may require a higher dosage to treat your seizure condition. Your doctor may adjust your phenytoin dose based on your blood level of phenytoin.

What are the side effects of Phenytoin?

Major side effects of Phenytoin are reduced bone mineral (phenytoin decreases calcium and vitamin D levels) density, gingival hyperplasia, skin rash, and increased hair growth.

Who should not take Phenytoin?

  • People who are allergic to phenytoin
  • People with history of acute liver failure

Pharmacist Tips:

  • Phenytoin leads to sedation and avoids activities that require mental alertness.
  • Report to physician or pharmacist if there is suicidal ideation or decreased heart rate.
  • Do not consume alcohol while on this medication.
  • Avoid abrupt discontinuation to limit withdrawal effects.

Common dosing schedule:
Phenytoin can be taken with or without food.


This schedule is for reference only, adjustments may be made according to individual needs.


Some common medications Phenytoin may interact with:

Please notify your doctor or pharmacist if you are taking the above medication, dosage adjustments might be needed.

Where to buy Phenytoin in Hong Kong?

In Hong Kong, Phenytoin is a prescription only medicine, and requires a prescription from a doctor to be purchased in a pharmacy. It can also be obtained from doctors. To find a pharmacy near you, refer to the list of pharmacies (“Authorized Sellers of Poisons”) from the Hong Kong Department of Health.


For more information about drug names and ingredients, you can visit Hong Kong’s Drug Office at https://www.drugoffice.gov.hk

Need more information?

For detailed information about the use of Phenytoin in children, pregnancy and breastfeeding, and for questions about drug interactions, please check with your pharmacist or doctor.

Disclaimer: our goal is to provide you with the most relevant drug information and common dosage for Hong Kong. This information does not constitute medical advice. For specific treatment recommendations and advice, always discuss with your doctor or pharmacist, and follow the instructions included with your specific medicine.

Brands in Hong Kong
Available dosage
  • 30mg (Extended-Release Capsules)
  • 250mg/5ml (Injections)
  • 100mg (Tablets)
Drug class
Sub class
Sodium Channel Blockers
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