Sounds like 'fee-noh-barb-a-tone'

Key points about phenobarbitone

  • Phenobarbitone is used to treat epilepsy.
  • Phenobarbitone is also called phenobarbital.
  • Find out how to take it safely and possible side effects.
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Phenobarbitone is used to treat epilepsy by preventing seizures. Phenobarbitone blocks certain kinds of nerve activity and in this way reduces seizures. Read more about epilepsy. 


March 2024: The funded brands of phenobarbitone 15mg and 30mg tablets are changing

The factory that made the PSM brand of phenobarbitone tablets has closed down.
From July 2023, phenobarbitone 30mg tablets were changed from PSM brand to Noumed brand.
From Feb 2024, all phenobarbitone tablets can only be supplied 1 month at a time because they are controlled drugs.

From March 2024 people taking the 15mg tablets will need to begin the brand change process from PSM to Noumed brand. You will need to visit your doctor twice, 1 month before and 1 month after you start taking the new brand. You won't need to pay for these visits to your doctor. You will also need blood tests.

Find out more about Phenobarbitone 15mg and 30mg tablets: brand change(external link).

In Aotearoa New Zealand, phenobarbitone is available as tablets (15 mg and 30 mg) and can be given as an injection in the hospital. It can also be made into a syrup by your pharmacy – note they will need time to prepare this.

  • Timing: Phenobarbitone is usually taken once a day, at bedtime. Take your dose at about the same time each evening. You can take phenobarbitone with or without food. Swallow your tablets with a glass of water. 
  • Missed dose: If you forget to take your dose, take it as soon as you remember. But if it's nearly time for your next dose, take the next dose at the right time. Don't take extra doses to make up for a forgotten dose. If you're not sure what to do, ask your healthcare provider.
  • Keep taking phenobarbitone every evening: See tips to help you remember to take your medicines regularly. It may take a few weeks before you notice the full benefits of phenobarbitone. Don't stop taking phenobarbitone suddenly; talk to your doctor or nurse before stopping.

Here are some things to know when you're taking phenobarbitone. Other things may be important as well, so ask your healthcare provider what you should know about.

Taking other medicines and supplements

Phenobarbitone interacts with many other medicines, herbal supplements and rongoā Māori, so check with your doctor or pharmacist before starting phenobarbitone and before starting any new products.

Phenobarbitone may affect your ability to drive

Phenobarbitone can impair your ability to do some tasks, eg, driving or using machines. Alcohol makes these effects worse. Discuss this with your healthcare provider.

Tell your healthcare providers

Make sure you tell anyone providing you with health, dental or medical care that you're taking phenobarbitone.

Pregnancy and breastfeeding

Phenobarbitone should not be taken during pregnancy or breastfeeding. If you're pregnant, planning a pregnancy or breastfeeding, let your doctor know straight away, they will advise you about other medicines you can take instead. Don’t stop taking phenobarbitone without talking to your healthcare provider first, it will need to be stopped gradually. If you are of childbearing age, your doctor will be able to advise you about the most effective contraception options while you're taking phenobarbitone – note that some types of contraception won't work as well while you're taking it.

Like all medicines, phenobarbitone can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine

Side effects What should I do?
  • Feeling sleepy, drowsy or tired
  • Feeling dizzy
  • Forgetfulness
  • Try getting up or moving slowly – you're at increased risk of falls.
  • If you begin to feel faint, sit or lie down until the feeling passes.
  • Avoid driving until you know how this medicine affects you.
  • Don't drink alcohol.
  • Tell your doctor if this continues.
  • Skin rash, skin peeling or blisters
  • Stop taking and see your doctor immediately.
  • Suicidal thoughts, anxiety, depression 
  • Tell your doctor.
  • Sore mouth, sore throat, mouth ulcers, easy bruising, nosebleeds, bleeding gums, shortness of breath, fever or infection.
  • Tell your doctor immediately or ring Healthline 0800 611 116.
  • Signs of problems with your liver such as severe tummy pain, yellowing of the eyes and skin, dark urine.
  • Tell your doctor immediately or ring Healthline 0800 611 116.

Read more about medicines and side effects and reporting a reaction that you think might be a side effect.

Phenobarbital(external link) NZ Formulary Patient Information


Phenobarbitone factsheet [PDF, 66 KB] Pharmac, NZ
5 questions to ask about your medications(external link) Health Quality and Safety Commission, NZ English(external link), te reo Māori(external link)


  1. Phenobarbital(external link) New Zealand Formulary


5 questions to ask about your medications

5 questions to ask about your medications

Health Quality and Safety Commission, NZ, 2019 English, te reo Māori


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Credits: Healthify He Puna Waiora Pharmacists. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland.

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