Phenobarbitone

Medication Information Leaflet

What is this medication for?

Phenobarbitone is used to control some types of seizures (commonly known as fits). 

How should I take/use this medication?

Follow the instructions on your medication label and take the medication as prescribed by your doctor.

If you are using oral syrup, shake the bottle well before using. Use a medicine spoon or graduated syringe provided to measure your medication. Do not use household spoons as they may not be accurate. 

If you are taking the tablets, swallow the tablets with a glass of water. If you are unable to swallow the tablet, you may crush it and add it to a small amount of food (i.e yoghurt, ice-cream, syrup) before administering. You can take this medication with or without food. You can take it with food if you experience stomach upset. 

You should continue to take your medication regularly as instructed by your doctor even if you feel well. Stopping your medication without informing your healthcare professional may cause your condition to worsen quickly. 

Do not stop taking or adjust the dose of this medication without consulting your healthcare professional. 

What should I do if I forget to take/use this medication?

If you miss a dose, take the missed dose as soon as you remember. If it is almost time for your next dose, take only the usual dose. Do not double your dose or use extra medication to make up for the missed dose. 

What precautions should I take?

Inform your healthcare professional if you have the following medical conditions before starting on Phenobarbitone:
  • Liver, kidney or heart problems
  • Severe breathing difficulties
  • Porphyria (a genetic or inherited disorder of the red blood pigment haemoglobin)
  • Anemia

For women: Tell your doctor if you are pregnant and/or breastfeeding, your doctor would have discussed the potential benefits and side effects with continuing/starting this medication but should you have further questions or concerns, do consult your doctor.

Consult your healthcare professional immediately if your seizures get worse or become different after you start on this medication. 

Be careful when driving or operating machinery as this medication may cause drowsiness. 

What are some common side-effects of this medication?

Like all medicines, this medication may cause some possible side effects but not everyone experiences them. Consult your healthcare professional if any of the side effects lasts more than a few days or become severe and bothersome.

The common side effects of Phenobarbitone include:
  • Dizziness
    • Get up slowly from sitting or lying down position
  • Drowsiness or double vision
    • Avoid driving or engaging in activities that requires concentration
  • Constipation
    • Drink more water, eat more high-fibre foods, and exercise regularly
  • Nausea, vomiting, stomach upset
    • Take the medication with or after food to reduce nausea and vomiting
    • Avoid food that is too rich, spicy or has strong smells
    • Eat small but frequent meals to reduce bloating after a meal
  • Headache
    • Take Paracetamol if needed to relieve headache
  • Difficulty sleeping, hallucinations (seeing or hearing things that are not present), vivid dreams
  • Feeling tired and restless. Some patients may experience excitement. 
  • Weakened bones
    • Your doctor may prescribe calcium and vitamin D supplements for you

What are some rare but serious side-effects that I need to seek medical advice immediately?

The symptoms of a drug allergy include one or more of the following:
  • Swollen face / eyes/ lips / tongue
  • Difficulty in breathing
  • Itchy skin rashes over your whole body
If you experience any of these symptoms, you should stop your medication and see your healthcare professional immediately.

If the following serious side effects happen, you should consult your healthcare professional immediately:
  • Blistering, peeling, red skin rash due to Stevens-Johnson syndrome (SJS) or Toxic Epidermal Necrolysis (TEN)
    • SJS and TEN are rare and serious skin reactions. Symptoms include face swelling, blisters on skin, skin rashes that spread within hours to days. It usually occurs within the first few months (monitor closely for the first 3 months) of treatment. 
    • As SJS and TEN progress rapidly, please consult your healthcare professional if you show the first sign of a rash.
  • Unexplained bleeding or bruising
  • Difficulty in breathing
  • Liver problems: Dark-coloured urine or light-coloured stools, yellowing of your eyes or skin, severe loss of appetite, stomach pain, nausea, or vomiting that does not go away

In rare cases, this medication may cause the following changes to a person’s mental condition, especially in the first few weeks of treatment or during dose changes:
 
  • Worsening agitation, restlessness, violent behaviour
  • New or worsening thoughts of harming yourself or ending your life
  • Other changes in mood or behaviour
 
Please inform your doctor as soon as possible, or for your family or caregiver to inform your doctor if you are unable to seek treatment on your own. 
 
Do not stop taking this medication on your own without discussing with your doctor. 
 
It is important to note that your doctor has prescribed this medication as he/ she feels you will benefit more from taking this medication over the possible side effects that it may cause, which have a low chance of occurring. Most people take this medication without any such problems.

What food or medication should I avoid when I take this medication?

Avoid drinking alcohol while taking this medication as it can cause excessive drowsiness. 

Phenobarbitone can decrease the effectiveness of medications that prevent pregnancy. Check with your doctor about additional or other methods of birth control. 

How should I store this medication?

Store in a cool and dry place, away from direct sunlight. Keep this medication away from children.

How should I throw away this medication safely?

Pack this medication into a black trash bag and seal it tightly before throwing it into the rubbish chute or bin.




Disclaimers
If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.


This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.


Last updated on Aug 2021


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Phenobarbitone

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