Phenobarbital is used on its own or together with other medicines to treat epilepsy (also known as fits or seizures).
Take Phenobarbital exactly as directed by your doctor or according to the instructions on the label. Do not take more or less than instructed by your doctor.
You may take Phenobarbital with or without food, preferably at night.
Phenobarbital must be taken regularly for it to be effective. Continue taking Phenobarbital even when you feel better. Phenobarbital is not a cure and you may need to take it long-term to keep your seizures under control. Do not stop taking Phenobarbital unless instructed by your doctor as stopping it suddenly may worsen your condition.
Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and return to your normal dosing schedule.
DO NOT double a dose under any circumstances.
If you often forget to take your medicine, let your doctor and pharmacist know.
Alert your doctor if you have the following:
- history of porphyria (an inherited disorder that may cause skin or nerve problems)
- severe breathing difficulties
- liver disease
as Phenobarbital may not be suitable for you.
Inform your doctor if you have the following:
- suffer from long time pain
- kidney disease
Let your doctor know if you are pregnant or breastfeeding.
Phenobarbital may cause drowsiness, tiredness and giddiness. If affected, do not drive or take part in any activity in which you need to be alert. Initially, the drowsiness effect may be carried over to the next morning.
Other side effects include any of the following: headache, nausea, vomiting, constipation, excitability and problems with memory and judgement.
Some side effects may be serious, although they are not common. Alert your doctor quickly if you experience:
- rashes with peeling of the skin or blistering of the lips, mouth or eyes accompanied by fever
- confusion and hallucinations (seeing, hearing or feeling things that are not existent)
- unusual changes in mood or behaviour (being too depressed, agitated, or having thoughts of self-harm)
- breathing difficulties
- extensive or unusual bleeding or bruising
- mouth ulcers or persistent fever or sore throat
Inform your doctor if any of these side effects do not go away or are severe, or if you experience other side effects.
Inform your doctor and pharmacist if you are taking any of these medicines:
- other epilepsy medicines e.g. phenytoin, valproate
- blood-thinning medicines e.g. warfarin, dicumarol
- birth control pills e.g. ethinylestradiol, levonorgestrel
- medicines to treat bacterial infections e.g. chloramphenicol, doxycyline, metronidazole
- medicines to treat fungal infections e.g. griseofulvin
- medicines to treat mood disorders e.g. chlorpromazine, thioridazine
- medicines to treat viral infections e.g. abacavir, saquinavir, nelfinavir
- medicines for high blood pressure or heart disease e.g. felodipine, digitoxin
- medicines used in organ transplant or certain immune disorders e.g. ciclosporin
- anti-inflammatory medicine e.g. prednisolone
- folic acid supplements
This list does not include all medicines that may interact with Phenobarbital.
Always notify your doctor and pharmacist if you are taking any other medicines, including herbal tonics such as traditional Chinese medicine, supplements and medicines that you buy without a prescription.
Avoid alcohol and St. John's wort.
Store in a cool, dry place away from the reach of children.
Medicines must not be used past the expiry date.