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Active substance(s): PHENOBARBITAL

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Read all of this leaflet carefully before you start taking this medicine.
o Keep this leaflet. You may need to read it again.
o If you have further questions, please ask your doctor or your pharmacist.
o This medicine has been prescribed for you. Do not pass it on to others. It may harm them,
even if their symptoms are the same as yours.
o If any side effects get serious, or if you notice any side effect not listed in this leaflet, please
tell your doctor or pharmacist.

1. What Phenobarbital is and what it is used for
2. Before you take Phenobarbital
3. How to take Phenobarbital
4. Possible side effects
5. How to store Phenobarbital
6. Further information

Phenobarbital belongs to a group of medicines known as barbiturates.
Phenobarbital is used to treat epilepsy.
In an epileptic fit, excessive electrical activity builds up in the brain. Phenobarbital works by
neutralising this excessive electrical activity.

Do NOT take Phenobarbital if you:
o are allergic (hypersensitive) to phenobarbital, other barbiturates or any of the other ingredients in
this medicine (see section 6)
o suffer from a rare condition called porphyria (disorder of the red blood pigment haemoglobin that
is passed down through families)
o have long-term kidney or liver problems
o severe breathing difficulty

Take special care with Phenobarbital
A small number of people being treated with anti-epileptics such as Phenobarbital have had thoughts
of harming or killing themselves. If at any time you have these thoughts, contact your doctor
Tell your doctor or pharmacist of any medical problems you may have, or have previously had,
especially if:


the person taking these tablets is elderly, young, debilitated or suffering from senile dementia
you have a history of drug abuse or alcoholism
you have kidney or liver problems
you have breathing difficulties
you suffer from severe or long term pain

Taking other medicines
Please tell your doctor or pharmacist if you are taking or have recently taken any other medicines,
including medicines obtained without a prescription. It is especially important for your doctor to know
if you are already being treated with any of the following medicines:
o Anticoagulants, medicines used to thin the blood (e.g. warfarin)
o Medicines to treat mental illness (e.g. chlorpromazipine, haloperidol, thioridazine, aripiprazole and
o Medicines to treat infections (antibiotics):
o Chloramphenicol, used to treat eye and ear infections
o Doxycycline, used to treat infections caused by a wide range of bacteria
o Griseofulvin, used to treat fungal infections of the skin
o Metronidazole, used to treat infections of the urinary, genital and digestive system
o Rifampicin, a drug used to treat tuberculosis
o Telithromycin, used to treat community acquired pneumonia
o Itraconazole, posaconazole, voriconazole - used to treat fungal infections
o Systemic steroids, including oral contraceptives (medicine used to prevent pregnancy) - may lead
to failure of medication
o Ciclosporin or tacrolimus used in organ and tissue transplants
o Other medicines used to treat epilepsy (e.g. phenytoin, lamotrigine, carbamazepine, sodium
valproate, oxcarbazepine, tiagabine, primadone, zonisamide, vigabatrin and ethosuximide)
o Medicines used to treat depression (e.g. mianserin, paroxetine)
o Medicines used to treat heart trouble (e.g. nifedipine, felodipine, verapamil, nimodipine, isradipine,
diltiazem, metoprolol, timolol and propranolol)
o Medicines used to help your breathing (e.g. theophylline, montelukast)
o Levothyroxine and liothyronine, used to treat disorders of the thyroid gland
o The herbal remedy St John’s wort (Hypericum perforatum) should not be taken at the same time as
this medicine. If you already take St John’s wort, consult your doctor before stopping the St John’s
wort preparation.
o Antiviral medicines used in the treatment of HIV (e.g. abacavir, amprenavir, darunavir, nelfinavir,
indinavir, saquinavir and lopinavir)
o Medicines used to treat heart problems (e.g. disopyramide, quinidine, eplerenone and digitoxin)

High doses of folic acid
Irinotecan or etopside (to treat some cancers)
Toremifene, used to treat breast cancer
Gestrinone, used for the treatment of endometriosis
Tibolone, used for hormone replacement therapy in post-menopausal women
Tropisetron and aprepitant, used to treat nausea and vomiting following chemotherapy
Methadone, used for severe pain and drug addiction
Memantine, used to treat dementia (condition causing gradual loss of brain function)

o Methylphenidate, to treat attention deficit disorder (syndrome characterised by learning and
behavioural problems)
o Sodium oxybate, to treat narcolepsy (sleep disorder causing recurrent episodes of sleep occurring
throughout the day)
o Vitamin D (requirements may be increased)
o Steroids such as hydrocortisone or prednisolone

Using Phenobarbital with food and drink
Do not drink alcohol while taking this medicine without first talking to your doctor.
Pregnancy and breast-feeding
If you are pregnant or planning to become pregnant you should speak to your doctor before taking
Phenobarbital. If you become pregnant while taking Phenobarbital your doctor will decide if you
should continue taking this medicine or whether another would be more suitable during pregnancy.
Do not stop taking phenobarbital until you have seen your doctor, as it is important to control fits.
If taken during pregnancy (particularly in the first 3 months and the last 3 months), Phenobarbital
may cause birth defects. It may also cause problems with bleeding in your baby when it is born.
However, your doctor may decide that it is very important that you continue taking Phenobarbital.
Your doctor will explain the risks to you.
Check with your doctor before taking folic acid supplements. Folic acid may interact with
Phenobarbitol tablets, your doctor may need to adjust your dose.
As Phenobarbital is released into breast milk, this may harm the baby and therefore, breast-feeding
is not advisable.
Driving and using machines
Phenobarbital may make you feel drowsy. Do not drive or operate machinery if you feel drowsy
when you start to take this medicine.
Important information about some of the ingredients of Phenobarbital
Phenobarbital contains lactose monohydrate. If you have been told by your doctor that you have an
intolerance to some sugars, contact your doctor before taking this medicinal product.
Phenobarbital 60mg Tablets contain the colour sunset yellow (E110). This may cause allergic-type
reactions including asthma. Allergy is more common in those people who are allergic to aspirin.
Blood and urine tests
If you are having blood or urine tests tell the doctor or nurse that you are taking Phenobarbital
Tablets as Phenobarbital may affect the results of these tests.
Swallow the tablets with a drink of water.

Always take Phenobarbital exactly as your doctor has told you. You should check with your doctor or
pharmacist if you are not sure.
The usual dose is 60mg -180mg daily, taken at night.
If this medicine is prescribed for a child make sure that the tablets are taken as stated on the
pharmacist’s label. The usual dose is 5mg-8mg per kg of bodyweight per day.
Your doctor may prescribe a lower dose.
If you take more Phenobarbital than you should
The symptoms of an overdose may include drowsiness, difficulty breathing, low blood pressure, low
body temperature (hypothermia), speech problems, jerky movements, jerky eye movements, loss of
inhibition, reduced reflex response and coma.
If you or anyone else has swallowed a lot of the tablets all together contact your nearest hospital
casualty department or doctor immediately.
If you forget to take Phenobarbital
If you forget to take a dose, take it as soon as you remember, then go on as before. Do not take a
double dose to make up for a forgotten dose.
If you stop taking Phenobarbital
Do not stop taking Phenobarbital unless your doctor tells you to. If you stop taking Phenobarbital
suddenly or before your doctor tells you to, there is an increased risk of seizures. You may develop
withdrawal effects such as sleeplessness, anxiety, tremor, dizziness, feeling sick, fits and delirium.
Always speak to your doctor or pharmacist.
Like all medicines Phenobarbital can cause side effects, although not everybody gets them.
If you experience any of the following contact your doctor IMMEDIATELY:
o Allergic reactions e.g. fever, swelling of the face, lips, tongue or throat, difficulty breathing or
swallowing, skin rashes.
o A yellowing of your skin or the whites of your eyes, which may be signs of hepatitis (inflammation
of the liver) or cholestasis (damaged bile system),
o potentially life-threatening skin rashes such as erythema multiforme (skin rash or skin lesions with
a pink/red ring and a pale centre which may be itchy, scaly or filled with fluid. The rash may appear
especially on the palms or soles of your feet), Sevens-Johnson syndrome (blistering or bleeding of the
skin around the lips, eyes, mouth, throat, nose or genitals and conjunctivitis (red and swollen eyes).
Rashes may progress to widespread blistering/peeling of the skin. Also flu-like symptoms and fever),

toxic epidermal necrolysis (severe blistering rash, peeling of the skin, raw exposed skin. Feeling
generally unwell, fever, chills and aching muscles). The highest risk of developing serious skin
reactions occurs within the first two weeks of treatment
You must not be re-started on Phenobarbital tablets at any time if you have developed StevensJohnson syndrome or toxic epidermal necrolysis with the use of Phenobarbital tablets.

Tell your doctor as soon as possible if you have any of the following side effects:
o Restlessness, difficulty in concentrating in the elderly, unusual excitement, depression, memory
impairment, hallucinations (seeing or hearing things that are not real).
o Hyperactivity, changes in behaviour in children, jerky movements, jerky eye movements,
drowsiness, lack of energy
o Hypotension - low blood pressure
o Difficulty breathing
o Changes in the amount or need to pass water
o Anaemia, altered numbers and types of blood cells. If you notice increased bruising, nosebleeds,
sore throats or infections, you should tell your doctor who may want to perform a blood test.
o Bone softening and bone disease
There have been reports of bone disorders including osteopenia and osteoporosis (thinning of the
bone) and fractures. Check with your doctor or pharmacist if you are on long-term antiepileptic
medication, have a history of osteoporosis, or take steroids.If any of the side effects get serious, or if
you notice any side effects not listed in this leaflet, please tell your doctor or pharmacist.
Reporting side effects
If you get any side effects, talk to your doctor or pharmacist. This includes any possible side effects
not listed in this leaflet. You can also report side effects directly via the Yellow Card Scheme at By reporting side effects you can help provide more information on
the safety of this medicine.

Do not use Phenobarbital after the expiry date stated on the pack. The expiry date refers to the last day
of that month.
Do not store above 25°C. Keep the container tightly closed. Store in the original container. Medicines
should not be disposed of via wastewater or household waste. Ask your pharmacist how to dispose of
medicines no longer required. These measures will help to protect the environment.
What Phenobarbital contains
The active substance is phenobarbital.
The other ingredients are maize starch, lactose monohydrate, sodium lauryl suphate, sodium starch
glycolate, magnesium stearate and stearic acid.
The 60mg tablets contain the colour sunset yellow E110.

What Phenobarbital looks like and the contents of the pack
Phenobarbital 30mg Tablets are white, circular tablets. Each tablet contains 30mg of phenobarbital,
the active ingredient.
Phenobarbital 60mg Tablets are pale, orange, circular tablets. Each tablet contains 60mg of
phenobarbital, the active ingredient.
The tablets are available in packs of 28 and 1,000 tablets. Not all pack sizes may be marketed.
Marketing Authorisation Holder
Relonchem Limited, Cheshire House, Gorsey Lane, Widnes, WA8 0RP, UK.
PL 20395/0112 and PL 20395/0113
This leaflet was last revised in

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Source: Medicines and Healthcare Products Regulatory Agency

Disclaimer: Every effort has been made to ensure that the information provided here is accurate, up-to-date and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. This information has been compiled for use by healthcare practitioners and consumers in the United States. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate that the drug or combination is safe, effective or appropriate for any given patient. If you have questions about the substances you are taking, check with your doctor, nurse or pharmacist.