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Phenobarbital for epilepsy

You need to take phenobarbital regularly every day. Take your dose at bedtime.

Phenobarbital may cause you to feel drowsy and unsteady. This often settles down as your body adjusts to the new medicine.

Do not drink alcohol.

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About phenobarbital

Tipo de medicamento

Un medicamento antiepiléptico

Usado para

Epilepsia

Disponible como

Tablets, oral liquid and injection

Si tienes epilepsia, it means that you have had more than one unexplained fit, or seizure. A seizure is a short episode of symptoms caused by a burst of abnormal electrical activity in your brain. Different parts of the brain control different functions of your body, so the symptoms that occur during a seizure will depend on where the abnormal burst of electrical activity occurs. Symptoms that may occur during a seizure can affect your muscles, sensations, behaviour, emotions, consciousness, or a combination of these. The seizures can be prevented in most people by suitable anti-epileptic medication.

Phenobarbital works by stabilising the electrical activity of your brain, which helps to prevent the seizures from occurring.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine can only be used if extra care is taken. For these reasons, before you start taking phenobarbital it is important that your doctor knows:

  • Si estás embarazada, intentando tener un bebé o amamantando.

  • If you have breathing problems.

  • If you have ever had problems with drug or alcohol dependence.

  • Si tienes algún problema con el funcionamiento de tus riñones o con el funcionamiento de tu hígado.

  • Si tienes un trastorno sanguíneo hereditario raro llamado porfiria.

  • Si está tomando otros medicamentos. Esto incluye cualquier medicamento que se pueda comprar sin receta, así como medicamentos herbales y complementarios.

  • Si alguna vez has tenido una reacción alérgica a un medicamento.

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  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about phenobarbital and will provide you with a full list of the side-effects which you may experience from taking it.

  • Take phenobarbital exactly as your doctor tells you to. It is usual to take one dose a day, at bedtime. Your doctor will tell you how many tablets to take for the dose. This information will also be printed on the label of the pack to remind you about what the doctor said to you. You need to take phenobarbital regularly every day to prevent the fits (seizures) from occurring.

  • Try to take your doses of phenobarbital at the same time each evening. Having a routine like this will help you to remember to take your doses regularly. Swallow the phenobarbital tablets with a drink of water. You can take them either with or without food.

  • Si olvida tomar una dosis, tómela tan pronto como lo recuerde, a menos que esté cerca la hora de su próxima dosis, en cuyo caso omita la dosis olvidada. No tome dos dosis juntas para compensar una dosis olvidada.

  • Try to keep your regular appointments with your doctor. This is so your doctor can check on your progress. You may need to have blood tests from time to time.

  • When you first start a new treatment for epilepsy there may be a change in the number or type of fits (seizures) you experience. Your doctor will advise you about this.

  • Phenobarbital made by different manufacturers can act in a slightly different way in your body. Because of this, it is recommended that you continue to take tablets/medicine from the same manufacturer as you have had before. So, each time you collect a prescription, check to make sure your supply looks the same. If you are unsure, or if have any questions about your prescription, please ask your pharmacist to check it for you.

  • While you are being treated for epilepsy there is a small risk that you may develop mood changes, distressing thoughts and feelings about suicide. If this happens, you must tell your doctor about it straightaway.

  • People with epilepsy must stop driving at first. Your doctor will advise you about when it may be possible for you to resume driving again. This will usually be after a year free of seizures.

  • Do not stop taking this medicine unless your doctor tells you to do so. Stopping it suddenly can cause your seizures to return and your doctor will want you to reduce your dose gradually if this becomes necessary. Also, taking phenobarbital over a time can lead to your body becoming dependent on it and this is another reason why your doctor will want to reduce your dose slowly.

  • You are advised not to drink alcohol while you are taking phenobarbital. Phenobarbital will make you feel sleepy and drinking alcohol will increase this. Some liquid medicines may contain noticeable amounts of alcohol, read the manufacturer's leaflet for more information.

  • If you are due to have an operation or any dental treatment, please tell the person carrying out the treatment that you are taking phenobarbital.

  • If you buy any medicines, check with a pharmacist that they are suitable for you to take alongside phenobarbital.

  • You should avoid becoming pregnant while you are taking phenobarbital because it could cause harm to your unborn baby.

  • If you are a woman using hormonal contraception ('the pill' or the 'mini pill'), discuss this with your doctor, as phenobarbital interferes with these and could mean you are more likely to become pregnant. Other methods of contraception will be more suitable for you.

  • If you want to have a family, make sure you discuss this with your doctor well in advance of becoming pregnant. This is so that you can be given advice from a specialist before you become pregnant. If you become pregnant while you are taking phenobarbital, you should tell your doctor straightaway.

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Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with phenobarbital. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Common phenobarbital side-effects

¿Qué puedo hacer si experimento esto?

Feeling unsteady

Getting up or moving more slowly should help. If this continues, let your doctor know

Sintiéndose somnoliento o cansado

Make sure your reactions are normal before you use tools or machines

Feeling short of breath, behavioural changes, mood changes (such as feeling irritable, confused, excited or depressed), impaired memory

Si alguno de estos se vuelve problemático, hable con su médico

Importante: your doctor will have discussed with you the possibility of some less common but more serious side-effects. Let your doctor know straightaway if you experience any of the following:

  • A high temperature (fever) and swollen glands.

  • Una erupción cutánea severa.

  • Yellowing of your skin or the whites of your eyes (jaundice).

Si experimenta otros síntomas que cree que pueden deberse al medicamento, hable con su médico o farmacéutico para obtener más consejos.

  • Mantenga todos los medicamentos fuera del alcance y la vista de los niños.

  • Almacenar en un lugar fresco y seco, lejos del calor y la luz directos.

  • Liquid medicines should be used within 28 days of opening, unless otherwise stated on the bottle.

Información importante sobre todos los medicamentos

Nunca tome más de la dosis prescrita. Si sospecha que usted u otra persona podría haber tomado una sobredosis de este medicamento, acuda de inmediato al departamento de accidentes y emergencias de su hospital local. Lleve el envase con usted, incluso si está vacío.

Este medicamento es para ti. Nunca lo des a otras personas, incluso si su condición parece ser la misma que la tuya.

No guardes medicamentos caducados o no deseados. Llévalos a tu farmacia local, que se encargará de desecharlos por ti.

Si tienes alguna pregunta sobre este medicamento, consulta a tu farmacéutico.

Informar efectos secundarios de un medicamento o vacuna

Si experimenta efectos secundarios, puede reportarlos en línea a través de sitio web de la Tarjeta Amarilla.

symptom checker

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Verifica posibles interacciones entre medicamentos, suplementos y alimentos antes de tomarlos juntos.

Lecturas adicionales y referencias

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Historial del artículo

La información en esta página está escrita y revisada por pares por clínicos calificados.

  • Next review due: 5 May 2028
  • 5 May 2025 | Última versión

    Última actualización por

    Michael Stewart, MRPharmS

    Revisado por pares por

    Sid Dajani
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