Fenobarbital para la epilepsia
Revisado por Sid DajaniÚltima actualización por Michael Stewart, MRPharmSÚltima actualización 5 de mayo de 2025
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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.
De un vistazo
Phenobarbital is an anti-epileptic medicine used to prevent seizures.
Funciona estabilizando la actividad eléctrica en tu cerebro.
Take phenobarbital exactly as your doctor tells you, usually once a day at bedtime.
Do not stop taking this medicine suddenly, as this could cause seizures to return.
Avoid alcohol and discuss contraception with your doctor, as phenobarbital can interfere with it.
Tell your doctor if you experience a high temperature, severe skin rash, or yellow skin/eyes.
About phenobarbital
Tipo de medicamento | Un medicamento antiepiléptico |
Usado para | Epilepsia |
Disponible como | Tabletas, líquido oral e inyección |
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.
Before taking phenobarbital
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.
Si tienes problemas para respirar.
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.
How to take phenobarbital
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.
Obteniendo el máximo de tu tratamiento
Intenta mantener tus citas regulares con tu médico. Esto es para que tu médico pueda verificar tu progreso. Es posible que necesites hacerte análisis de sangre de vez en cuando.
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.
Mientras estás siendo tratado por epilepsia, existe un pequeño riesgo de que puedas desarrollar cambios de humor, pensamientos angustiantes y sentimientos sobre el suicidio. Si esto ocurre, debes informar a tu médico de inmediato.
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.
Can phenobarbital cause problems?
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 cualquier otro síntoma que crea que puede deberse al medicamento, hable con su médico o farmacéutico para obtener más consejos.
How to store phenobarbital
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
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, donde se encargarán 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 Yellow Card.

¿No estás seguro sobre mezclar medicamentos?
Verifica posibles interacciones entre medicamentos, suplementos y alimentos antes de tomarlos juntos.
Preguntas frecuentes
What is epilepsy and why do I need phenobarbital?
Epilepsy means you've had more than one unexplained fit or seizure. Seizures are caused by abnormal electrical activity in your brain. Phenobarbital helps to prevent these seizures by stabilising your brain's electrical activity.
Can I drive while taking phenobarbital?
Initially, you must stop driving. Your doctor will advise you on when it's safe to resume, usually after a year without any seizures.
Are there any specific situations where I should inform a healthcare professional that I'm taking phenobarbital?
Yes, you should always tell the person carrying out treatment that you are taking phenobarbital if you are due to have an operation or any dental treatment. Also, if you buy any other medicines, check with a pharmacist to ensure they are suitable to take alongside phenobarbital.
Should I be concerned about my mood or thoughts while on phenobarbital?
While being treated for epilepsy, there's a small risk of developing mood changes, distressing thoughts, or feelings about suicide. If this happens, you must tell your doctor straightaway.
What should I do if I get my phenobarbital from a different manufacturer?
Phenobarbital from different manufacturers can act slightly differently in your body. It's recommended to continue taking medicine from the same manufacturer. Always check your supply each time you collect a prescription, and if you're unsure, ask your pharmacist.
What should I do if I notice yellowing of my skin or eyes, or a severe skin rash?
These are less common but more serious side-effects. You should let your doctor know straightaway if you experience yellowing of your skin or the whites of your eyes (jaundice) or a severe skin rash.
Lecturas adicionales y referencias
- Manufacturer's PIL, Phenobarbital Thornton & Ross 15mg/5ml Elixir; Thornton & Ross Ltd, The electronic Medicines Compendium. Dated September 2020.
- Medicamentos Completo BNF 89ª Edición; Asociación Médica Británica y Sociedad Real de Farmacia de Gran Bretaña, Londres.
Acerca del revisor

Sid Dajani
Sultan Dajani se graduó en la Escuela de Farmacia de Londres en 1994 y se convirtió en el miembro más joven elegido para el consejo de la Sociedad Real de Farmacia desde su fundación en 1842.

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