Fenoxibenzamina - un bloqueador alfa
Revisado por pares por Sid DajaniÚltima actualización por Michael Stewart, MRPharmSLast updated 19 Ene 2025
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Adults will normally start with one capsule a day. This dose may then be increased over the next few days.
It is common to feel dizzy or light-headed initially. This should soon settle.
You may be given other medicines to take alongside phenoxybenzamine.
At a glance
Phenoxybenzamine capsules are used to treat high blood pressure caused by a tumour called phaeochromocytoma.
It works by blocking certain sites on your blood vessels, which helps to reduce blood pressure.
You will start with a small dose, which your doctor will gradually increase.
You can take the capsules before or after a meal at the same time each day.
Common side-effects include feeling dizzy or faint when standing up.
If side-effects become troublesome, speak with your doctor.
Always tell your doctor or dentist if you are taking phenoxybenzamine before any treatment.
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About phenoxybenzamine
Tipo de medicamento | An alpha-adrenoceptor blocker (also called an alpha-blocker) |
Usado para | High blood pressure caused by phaeochromocytoma |
Disponible como | Cápsulas |
Phaeochromocytoma is a tumour of your adrenal glands. With phaeochromocytoma, large quantities of chemicals are released from your adrenal glands, which narrow (constrict) your blood vessels. This causes episodes where your blood pressure increases significantly.
The treatment of choice for phaeochromocytoma is removal of the tumour by surgery. Phenoxybenzamine is sometimes prescribed as a short-term option in preparation for the surgery. It works by blocking sites on your blood vessels, known as alpha receptors. This blocking action reduces your presión arterial alta.
Before taking phenoxybenzamine
Volver al contenidoSome 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 phenoxybenzamine it is important that your doctor knows:
Si estás embarazada o amamantando.
Si tienes problemas con el funcionamiento de tus riñones.
If you have heart disease, or if you have recently had a heart attack.
If you have ever had a stroke.
Si tienes un trastorno sanguíneo hereditario raro llamado porfiria.
Si alguna vez has tenido una reacción alérgica a un medicamento.
Si está tomando o usando otros medicamentos. Esto incluye cualquier medicamento que esté tomando y que esté disponible para comprar sin receta, así como medicamentos herbales y complementarios.
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How to take phenoxybenzamine
Volver al contenidoBefore you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about phenoxybenzamine, and will also provide you with a full list of side-effects which you could experience from taking it.
When you start the treatment, your doctor will give you a small dose (one capsule a day) and will then gradually increase your dose over the next few days as necessary. Take phenoxybenzamine capsules exactly as your doctor tells you to. The directions will be printed on the label of the pack of capsules to remind you about what the doctor said to you.
Try to take your doses at the same time of day each day, as this will help you to remember to take them regularly. You can take phenoxybenzamine either before or after a meal. Swallow the capsule with a drink of water.
If you forget to take a dose at your usual time, take it as soon as you remember. If you do not remember until the following day, leave out the forgotten dose from the previous day and take the dose that is due as normal. Do not take two doses at the same time to make up for a missed dose.
Obteniendo el máximo de tu tratamiento
Volver al contenidoMantén tus citas regulares con tu médico. Esto es para que tu médico pueda verificar tu progreso.
If you buy any medicines, check with a pharmacist that they are suitable for you to take alongside phenoxybenzamine.
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Can phenoxybenzamine cause problems?
Volver al contenidoAlong with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains the most common ones associated with phenoxybenzamine. 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 continue or become troublesome.
Phenoxybenzamine side-effects | ¿Qué puedo hacer si experimento esto? |
Feeling dizzy or faint, especially when you get up from a lying or sitting position | Getting up more slowly may help. If you begin to feel dizzy, lie down so that you do not faint, then sit for a few moments before standing. Do not drive and do not use tools or machines while affected |
Feeling tired, blocked nose, eyesight problems, ejaculatory problems, a fast heartbeat, stomach upset, diarrhoea | Si alguno de estos se vuelve problemático, hable con su médico |
If you experience any other symptoms which you think may be due to the capsules, speak with your doctor or pharmacist for further advice.
How to store phenoxybenzamine
Volver al contenidoMantenga 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.
Información importante sobre todos los medicamentos
Volver al contenidoInformación 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.
Si está programado para una operación o tratamiento dental, por favor informe a la persona que realiza el tratamiento qué medicamentos está tomando.
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 Yellow Card website.

¿Inseguro sobre mezclar medicamentos?
Verifica posibles interacciones entre medicamentos, suplementos y alimentos antes de tomarlos juntos.
Preguntas frecuentes
What is the main reason phenoxybenzamine is prescribed?
Phenoxybenzamine is primarily prescribed as a short-term treatment for high blood pressure that is caused by a phaeochromocytoma. This is a tumour that releases large amounts of chemicals, causing blood vessels to narrow and blood pressure to rise significantly. It's used to manage your blood pressure before surgery to remove the tumour.
How does phenoxybenzamine help with high blood pressure?
Phaeochromocytoma causes chemicals to be released which constrict your blood vessels, leading to high blood pressure. Phenoxybenzamine works by blocking specific sites, called alpha receptors, on your blood vessels. This blocking action helps to reduce your high blood pressure.
Can I take phenoxybenzamine if I have other health conditions?
Before starting phenoxybenzamine, it's important to inform your doctor about any existing health conditions. This includes kidney problems, heart disease, if you've had a heart attack or stroke, or if you have a rare inherited blood disorder called porphyria. Your doctor needs this information to ensure the medicine is suitable for you.
Is it important to take phenoxybenzamine at a specific time in relation to meals?
You can take phenoxybenzamine either before or after a meal. The most important thing is to try and take your doses at the same time each day to help you remember to take them regularly.
What should I do if I feel dizzy or faint after taking phenoxybenzamine?
Feeling dizzy or faint, especially when getting up, is a common side-effect. Try getting up more slowly from a lying or sitting position. If you start to feel dizzy, lie down to prevent fainting, and then sit for a few moments before standing. You should avoid driving or operating machinery if you are affected by dizziness.
What should I do if I miss a dose of phenoxybenzamine?
If you forget to take a dose, take it as soon as you remember. However, if you don't remember until the next day, you should skip the missed dose from the previous day and take your next dose as normal. Do not take two doses at the same time to compensate for a forgotten dose.
Can I take other medicines, including over-the-counter ones, with phenoxybenzamine?
It is crucial to inform your doctor about all medicines you are taking, including those available without a prescription, as well as herbal and complementary medicines. If you buy any new medicines while on phenoxybenzamine, always check with a pharmacist if they are suitable to take alongside it.
Lecturas adicionales y referencias
- Manufacturer's PIL, Phenoxybenzamine 10 mg Capsules; Advanz Pharma, The electronic Medicines Compendium. Dated September 2023.
- Medicamentos Completos BNF 89ª Edición; Asociación Médica Británica y Sociedad Real de Farmacia de Gran Bretaña, Londres.
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About the authorView full bio

Michael Stewart, MRPharmS
Medicine Leaflet Review Manager – Contractor, Pharmacist
BPharm (Hons), MRPharmS
Michael is a community pharmacist practicing in the Midlands and South Yorkshire with more than 20 years’ experience advising on medicines and medical conditions. He has a strong background in healthcare training, having produced and delivered training courses for pharmacy teams and staff of residential care settings, including nurses. He has also contributed to pharmacy advisory boards for the management of low acuity conditions in the community.
About the reviewer

Sid Dajani
Sultan Dajani qualified at the London School of Pharmacy in 1994 and became the youngest elected member of the Royal Pharmaceutical Society council since its founding in 1842.
Historial del artículo
La información en esta página está escrita y revisada por pares por clínicos calificados.
Próxima revisión: 19 Ene 2028
19 Ene 2025 | Última versión

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