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Phenoxybenzamine - an alpha-blocker

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

Typ av medicin

An alpha-adrenoceptor blocker (also called an alpha-blocker)

Används för

High blood pressure caused by phaeochromocytoma

Tillgänglig som

Kapslar

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 högt blodtryck.

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 phenoxybenzamine it is important that your doctor knows:

  • Om du är gravid eller ammar.

  • If you have problems with the way your kidneys work.

  • If you have heart disease, or if you have recently had a heart attack.

  • If you have ever had a stroke.

  • If you have a rare inherited blood disorder called porphyria.

  • Om du någonsin har haft en allergisk reaktion mot en medicin.

  • Om du tar eller använder några andra läkemedel. Detta inkluderar alla läkemedel du tar som finns att köpa utan recept, samt växtbaserade och komplementära läkemedel.

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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 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.

  • Keep your regular appointments with your doctor. This is so your doctor can check on your progress.

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

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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 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

Vad kan jag göra om jag upplever detta?

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

Om något av dessa blir besvärligt, tala med din läkare

If you experience any other symptoms which you think may be due to the capsules, speak with your doctor or pharmacist for further advice.

  • Förvara alla läkemedel utom räckhåll och synhåll för barn.

  • Förvara på en sval, torr plats, borta från direkt värme och ljus.

Viktig information om alla läkemedel

Ta aldrig mer än den föreskrivna dosen. Om du misstänker att du eller någon annan kan ha tagit en överdos av denna medicin, gå omedelbart till akutmottagningen på ditt lokala sjukhus. Ta med behållaren, även om den är tom.

Denna medicin är för dig. Ge den aldrig till andra människor även om deras tillstånd verkar vara detsamma som ditt.

If you are due to have an operation or dental treatment, please tell the person carrying out the treatment which medicines you are taking.

Behåll inte föråldrade eller oönskade mediciner. Ta dem till ditt lokala apotek som kommer att ta hand om dem åt dig.

Om du har några frågor om denna medicin, fråga din apotekare.

Rapportera biverkningar av ett läkemedel eller vaccin

Om du upplever biverkningar kan du rapportera dem online via Yellow Card website.

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Vanliga frågor

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.

Vidare läsning och referenser

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About the authorView full bio

Author image

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

Author image

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.

Artikelhistorik

Informationen på denna sida är skriven och granskad av kvalificerade kliniker.

  • Nästa granskning: 19 jan 2028
  • 19 jan 2025 | Senaste versionen

    Senast uppdaterad av

    Michael Stewart, MRPharmS

    Granskad av

    Sid Dajani
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