Doxazosin - an alpha-blocker

Take doxazosin once each day. Take your first dose at bedtime.

As your body is getting used to doxazosin you may feel dizzy or light-headed when standing up or sitting up quickly - getting up more slowly will help.

Do not drive or use tools or machines if you feel tired or dizzy.

Type of medicine An alpha-blocker
Used for Enlargement of the prostate gland in men; and hypertension (high blood pressure)
Also called Cardozin®; Cardura®; Colixil®; Doxadura®; Doxzogen®; Larbex®; Raporsin®; Slocinx®
Available as Tablets and modified-release tablets

Doxazosin belongs to a group of medicines known as alpha-blockers. It works by blocking the action of certain nerve impulses. This blocking action is useful in two different medical conditions. It is used to help control the symptoms of prostate gland enlargement, and it also reduces blood pressure in people with hypertension.

The prostate gland commonly becomes larger in older men. Prostate gland enlargement is also called benign prostatic hyperplasia (BPH). It can cause problems with passing urine, such as having to wait before your urine starts to flow, taking longer at the toilet, dribbling, and a feeling that your bladder is not quite empty. Doxazosin works by relaxing the muscles around your bladder and prostate so that you can pass urine more easily.

In people with high blood pressure, doxazosin works by relaxing blood vessel walls. This allows blood and oxygen to circulate more freely around your body and lowers your blood pressure.

Doxazosin is available as a standard tablet and also as a modified-release tablet. Modified-release tablets have the letters 'XL' after their brand name - these release doxazosin more slowly and evenly throughout the course of the day.

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

  • If you are pregnant, trying for a baby or breast-feeding.
  • If you ever feel dizzy or faint when you stand up, or if you have ever fainted after passing urine.
  • If you are due to have cataract eye surgery.
  • If you have any problems with the way your liver works.
  • If you have been told you have heart failure.
  • If you have ever had an allergic reaction to a medicine.
  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • Before you start this treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about doxazosin and will provide you with a full list of the side-effects which you may experience from taking it.
  • There are several strengths of doxazosin tablet. When you first start the treatment, your doctor may give you a low dose which will then later be increased. This allows your doctor to make sure that you have the dose that helps your condition and avoids any unwanted symptoms.
  • Your first dose of doxazosin may make you feel faint, so it is important that you take this dose at bedtime. If you feel dizzy or weary, or if you start sweating, remain lying down until these symptoms have gone.
  • Take doxazosin once each day. After your first dose (which should be taken at bedtime), try to take your doses at the same time of day each day - you can generally choose a time of day that suits you. This will help you to avoid missing doses.
  • Swallow the tablet with a drink of water. You can take doxazosin before or after meals.
  • If you have been given modified-release tablets (these have 'XL' after the brand name), these should be swallowed whole. Do not chew or break the tablets to help you swallow.
  • If you forget to take a dose, take it as soon as you remember. If you do not remember until the following day, skip the missed dose - do not take two doses together to make up for a forgotten dose.
  • Doxazosin can make you feel dizzy, particularly when you first start taking it. Make sure your reactions are normal before you drive or use tools or machines which would be dangerous if you are not fully alert.
  • You are advised not to drink alcohol while you are on doxazosin. Alcohol will increase the side-effects of doxazosin, such as feeling faint and dizzy.
  • Try to keep your regular appointments with your doctor. This is so your doctor can check on your progress.
  • If you are having an operation or medical treatment, tell the person carrying out the treatment that you are taking doxazosin. This is because your blood pressure may drop suddenly if you have an anaesthetic. If you are having cataract surgery, it is particularly important that you tell your eye surgeon that you are on doxazosin. This is because an eye problem known as 'floppy iris syndrome' has developed in some people taking medicines similar to doxazosin, so your doctor may advise you to stop taking it for a short while.
  • If you buy any medicines check with a pharmacist that they are suitable to take with your other medicines. Some anti-inflammatory painkillers (called NSAIDs) can reduce the blood pressure lowering effect of doxazosin.

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 doxazosin. 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 doxazosin side-effects (these affect less than 1 in 10 people)
What can I do if I experience this?
Feeling tired, dizzy or faint If any of these happen, do not drive or use tools or machines until you feel better. Do not drink alcohol
Headache, other aches and pains Ask your pharmacist to recommend a suitable painkiller
Swollen feet or ankles When you sit down, rest your legs on a low stool
Dry mouth Try chewing sugar-free sweets or sugar-free gum
Feeling sick, indigestion Stick to simple foods - avoid rich or spicy meals
Chest and urinary infections, palpitations, feeling itchy If any of these become troublesome, speak with your doctor

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

  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine, ask your pharmacist.

Further reading & references

  • British National Formulary; 67th Edition (March 2014) British Medical Association and Royal Pharmaceutical Society of Great Britain, London

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Dr Hannah Gronow
Document ID:
3375 (v29)
Last Checked:
23/06/2014
Next Review:
22/06/2017
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