Cardura XL (Doxazosin)

How does it work?

Cardura XL modified release tablets contain the active ingredient doxazosin, which is a type of medicine called an alpha-blocker. Doxazosin is also available without a brand name, ie as the generic medicine. Doxazosin has two quite different uses. It works by blocking alpha receptors in certain areas of the body.

Alpha receptors are found on the muscle in the walls of blood vessels. When doxazosin blocks these receptors it causes the muscle in the blood vessel to relax and the blood vessel to widen. This lets the blood pass more easily through the blood vessels and hence reduces the pressure in the blood vessels. Doxazosin can therefore be used to treat high blood pressure.

Alpha receptors are also found on the muscle in the prostate gland. This gland is found only in men and lies at the top of the tube connecting the bladder to the outside (urethra). The prostate gland often enlarges with advancing age (benign prostatic hyperplasia), pressing on the urethra and obstructing the flow of urine from the bladder. This can cause various urinary symptoms such as difficulty passing urine. By blocking the alpha receptors, doxazosin causes the muscle in the prostate gland to relax. This allows urine to flow freely past the prostate and relieves the urinary symptoms of this condition.

Cardura XL tablets are modified release tablets. They are designed to release the doxazosin slowly, thus producing a steady blood level of the medicine throughout the day. The tablets must be swallowed whole with a drink and not broken, crushed or chewed, as this would damage the modified release action.

What is it used for?

  • Enlarged prostate gland (benign prostatic hyperplasia).
  • High blood pressure (hypertension).


  • This medication is to be swallowed whole, not chewed.
  • This medicine can occasionally cause your blood pressure to drop when you move from a lying down or sitting position to sitting or standing, especially when you first start taking the medicine. This may make you feel dizzy or unsteady and may rarely cause fainting. To avoid this, take care when moving from lying down to sitting or standing – try getting up slowly. If you do feel dizzy, sit or lie down until the symptoms pass.
  • This medicine may cause fatigue and dizziness. You should take care when performing potentially hazardous activites, such as driving or operating machinery, until you know how this medicine affects you and are sure you can perform such activities safely.
  • Alcohol may enhance the blood pressure lowering effect of this medicine, and this may cause dizziness in some people.
  • If you are scheduled to have eye surgery for cataracts it is important to let your eye specialist know if you are or have been taking this medicine. This is because this type of medicine may make your pupil dilate poorly and the iris (the coloured circular part of the eye) become floppy during the procedure. The specialist needs to know if you have been taking this medicine so they can take appropriate precautions with the medicines and techniques they use during the surgery. You may be asked to stop taking this medicine for a period of time before cataract surgery. Check with your doctor.
  • Cardura XL tablets are designed to release the medicine from the tablet slowly throughout the day. To achieve this the tablet has a specially designed shell that is not absorbed by the body and is excreted in the faeces. You may sometimes notice the tablet shell in your stools. This is normal and nothing to worry about.

Use with caution in

  • Elderly people.
  • Decreased liver function.
  • Heart failure.
  • People with fluid on the lungs (pulmonary oedema) due to heart valve disease or narrowing of the aorta.

Not to be used in

  • People with an allergy to related medicines (quinazolines), eg prazosin, terazosin.
  • People with a history of drops in blood pressure that cause dizziness or fainting when moving from a lying or sitting position to standing (postural hypotension).
  • People with a history of obstruction of the foodpipe (oesophagus), stomach or intestines, or any narrowing of the gastrointestinal tract.
  • As a single treatment in people who cannot fully empty their bladder and so frequently leak urine (overflow incontinence) or who are not producing any urine (anuria).
  • Men with an enlarged prostate gland who also have an ongoing urinary tract infection, blockage of the urinary tract or bladder stones.
  • Men with an enlarged prostate gland who also have low blood pressure.
  • Breastfeeding.
  • This medicine is not recommended for men with an enlarged prostate gland who have ever fainted after passing urine (micturition syncope).
  • This medicine is not recommended for people with severely decreased liver function.
  • The safety and efficacy of this medicine for use in children have not been established. It is not recommended for children.

This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • The safety of this medicine in pregnancy has not been established. It should therefore be used with caution during pregnancy, and only if the benefits to the mother outweigh any potential risks to the developing baby. Seek medical advice from your doctor.
  • This medicine passes into breast milk. It should not be used by women who are breastfeeding. Seek medical advice from your doctor.

Label warnings

  • This medication is to be swallowed whole, not chewed.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

Common (affect between 1 in 10 and 1 in 100 people)

  • Dizziness or spinning sensation.
  • Headache.
  • Sleepiness.
  • Awareness of your heart beat (palpitations) or increased heart rate.
  • A drop in blood pressure that occurs when going from lying down to sitting or standing, which results in dizziness and lightheadedness (postural hypotension).
  • Disturbances of the gut such as nausea, abdominal pain, dry mouth or indigestion.
  • Inflammation of the lining of the nose (rhinitis) causing a blocked or runny nose.
  • Cough or shortness of breath.
  • Itching.
  • Swollen ankles or feet (peripheral oedema).
  • Pain in the muscles (myalgia) or back.
  • Urinary tract infections or urinary incontinence.
  • Chest infections.

Uncommon (affect between 1 in 100 and 1 in 1000 people)

  • Difficulty sleeping (insomnia).
  • Depression or anxiety.
  • Changes in appetite.
  • Numbness.
  • Tremor.
  • Fainting.
  • Sensation of ringing or other noise in the ears (tinnitus).
  • Chest pain (angina).
  • Diarrhoea, constipation, vomiting or wind.
  • Increased need to pass urine.
  • Nose bleeds.
  • Weight gain.
  • Impotence.

Very rare (affect less than 1 in 10,000 people)

  • Blurred vision.
  • Pins and needles sensations.
  • Feeling weak or fatigued.
  • Increased need to pass urine at night.
  • Muscle cramps or weakness.
  • Inflammation of the liver or jaundice.
  • Enlargement of breasts in men.
  • Persistent painful erection of the penis (priapism).
  • Disturbance in the levels of blood cells in the blood.

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to ensure that the combination is safe.

If doxazosin is taken with other medicines that reduce blood pressure, either as a treatment for high blood pressure (antihypertensives), or as a side effect, there may be an enhanced blood pressure lowering effect. This might make some people feel dizzy, particularly when you first start taking the doxazosin. If you do feel dizzy, you should lie down until the symptoms pass. If any dizziness persists you should let your doctor know, as your medicine doses may need adjusting. Other medicines that can reduce blood pressure include the following:

  • ACE inhibitors, eg enalapril, captopril
  • other alpha blockers, eg tamsulosin, terazosin
  • angiotensin II receptor antagonists, eg losartan
  • antipsychotic medicines
  • baclofen
  • benzodiazepines, eg temazepam
  • beta-blockers, eg propranolol
  • calcium channel blockers, eg diltiazem, verapamil, nifedipine
  • diuretics, eg furosemide, bendroflumethiazide
  • levodopa
  • MAOI antidepressants, eg phenelzine
  • nitrates, eg glyceryl trinitrate, isosorbide mononitrate
  • phosphodiesterase type 5 inhibitors for impotence, eg sildenafil, vardenafil, tadalafil.

Other medicines containing the same active ingredient

Cardura Doxadura Doxadura XL

Doxazosin tablets are also available without a brand name, ie as the generic medicine.