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Doxazosin

1. About doxazosin

Doxazosin belongs to a group of medicines called alpha-blockers.

It's used to treat high blood pressure and symptoms of an enlarged prostate (benign prostatic enlargement).

This medicine is only available on prescription and comes as tablets.

2. Key facts

  • Doxazosin lowers blood pressure by relaxing your blood vessels so blood can pass through more easily.
  • Doxazosin helps reduce the symptoms of an enlarged prostate gland by relaxing the muscle around the bladder and prostate gland so you can pee more easily.
  • You usually take it once a day. You can take it in the morning or evening, but it's best to take it at the same time every day.
  • The main side effects of doxazosin are feeling dizzy or feeling like you or everything around you is spinning (vertigo), headaches, swollen feet, ankles or fingers, needing to pee suddenly or more often, or pain in your lower stomach (abdomen).
  • Doxazosin also goes by the brand name Cardura, Raporsin or Slocin.

3. Who can and can't take doxazosin

Doxazosin can be taken by adults only.

Do not give this medicine to children under the age of 18 years, unless a specialist children's doctor prescribes it.

Doxazosin is not suitable for some people.

To make sure this medicine is safe for you, tell your doctor if you:

  • have ever had an allergic reaction to doxazosin or other similar medicines, such as alfuzosin, prozosin, tamsulosin or terazosin
  • are pregnant or breastfeeding
  • have orthostatic hypotension - a type of low blood pressure that can make you feel dizzy or light-headed when you stand up
  • have an enlarged prostate gland and low blood pressure
  • have an enlarged prostate gland and bladder stones or a blockage or longstanding infection in your urinary tract
  • have an enlarged prostate gland and you faint when peeing or shortly after peeing
  • do not feel the urge to pee or your body is not producing any pee
  • are due to have cataract surgery

4. How and when to take it

Doxazosin comes as 2 different types of tablet: immediate release and prolonged release (also called XL).

Prolonged-release tablets release the doxazosin more slowly than the immediate-release tablets. Both types of tablets are taken once a day.

Doxazosin immediate-release tablets come in 4 strengths: 1mg, 2mg, 4mg and 8mg.

Doxazosin prolonged-release tablets come in 2 strengths: 4mg and 8mg.

How much will I take?

The dose of doxazosin can vary. How much you take depends on why you need doxazosin and the type of tablet you're taking.

The usual dose for high blood pressure:

  • immediate release - 2mg to 16mg, taken once a day
  • prolonged release - 4mg or 8mg, taken once a day

The usual dose for enlarged prostate gland:

  • immediate release - 2mg to 8mg, taken once a day
  • prolonged release - 4mg or 8mg, taken once a day

You may have to take more than 1 tablet to make up your dose (for example, 2 of the 8mg tablets to make up a 16mg dose).

Your doctor will tell you how many tablets to take each day.

How to take it

Take your doxazosin tablets with a glass of water. Swallow them whole. Do not chew them.

You can take them with or without food.

You can take doxazosin in the morning or evening, but it's best to take it at the same time each day.

Some immediate-release tablets have a score line to help you break the tablet and make it easier to swallow. Check your medicine's information leaflet to see if you can do this.

Will my dose go up or down?

Your doctor will start you on a lower dose.

If you're taking the immediate-release tablets, your doctor will usually start you on 1mg. They'll then gradually increase your dose until your condition is under control.

With the prolonged-release tablets, your doctor will usually start you on 4mg and this may be increased to 8mg.

What if I forget to take it?

If you miss a dose of doxazosin, skip the missed dose. Take the next dose at the usual time. Do not take a double dose to make up for a forgotten dose.

If you forget doses often, it may help to set an alarm to remind you.

You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

Taking too much doxazosin can reduce your blood pressure and increase your heart rate. You may feel drowsy, faint and lightheaded.

Urgent advice: Call your doctor or go to A&E if you take too much doxazosin

If you feel unwell, do not drive yourself. Get someone else to drive you or call an ambulance.

Take the doxazosin packet, or the leaflet inside it, with you, plus any remaining medicine.

Find your nearest A&E

5. Side effects

Like all medicines, doxazosin can cause side effects, but many people have no side effects or only minor ones.

Side effects often improve as your body gets used to the medicine.

Common side effects

These common side effects happen in more than 1 in 100 people. They're usually mild and short-lived.

Talk to your doctor or pharmacist if these side effects bother you or last more than a few days:

  • feeling weak, sleepy or dizzy, or feeling like you or everything around you is spinning (vertigo)
  • headaches
  • swollen feet, ankles or fingers
  • urinary tract infection (UTI), urinary incontinence, cystitis - this can include needing to pee suddenly or more often than usual, pain or a burning sensation when peeing, and smelly or cloudy pee
  • stomach pain, including pain in the lower stomach (abdomen) due to an enlarged prostate
  • feeling or being sick (nausea or vomiting)

Serious side effects

Tell your doctor straight away if you get:

  • chest pain, an irregular heartbeat or you can feel your heartbeat (palpitations) - these can be signs of heart problems
  • weak arms or legs or problems speaking - these can be signs of a stroke
  • shortness of breath or difficulty breathing - these can be signs of lung problems
  • yellow skin or the whites of your eyes turning yellow - these can be signs of liver problems
  • bruising or easy bleeding - these can be signs of a blood problem
  • a painful erection that lasts 4 or more hours

Serious allergic reaction

In rare cases, doxazosin may cause a serious allergic reaction (anaphylaxis).

Urgent advice: Contact a doctor straight away if you:

  • get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • are wheezing
  • get tightness in the chest or throat
  • have trouble breathing or talking
  • get swelling in your mouth, face, lips, tongue or throat

These are warning signs of a serious allergic reaction.

A serious allergic reaction is an emergency.

These are not all the side effects of doxazosin.

For a full list, see the leaflet inside your medicines packet.

Information:

You can report any suspected side effect to the UK safety scheme.

6. How to cope with side effects

What to do about:

  • feeling weak, sleepy or dizzy, feeling like the room/everything around you is spinning (vertigo) - if doxazosin makes you feel like this, stop what you're doing and sit or lie down until you feel better. Do not drive or use tools or machinery. Do not drink alcohol, as it'll make you feel worse. If you feel sleepy, it may help to take your medicine at night time. If you're still feeling dizzy after a week, or all of the time, speak to your doctor.
  • headaches - make sure you rest and drink plenty of fluids. Do not drink too much alcohol. Ask your pharmacist to recommend a painkiller. Talk to your doctor if the headaches are severe or last longer than a few days.
  • swollen feet or ankles - get plenty of rest and raise your legs when you're sitting down. Try not to stand for a long time.
  • UTI, urinary incontinence, cystitis - rest and drink plenty of fluids. This helps your body to flush out bacteria.
  • stomach pain - try to rest and relax. It can help to eat and drink slowly, and have smaller and more frequent meals. Take a painkiller like paracetamol. Place a hot water bottle on your tummy or back, or between your thighs. If the pain is in your lower stomach because of an enlarged prostate, it's best not to have sex until you're feeling better. It may feel uncomfortable or make the pain worse. If you're in a lot of pain, speak to your pharmacist or doctor.
  • feeling or being sick - stick to simple meals and avoid rich or spicy food. It might help to take your doxazosin after you have eaten. Drink plenty of fluids. If you're being sick, take small, frequent sips to avoid dehydration.

7. Pregnancy and breastfeeding

Doxazosin is not usually recommended in pregnancy. It's not clear whether doxazosin can harm your unborn baby.

For safety, your doctor will probably suggest a different medicine that can be used for high blood pressure in pregnancy.

If you're trying to get pregnant or already are pregnant, talk to your doctor about the benefits and possible harms of taking doxazosin.

Doxazosin and breastfeeding

If you take doxazosin while breastfeeding, there's a risk of very small amounts of doxazosin getting into your breast milk.

This would not usually cause problems for your baby, but your doctor may prescribe a different medicine for your blood pressure.

If you're trying to get pregnant, are already pregnant or breastfeeding, talk to your doctor about the benefits and possible harms of taking doxazosin.

Your doctor will be able to recommend the best treatment for you and your baby.

Non-urgent advice: Tell your doctor if you're:

  • trying to get pregnant
  • pregnant
  • breastfeeding

8. Cautions with other medicines

There are some medicines that interfere with the way doxazosin works.

Tell your doctor or pharmacist if you're taking:

  • medicines for erectile dysfunction, such as sildenafil, tadalfil or vardenafil
  • other medicines for high blood pressure - when taking doxazosin they can sometimes lower your blood pressure too much
  • other medicines that can lower your blood pressure - this includes some antidepressants, muscle relaxants like baclofen, medicines for chest pain like nitrates, and medicines for Parkinson's disease like co-careldopa and levodopa
  • ketoconazole, a medicine usually used for fungal infections

Taking doxazosin with painkillers

Non-steroidal anti-inflammatory medicines (NSAIDs), such as ibuprofen, may increase your blood pressure, so it's best to keep them to a minimum.

You can take paracetamol or codeine safely with doxazosin.

Mixing doxazosin with herbal remedies and supplements

There are no known problems with taking herbal remedies and supplements alongside doxazosin.

Important

For safety, tell your doctor or pharmacist if you're taking any other medicines, including herbal medicines, vitamins or supplements.

9. Common questions

How does it work?

Doxazosin belongs to a group of medicines called alpha-adrenoceptor blocking drugs or "alpha-blockers".

They reduce blood pressure by relaxing your blood vessels so blood can pass through them more easily.

Doxazosin also helps reduce the symptoms of an enlarged prostate gland by relaxing the muscle around the bladder and prostate gland so you can pee more easily.

How long will I take it for?

Usually, treatment with doxazosin is long term, even for the rest of your life.

Is it safe to take for a long time?

Doxazosin is generally safe to take for a long time.

In fact, it works best when you take it for a long time.

What will happen if I stop taking it?

Talk to your doctor if you want to stop taking doxazosin.

Stopping doxazosin suddenly can make your condition worse.

If you're bothered by side effects, your doctor may be able to prescribe a different medicine for your blood pressure or enlarged prostate.

If you stop taking doxazosin, it'll take 4 to 5 days for it to be completely out of your body.

How does it compare with other heart medicines?

There are lots of other medicines to lower your blood pressure.

They work in a different way from alpha blockers, and include:

Alpha blockers are not usually the first-choice treatment for high blood pressure.

The medicine your doctor prescribes depends on your age and ethnicity.

If you're under 55, you'll usually be offered an ACE inhibitor or an angiotensin receptor blocker first.

If you're 55 or older, or you're any age and of African Caribbean or black African origin, you'll usually be offered a calcium channel blocker first.

If you get side effects, you may have to try other blood pressure-lowering medicines.

Many people need to take a combination of different blood pressure-lowering tablets.

Will I need to stop taking doxazosin before surgery?

Tell your doctor if you're taking doxazosin and going to have cataract surgery.

Your doctor may advise you to stop taking doxazosin 2 weeks before surgery.

This is because doxazosin may cause complications during the cataract operation.

If you're having other types of surgery, talk to your nurse or doctor at your pre-assessment appointment.

They'll tell you if you need to stop taking doxazosin.

Can I drink alcohol with it?

Drinking alcohol can increase the blood pressure-lowering effect of doxazosin, which can make you feel dizzy or lightheaded.

During the first few days of taking doxazosin or after an increase in your dose, it's best to stop drinking alcohol until you see how the medicine affects you.

If you find taking doxazosin makes you feel dizzy, it's best to stop drinking alcohol.

Is there any food or drink I need to avoid?

You can eat and drink normally while taking doxazosin.

Eating a healthy, balanced diet can help if you have high blood pressure or a heart problem.

Will it affect my contraception?

Doxazosin will not stop your contraception working.

But some types of hormonal methods of contraception, such as the combined pill and contraceptive patch, are not usually recommended for women with high blood pressure.

Talk to your doctor if you're taking a combined hormonal contraceptive.

Will it affect my fertility?

There's no firm evidence to suggest that taking doxazosin will reduce fertility in either men or women.

But speak to a pharmacist or your doctor before taking it if you're trying to get pregnant.

Will it affect my sex life?

Some men taking doxazosin say they cannot get an erection. This is an uncommon side effect and will only affect up to 1 in 100 people.

Some men have also experienced long-lasting and painful erections.

This is very rare, but if it does happen, contact a doctor straight away as it could cause tissue damage.

Some men have also reported little or no semen ejaculated during sex or cloudy pee after sex.

But this is not a common side effect and there's not enough evidence to say for sure that doxazosin is causing it.

Tell your doctor or pharmacist if you're taking medicines for erectile dysfunction, such as sildenafil, tadalfil or vardenafil.

If you take doxazosin with these medicines, you may feel dizzy or lightheaded.

You may be asked to leave a 6-hour gap between taking the doxazosin and any medicines for erectile dysfunction.

If you're having problems with your sex life, talk to your doctor.

Do I need to avoid playing sports?

You do not need to stop playing sports if you take doxazosin. But do not push yourself too much.

When you first start doxazosin, it may make you feel dizzy or weak. If this happens, it's best to sit or lie down until you feel better.

Regular exercise is good for you because it lowers blood pressure by keeping your heart and blood vessels in good condition.

Can I drive or ride a bike?

Doxazosin can make some people feel dizzy, especially when they first start taking it or after taking a bigger dose.

If this happens to you, do not drive a car, ride a bike, or use tools or machinery until you feel OK again.

Can lifestyle changes help high blood pressure?

If you're taking doxazosin to treat high blood pressure, the following lifestyle changes can help:

Can lifestyle changes help symptoms of an enlarged prostate gland?

If you're taking doxazosin to treat symptoms of an enlarged prostate gland, you might be able to relieve the symptoms by making some simple changes to your lifestyle:

  • drink fewer fizzy drinks and less alcohol, and cut back on caffeine (like tea, coffee or coke) and artificial sweeteners - these can irritate the bladder and make peeing more uncomfortable
  • drink less in the evening - try to reduce the amount you drink in the evening and avoid drinking anything for 2 hours before you go to bed. This might help you avoid getting up in the night. Make sure you're still drinking enough fluid earlier in the day.
  • empty your bladder - remember to go to the toilet before long journeys if you know you will not be able to reach a toilet easily
  • try "double voiding" - this means waiting a few moments after you have finished peeing before trying to go again. It can help you empty your bladder properly. But take care not to strain or push.
  • check your medicines - check with your doctor whether any medicines you take, such as antidepressants or decongestants, may be making your symptoms worse.
  • eat more fruit and fibre - eating more fruit and fibre will help you avoid constipation, which can put pressure on the bladder and make symptoms of an enlarged prostate worse