Doxazosin belongs to a group of medicines called alpha-blockers.
This medicine is only available on prescription and comes as tablets.
- 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.
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
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.
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)
- 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).
These are not all the side effects of doxazosin.
For a full list, see the leaflet inside your medicines packet.
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.
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.
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.