Doxazosin

What is doxazosin?

Doxazosin is a type of medication known as an alpha-blocker. It is used to treat high blood pressure, but can also be prescribed for an enlarged prostate.

How does doxazosin work?

Doxazosin works by relaxing blood vessels, which allows the blood to circulate more easily and reduces blood pressure to a healthier level. Doxazosin also relaxes the muscles around the bladder and prostate gland making it easier for men with an enlarged prostate to urinate.

How long will I take doxazosin for?

Doxazosin is a long term treatment to keep your blood pressure at healthy levels. You may have to take blood pressure medication for the rest of your life.

Is long term use of doxazosin safe?

Doxazosin is designed for long term use so it is safe to use in this manner.

What causes high blood pressure?

There are several lifestyle factors which can increase your risk of developing high blood pressure such as being overweight, having a poor diet that is high in salt, not doing enough exercise, drinking too much alcohol, smoking, poor sleep. High blood pressure is also more common in older people, those with a family history of high blood pressure, and those of certain ethnicities. There are several conditions and medications which are known to contribute to the development of high blood pressure. These include: 

• Kidney disease 
• Kidney infections
• Diabetes 
• Obstructive sleep apnoea 
• Glomerulonephritis 
• Narrowed arteries supplying the kidneys 
• Hormone problems 
• Lupus 
• Scleroderma 
• Combined hormonal contraception
• Steroid medications 
• Non-steroidal anti-inflammatory drugs 
• Certain over-the-counter cold and cough remedies 
• Herbal remedies containing liquorice 
• Recreational drugs 
• Selective serotonin noradrenaline reuptake inhibitors (antidepressants)

What are the risks of high blood pressure?

High blood pressure puts a strain on your organs and blood vessels. This can increase your risk of experiencing: 

• Heart disease 
• Heart attacks 
• Strokes
• Heart failure 
• Aortic aneurysms 
• Vascular dementia 
• Kidney disease 
• Peripheral arterial disease
• Antihypertensive medications, such as doxazosin, reduce your blood pressure, helping to reduce your risk of experiencing the conditions above.

Active ingredients

The active ingredient in the medicine is doxazosin.

Inactive ingredients

The other ingredients contained in doxazosin are Lactose monohydrate, magnesium stearate, microcrystalline cellulose, sodium lauryl sulphate, sodium starch glycolate (type A) and colloidal anhydrous silica.

Note the same medication from different manufacturers may contain different inactive ingredients.

Which ingredients can cause an allergic reaction?

Doxazosin is not associated with severe allergic reactions in people using the medication, unless specifically allergic to one of the active or inactive ingredients. If you notice a skin rash, facial swelling, trouble breathing, and dizziness shortly after taking the medication, it is important to seek medical attention immediately.

How to take doxazosin?

Doxazosin should be taken once a day, either in the morning or at night. The tablets should be swallowed whole with a drink of water and can be taken before or after food. Always take doxazosin exactly as your doctor has instructed. 
For immediate-release doxazosin, you will usually begin on a 1 mg dose per day which may be increased after 1–2 weeks. 

Always take the dose specified by your doctor. This can vary depending on the severity of your symptoms.

How long should I use doxazosin for?

Doxazosin is designed for long term use, it is likely that you will have to take it permanently. Your doctor will let you know how long you should take doxazosin.

What should I do if I forget to take doxazosin?

Seek immediate medical assistance if you accidentally take too much doxazosin. Taking too much doxazosin could reduce your blood pressure to dangerously low levels and it also increases your risk of experiencing other side effects.

What should I do if I take too much doxazosin?

Seek medical assistance if you accidentally take too much doxazosin.

Can I dissolve doxazosin in water?

Doxazosin tablets should be swallowed whole with a drink of water. Do not dissolve them or split them unless specifically instructed to do so. Breaking the tablets up can affect how they are absorbed by the body, which can produce unwanted side effects. If you are struggling to swallow your tablet, speak to your doctor for advice, as they may be able to suggest an alternative soluble medication instead.

Common side effects (happening in up to 1 in 10 people) may include: 

• Dizziness or vertigo 
• Headaches 
• Low blood pressure 
• Swelling in the feet, ankles or fingers 
• Coughing 
• Chest cold 
• Respiratory tract infection 
• Sneezing, runny nose or stuffiness in the nose
• Abdominal pain 
• Nausea 
• Vomiting 
• Feeling tired 
• Weakness 
• Indigestion 
• Itching
• Back pain 
• Muscle pain 
• Flu-like symptoms 

Uncommon side effects (happening in up to 1 in 100 people) may include: 

• Constipation or diarrhoea
• Gastroenteritis 
• Difficulty passing urine 
• Gout 
• Swelling in the face
• Sleeplessness 
• Agitation or nervousness 
• Anxiety or depression 
• Reduced feeling in the hands and feet 
• Weight gain
• Altered appetite 
• Skin rash
• Ringing in the ears 
• Erectile dysfunction 
• Stroke

Rare side effects (happening in up to 1 in 1,000 people) may include: 

• Frequent urination 
• Muscle cramps or weakness 

Very rare side effects (happening in up to 1 in 10,000 people) may include: 

• Low blood pressure leading to fainting 
• Hepatitis (inflammation of the liver)
• Hives 
• Hair loss 
• Worsening of wheeze
• Blurred vision 
• Tingling in the hands or feet
• Hot flushes 
• Discomfort or breast enlargement in men
• Tiredness

If you experience any of the following serious side effects after taking doxazosin tell your doctor right away: 

• Shortness of breath
• Altered heartbeat or palpitations
• Angina (chest pain)
• Jaundice (yellowing of the skin or whites of the eyes)
• Lowered number of white blood cells which can cause easy bruising or bleeding, or picking up infections easily
• Persistent and painful erections

Call an ambulance if you experience any of the following:

• Symptoms of a heart attack – e.g. chest pain, shoulder pain, feeling sweaty or clammy and shortness of breath
• Symptoms of a stroke – e.g. sudden weakness, facial drooping, difficulty speaking or confusion
• Symptoms of allergic reaction – e.g. sudden swelling of the face, mouth or throat, rash, or difficulty breathing

How to cope with doxazosin side effects?

If doxazosin makes you feel dizzy, weak or sleepy, sit or lie down until you feel better and avoid driving or using tools. Drinking alcohol is likely to make side effects worse. Take your medication at night if it is making you feel sleepy. Drink plenty of fluids, get enough rest and take a painkiller like Paracetamol if you are getting headaches. Elevate your legs while sitting down if your feet and ankles are swollen and avoid eating meals that are too rich or spicy if you feel sick.

Contraindications

Do not take doxazosin if you: 

• Are allergic to any of the ingredients contained in doxazosin, or any other types of quinazolines (e.g. prazosin, terazosin)
• Are breastfeeding 
• Have an enlarged prostate and low blood pressure 
• Have a history of orthostatic hypotension 
• Have an enlarged prostate alongside a congestion or blockage in the urinary tract, a long term urinary tract infection or bladder stones 
• Have overflow incontinence 
• Have anuria 
• Have a history of micturition syncope (fainting when passing urine)

Tell your doctor if any of the following apply to you before taking doxazosin: 

• Liver disease 
• Heart disease or heart valve conditions
• Pulmonary oedema
• You are pregnant or trying to get pregnant 
• You are taking other medications 
• You are scheduled to have an eye operation for cataracts
• You are over the age of 65

Drug interactions

The following medications may interfere with doxazosin: 

• PDE-5 inhibitors e.g. sildenafil (Viagra)
• Any other medications designed to lower your blood pressure
• Antibiotics such as Clarithromycin and Telithromycin
• Antifungals such as Itraconazole and Ketoconazole 
• HIV medications 
• Nefazodone

Doxazosin and pregnancy

If you are pregnant or planning to become pregnant, talk to your doctor before taking doxazosin as other medications may be more suitable.

Doxazosin and breastfeeding

You should talk to your doctor if you are breastfeeding so that they can establish the safety of taking doxazosin. 

Doxazosin and alcohol

It's best to avoid drinking alcohol when you start taking doxazosin. Alcohol can increase the effects of doxazosin, reducing your blood pressure significantly and causing lightheadedness and dizziness.

Can I take painkillers with doxazosin?

You can take paracetamol alongside doxazosin but it's recommended that you avoid anti-inflammatory medications like Ibuprofen as these can increase your blood pressure.

Will doxazosin affect my contraception?

Doxazosin will not have an effect on your contraception. It is not usually recommended for women with high blood pressure to take the combined oral contraceptive pill, and in this case your doctor may recommend an alternative method of contraception such as the progestogen-only pill, subdermal implant, injection or an intrauterine contraceptive device.

Will Doxazosin affect my fertility?

Doxazosin will not have an affect on your fertility but if you are trying to get pregnant speak to a doctor to ensure the medication is suitable for you. 

Will doxazosin affect my sex life?

Some rare side effects of doxazosin in men include erectile dysfunction, painful erections or no semen during ejaculation. Talk to your doctor if this is an issue for you. Doxasosin is not known to cause any adverse effects on sexual function in women.

Can I drive while taking doxazosin?

Doxazosin may cause dizziness when you first start to take it. Do not drive, ride a bike or operate machinery until you know how doxazosin affects you.

Is there any food or drink I need to avoid while taking doxazosin?

Eating a healthy diet is recommended while taking doxazosin in order to maintain healthy blood pressure levels.

Alternatives to doxazosin

There are several other types of medications that treat high blood pressure such as ACE inhibitors, angiotensin receptor blockers (ARBs), calcium channel blockers, beta-blockers and diuretics. If you’re under 55, you'll usually be offered an ACE inhibitor or ARB in the first instance if you’re under 55. But, if you are of African or Caribbean origin or if you are over the age of 55, you will likely be prescribed a calcium channel blocker as the first line treatment. This is because, evidence shows that calcium channel blockers are more effective in different ethnicities and in those over 55.

Can lifestyle changes help high blood pressure?

Everyone with high blood pressure is recommended to make lifestyle changes including: 

• Reducing your consumption of salt to less than 6 grams a day 
• Eat a healthy diet that is low in saturated fat and includes plenty of fruit and vegetables 
• Get regular exercise 
• Maintain a healthy weight 
• Cut down on caffeine 
• Quit smoking 
• Get plenty of sleep

Can lifestyle changes help an enlarged prostate?

There are lifestyle changes you can make to help reduce an enlarged prostate. These include: 

• Cut down on fizzy drinks, artificial sweeteners, caffeine and alcohol 
• Drink less in the evenings and avoid drinking fluids up to two hours before bed 
• Empty your bladder regularly 
• Consume more fruit and fibre

What is the difference between immediate-release and modified-release doxazosin?

Immediate-release medications work more quickly and tend to have a shorter duration of action. Modified-release medications release the medication more slowly and tend to have a longer duration of action. Both immediate-release and modified-release are given once per day so it’s thought that modified-release does not offer any significant advantage. It’s possible that a modified-release formulation may have a more favourable side effect profile than an immediate-release formulation. Speak to your doctor if you feel that a different version may be more suitable for you.