Doxazosin

What is doxazosin?

Doxazosin is a prescription medicine used to treat high blood pressure (hypertension) and symptoms of benign prostatic hyperplasia (BPH) a condition involving an enlarged prostate in men. It is available under the brand names Cardura and Cardura XL as well as generic formulations[1]. 

Doxazosin belongs to a group of drugs called alpha-1 blockers, which work by relaxing certain muscles in the body[1]. 

How does doxazosin work?

Doxazosin works by selectively blocking alpha-1 adrenergic receptors relaxing smooth muscle in specific areas of the body. For hypertension, it relaxes blood vessel walls so blood can flow more easily, helping to lower blood pressure. For BPH, it relaxes muscles in the prostate and bladder neck, relieving urinary obstruction and improving urine flow[1]. 

Who can take doxazosin?

Doxazosin is prescribed for adults, including older adults, but is not licensed for use in children in the UK. It may be unsuitable for individuals with certain conditions, including liver problems, low blood pressure, digestive tract blockages, or those planning cataract surgery (due to the risk of intraoperative floppy iris syndrome (IFIS))[1]. 

Consult your doctor or pharmacist before starting doxazosin if you have these conditions or a history of heart disease, kidney impairment, or urinary incontinence[1]. 

Please tell your doctor or pharmacist about any conditions you may have before you start treatment, and always follow the instructions in the Patient Information Leaflet[2]. 

What is the typical dosage of doxazosin?

The dosage of doxazosin varies depending on the condition being treated. For hypertension or BPH the usual starting dose is 1mg once daily, typically taken at bedtime to reduce the risk of dizziness or fainting due to postural hypotension. The dose may be gradually increased by your doctor to 2–8 mg once daily for hypertension or up to 8 mg for BPH, based on your response[1]. 

Always follow your doctor’s or pharmacist’s instructions and do not adjust your dose without medical advice. 

How do you take doxazosin?

Doxazosin is typically taken once daily, with or without food, preferably at the same time each day to maintain consistent blood levels. Standard tablets should be swallowed whole with water and not crushed or chewed. Extended-release tablets (for example Cardura XL) must not be crushed or chewed, as this can affect how the medicine is absorbed. If you have difficulty swallowing, speak to your pharmacist for advice[1]. 

Can you stop taking doxazosin suddenly?

Do not stop taking doxazosin suddenly unless advised by your doctor. Stopping abruptly could cause your blood pressure to rise again (rebound hypertension) or worsening of BPH symptoms. If discontinuation is needed, your doctor may gradually reduce your dose to minimise these risks[1]. 

What should you do if you take too much doxazosin?

Taking too much doxazosin may lead to symptoms such as severe dizziness or fainting, rapid heartbeat, or low blood pressure. If you suspect an overdose, seek emergency medical attention immediately or contact NHS 111 for guidance[1]. 

What should you do if you forget a dose of doxazosin?

If you forget a dose of doxazosin, you can usually simply take the missed dose. If, however, it’s nearly time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose at any time[1]. 

Which medicines should you avoid while taking doxazosin?

Doxazosin can interact with many other medicines and potentially leading to adverse effects. That’s why it’s important to tell your doctor about all medicines and supplements you’re taking[1]. 

You should avoid doxazosin when taking[1]: 

• Other blood pressure medications which can cause low blood pressure 

• Phosphodiesterase inhibitors (like sildenafil, or Viagra) which may cause a sudden drop in blood pressure 

• NSAIDs (e.g., ibuprofen) that may reduce how well doxazosin works 

• CYP3A4 inhibitors (e.g., ketoconazole) which can increase doxazosin levels in the body 

Always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[2]. 

What are the side effects of doxazosin?

The most common side effects experienced when taking doxazosin are dizziness, light-headedness (especially when standing up), tiredness, headache, and swelling in your legs or feet[1].  

Rarer but more serious side effects – for which you should seek medical help – are[1]: 

• Fainting 

• Chest pain 

• Irregular heartbeat 

• Shortness of breath 

• Signs of an allergic reaction (such as a rash, itching, or swelling of the face or throat) 

If you feel faint or dizzy, especially after the first dose of doxazosin, lie down and get medical advice. 

If any side effects are worrying, severe, or persistent, contact your doctor.

If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice.

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional[2]. 

Frequently asked questions about doxazosin

Can women take doxazosin? 

Yes, women can take doxazosin for high blood pressure. It is not used for BPH in women as this condition only affects men[1]. 

Can I drink alcohol while taking doxazosin? 

Alcohol can increase the risk of dizziness or fainting particularly when starting doxazosin or after a dose increase. As such, you should exercise caution if drinking alcohol alongside doxazosin, especially when you are just starting treatment consult your doctor or pharmacist for advice[1]. 

How long does doxazosin take to work? 

For hypertension, doxazosin may begin lowering blood pressure within hours, with optimal effects typically seen within 1 to 2 weeks. For BPH, symptom improvement may occur within a few days to several weeks, depending on the individual[1]. 

Is doxazosin safe during pregnancy or breastfeeding? 

There isn’t currently enough data to confirm the safety of taking doxazosin during pregnancy or breastfeeding. If you are pregnant, planning to become pregnant, or breastfeeding, discuss alternative treatments with your doctor[1]. 

For the official NHS guide to doxazosin, visit their website.