Doxazosin Tablets

High blood pressure and benign prostatic hyperplasia (BPH) are common conditions in adults that can be managed effectively with appropriate treatment. Doxazosin tablets are a prescription alpha-1 adrenoceptor blocker used to treat hypertension in adults and to relieve the urinary symptoms associated with BPH in men. Standard-release doxazosin tablets require careful initiation: the first dose must be 1mg taken at bedtime to reduce the risk of a significant fall in blood pressure on standing. Dose increases are made gradually over several weeks. Available in strengths of 1mg, 2mg, and 4mg, doxazosin tablets are taken once daily. A prescription can only be issued following a clinical consultation with a registered prescriber.

Doxazosin tablets are an oral prescription medicine containing doxazosin mesilate as the active ingredient. Doxazosin belongs to the alpha-1 adrenoceptor blocker class of medicines. It is a selective alpha-1 blocker with no significant alpha-2 activity, which means it produces vasodilation without the reflex tachycardia (rapid heart rate) associated with non-selective alpha blockers.

Standard-release doxazosin tablets are licensed in the United Kingdom for two indications: the treatment of hypertension and the treatment of signs and symptoms of benign prostatic hyperplasia. Unlike the modified-release formulation, which uses a GITS delivery system and can be started at 4mg, standard-release doxazosin must be initiated at 1mg to minimise the risk of first-dose hypotension. The dose is then increased gradually over several weeks depending on clinical response and tolerability.

All clinical information on this page is drawn from the current UK Summary of Product Characteristics for doxazosin 1mg, 2mg, and 4mg tablets.

Important — first dose and postural hypotension: Standard-release doxazosin carries a significant risk of a sudden fall in blood pressure, particularly with the first dose and after each dose increase. The first dose must always be 1mg taken at bedtime. Take the first dose immediately before going to sleep and do not get up in the night unless necessary. Rise slowly from bed in the morning. This precaution applies each time your dose is increased.

Doxazosin works by selectively blocking alpha-1 adrenoceptors, which are found in the smooth muscle of blood vessel walls and in the prostate gland and bladder neck.

Effect on Blood Pressure

Alpha-1 adrenoceptors in blood vessel walls are stimulated by noradrenaline, causing vasoconstriction (narrowing of blood vessels). By blocking these receptors, doxazosin causes vasodilation (widening of blood vessels), reducing peripheral vascular resistance and lowering blood pressure. Unlike beta blockers, doxazosin does not reduce heart rate. Unlike diuretics, it does not reduce fluid volume. Its mechanism is therefore complementary to other antihypertensive medicines and doxazosin is commonly prescribed as an add-on therapy when other antihypertensives alone have not achieved adequate blood pressure control.

Effect on Benign Prostatic Hyperplasia

In BPH, an enlarged prostate causes the smooth muscle around the urethra to become tense, obstructing urinary flow. Alpha-1 adrenoceptors control this smooth muscle tone. By blocking them, doxazosin relaxes the muscles of the prostate and bladder neck, reducing the obstruction and improving urinary symptoms including difficulty starting, poor flow, incomplete emptying, frequency, and urgency. The effect on urinary symptoms is usually noticeable within one to two weeks of starting treatment at an effective dose.

First-Dose Hypotension

Because standard-release doxazosin is absorbed relatively rapidly, the first dose and each dose increase can cause a sudden and significant fall in blood pressure, particularly when standing (postural hypotension). This is why the first dose must be 1mg taken at bedtime, so that the patient is lying down while the blood level peaks and the blood pressure-lowering effect is at its greatest. After several doses, tolerance to this first-dose effect develops, and the risk of postural hypotension reduces.

Always take doxazosin exactly as your prescriber instructs. The dosing schedule for standard-release doxazosin differs importantly from the modified-release formulation. Read the Patient Information Leaflet supplied with your medicine before starting treatment.

• The first dose of doxazosin must always be 1mg, taken at bedtime. Take it immediately before you get into bed and do not get up in the night unless essential. This minimises the risk of a fall in blood pressure on standing after the first dose.
• After the first dose, doxazosin can be taken at any time of day, once daily. Your prescriber will advise on the best timing for you. Many patients take it at bedtime throughout treatment.
• Doxazosin tablets can be taken with or without food.
• The tablets are scored and may be halved if your prescriber instructs you to do so.
• Take the same care with the first tablet at each dose increase as you did with the very first dose. Each time your dose is increased, take the first higher-dose tablet at bedtime.
• If you miss a dose, take it as soon as you remember. If it is nearly time for your next dose, skip the missed dose and continue with your normal schedule. Do not take two doses at the same time.
• Do not stop taking doxazosin without speaking to your prescriber first. Stopping suddenly may cause your blood pressure to rise or urinary symptoms to return.

Doxazosin standard-release tablets are available in three strengths through this service: 1mg, 2mg, and 4mg. The appropriate dose will be determined by your prescriber. Because of the first-dose hypotension risk, all patients must begin at 1mg and dose increases are made gradually.

Doxazosin 1mg Tablets

The 1mg tablet is the mandatory starting dose for all patients beginning standard-release doxazosin. It is taken once daily at bedtime. After one to two weeks, if blood pressure or urinary symptoms are not adequately controlled and the 1mg dose has been tolerated without significant postural symptoms, the dose may be increased to 2mg on your prescriber's advice. The 1mg tablet is also used at the start of each dose escalation step, as each new higher dose carries a similar first-dose hypotension risk and should be started at bedtime.

Doxazosin 2mg Tablets

The 2mg tablet is an intermediate dose used during dose titration. It may be prescribed after an adequate period at 1mg if further blood pressure reduction or improvement in BPH symptoms is needed. For BPH, a dose of 2mg once daily provides meaningful symptom relief for many patients. For hypertension, 2mg may represent a suitable maintenance dose for patients who do not need the full 4mg.

Doxazosin 4mg Tablets

The 4mg tablet is the commonly used maintenance dose for both hypertension and BPH. For hypertension, doxazosin 4mg once daily provides effective blood pressure control in many patients when used alongside other antihypertensives. For BPH, doses up to 8mg may be used in some patients, achieved by titrating with additional tablets. The maximum recommended dose for hypertension is 16mg daily, though doses above 4mg are less commonly required. All dose adjustments are made by your prescriber. The first tablet at each new dose must be taken at bedtime.

Like all medicines, doxazosin tablets can cause side effects, although not everyone experiences them. The information below is based on the current UK SmPC. Refer to the Patient Information Leaflet for the full list.

Common Side Effects (may affect up to 1 in 10 people)

• Dizziness or lightheadedness, particularly when standing up quickly (postural hypotension). This is most likely after the first dose, after each dose increase, and in patients who are dehydrated.
• Headache.
• Fatigue and tiredness.
• Oedema (swelling of the ankles, feet, or legs).
• Palpitations (awareness of the heartbeat).
• Nausea or gastrointestinal discomfort.

Uncommon Side Effects (may affect up to 1 in 100 people)

• Low blood pressure (hypotension).
• Urinary incontinence, particularly in women.
• Dry mouth.
• Skin rash or itching.
• Sleep disturbance.

Serious Side Effects: Seek Urgent Medical Attention

Contact your prescriber or go to your nearest accident and emergency department promptly if you experience any of the following:

• Prolonged or painful erection (priapism) - this is a rare but serious side effect of alpha blockers that requires immediate medical attention. If not treated promptly, priapism can cause permanent damage.
• Severe dizziness or fainting, particularly when standing. If you fall or injure yourself as a result of dizziness, seek medical attention.
• Signs of a serious allergic reaction, such as sudden swelling of the face, lips, tongue, or throat; difficulty breathing; or a severe skin reaction.
• Intraoperative floppy iris syndrome - if you are due to have cataract surgery or other eye surgery, inform your ophthalmologist that you are taking or have previously taken doxazosin. This must be disclosed before any ophthalmic procedure, as the risk persists even after doxazosin has been stopped.

Report any suspected side effect to your prescriber or pharmacist or via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk.

Doxazosin Tablets May Be Suitable If You:

• Are an adult with hypertension who requires an additional antihypertensive medicine, particularly as an adjunct to existing treatment.
• Are an adult male with lower urinary tract symptoms associated with BPH who requires treatment.
• Are already prescribed doxazosin standard-release tablets and require a repeat prescription through an online prescribing service.

Doxazosin Tablets Are Not Suitable If You:

• Have a history of postural hypotension or are at high risk of falls from low blood pressure.
• Have severe liver impairment, as doxazosin is extensively metabolised in the liver.
• Are being treated for hypertension with monotherapy and have had heart failure or a history of orthostatic hypotension.
• Have a known allergy to doxazosin, other quinazoline derivatives (such as prazosin or terazosin), or any excipient listed in the SmPC.
• Are under 18 years of age (this service is for adults only).

Cautions

Particular care is required in older patients, who are at greater risk of postural hypotension and falls. Patients with liver impairment should be monitored, as doxazosin is extensively metabolised in the liver and dose reduction may be needed. As with doxazosin modified release, any patient planning eye surgery must inform their ophthalmologist of current or previous alpha-blocker use due to the risk of intraoperative floppy iris syndrome. Patients taking other antihypertensive medicines are at greater risk of a significant blood pressure fall, particularly with the first dose.

Important Drug Interactions

Doxazosin can interact with a number of commonly prescribed medicines. Tell your prescriber about all medicines you take, including over-the-counter products and supplements. The following interactions are of particular clinical importance:

• Other antihypertensive medicines: the blood pressure-lowering effect of doxazosin is significantly enhanced when combined with other antihypertensives, including calcium channel blockers, ACE inhibitors, ARBs, beta blockers, and diuretics. Extra caution with the first dose is required in patients already taking other blood pressure medicines.
• PDE-5 inhibitors (such as sildenafil, tadalafil, and vardenafil): combining alpha blockers with PDE-5 inhibitors can cause a significant and potentially dangerous fall in blood pressure. Seek medical advice before combining these medicines.
• NSAIDs such as ibuprofen: these can reduce the antihypertensive effect of doxazosin.
• Other alpha blockers used for BPH (such as tamsulosin, alfuzosin): combining doxazosin with another alpha blocker significantly increases the risk of hypotension.

This is not a complete list of interactions. Your prescriber will carry out a full clinical assessment, including a review of your current medicines, before any prescription is considered.

Doxazosin tablets are a prescription-only medicine. The clinical consultation is the essential first step. A prescription will only be issued if a registered prescriber determines, based on their individual assessment of your circumstances, that doxazosin is clinically appropriate for you.

During your online consultation with Pharmacy Planet, a registered prescriber will review your clinical information. This includes your blood pressure readings, relevant medical history, current medicines, and any urinary symptoms if BPH is the indication. The prescriber will also assess whether standard-release doxazosin is the most appropriate formulation or whether the modified-release version would be more suitable. For new patients, the prescribing process will include guidance on the bedtime first-dose requirement.

Not all consultations will result in a prescription being issued. The prescriber may recommend a different dose, the modified-release formulation, or suggest that a face-to-face appointment with your GP or urologist is more appropriate. This process is designed to ensure your safety.

If you are already being managed for hypertension or BPH by your GP or a specialist, please keep them informed of all medicines you are taking, including any prescribed through online services.

• Store below 30°C.
• Store in the original packaging to protect from light and moisture.
• Keep out of the sight and reach of children.
• Do not use after the expiry date printed on the packaging.
• Do not dispose of medicines via household waste or wastewater. Return unused or out-of-date tablets to your pharmacist for safe disposal.

Full storage instructions are provided in the Patient Information Leaflet supplied with your medicine.

The table below compares the two doxazosin formulations available at Pharmacy Planet. Both are alpha-1 adrenoceptor blockers used for high blood pressure and, in men, for symptoms of benign prostatic hyperplasia.

Important: This comparison is for general information only and does not replace medical advice. A prescriber will decide which treatment is suitable for you following an online consultation.

Pharmacy Planet is a GPhC-registered online pharmacy providing access to prescription medicines through a clinically led consultation process. Our registered prescribers and pharmacists are committed to patient safety, clinical accuracy, and responsible prescribing.

We follow GPhC standards, MHRA guidance, and ASA advertising regulations in all aspects of our service. Every prescription is reviewed and dispensed by qualified healthcare professionals. We provide clear, factual information to help patients understand their antihypertensive medication and make informed decisions about their health.

If you have questions about doxazosin tablets, alpha blocker therapy, or cardiovascular or urological health, our pharmacy team is available to help. We are committed to transparent, patient-centred care.

References

1. Electronic Medicines Compendium (eMC). Doxazosin 1mg, 2mg and 4mg Tablets — Summary of Product Characteristics. https://www.medicines.org.uk/emc. Accessed August 2026.
2. National Institute for Health and Care Excellence (NICE). Hypertension in adults: diagnosis and management. NICE guideline NG136. https://www.nice.org.uk/guidance/ng136. Accessed August 2026.
3. NHS. Doxazosin. https://www.nhs.uk/medicines/doxazosin. Accessed August 2026.
4. Joint Formulary Committee. British National Formulary (BNF). Doxazosin. BMJ Group and Pharmaceutical Press. https://bnf.nice.org.uk. Accessed August 2026.
5. Medicines and Healthcare products Regulatory Agency (MHRA). Yellow Card — report a side effect. https://yellowcard.mhra.gov.uk. Accessed August 2026.