Cardura

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Cardura on Prescriptsy

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Cardura is a branded medicine containing doxazosin mesilate, an alpha-1 adrenoceptor blocker licensed in the United Kingdom for the treatment of essential hypertension and the symptomatic management of benign prostatic hyperplasia (BPH).

Doxazosin relaxes smooth muscle in blood vessel walls and in the prostate gland, producing a dual therapeutic effect: lowering blood pressure and improving urinary flow in men with prostatic enlargement.

Hypertension affects approximately 1 in 3 adults in England, while BPH is present in roughly half of men over 50.

Doxazosin occupies a particular niche in UK clinical practice as one of the few antihypertensive medicines that also treats lower urinary tract symptoms (LUTS) associated with BPH, making it useful for men who have both conditions.

This page provides a comprehensive clinical overview of how Cardura works, dosing for hypertension and BPH, the difference between standard and modified-release formulations, side effects, safety warnings, and how to obtain a prescription in the UK.

Important safety information about Cardura

Before reading further, note the following key safety points regarding Cardura.

• Cardura can cause significant postural hypotension (a drop in blood pressure on standing), particularly with the first dose or after dose increases. Take the first dose of standard Cardura at bedtime.
• If you are planning cataract surgery, inform your ophthalmologist that you are taking or have previously taken an alpha-blocker, as intraoperative floppy iris syndrome (IFIS) has been associated with these medicines.
• Seek emergency medical help (call 999) if you experience a prolonged, painful erection (priapism).
• Cardura may interact with PDE5 inhibitors (sildenafil, tadalafil), causing additive blood pressure-lowering effects.

Understanding hypertension and BPH

Hypertension

Hypertension is persistently elevated blood pressure that increases the risk of cardiovascular disease, stroke, heart failure, chronic kidney disease, and vascular dementia.

It is usually asymptomatic and detected during routine health assessments.

NICE defines hypertension as a clinic blood pressure of 140/90 mmHg or higher, confirmed by ambulatory or home blood pressure monitoring (threshold 135/85 mmHg).

Treatment with antihypertensive medicines substantially reduces the risk of cardiovascular events.

Benign prostatic hyperplasia

BPH is a non-cancerous enlargement of the prostate gland that compresses the prostatic urethra and causes lower urinary tract symptoms (LUTS).

These include hesitancy, a weak or intermittent urinary stream, incomplete bladder emptying, increased urinary frequency, nocturia, urgency, and terminal dribbling.

BPH is strongly age-related, affecting approximately 50% of men over 50 and up to 80% of men over 70.

Whilst not life-threatening, BPH significantly impairs quality of life and can lead to complications including acute urinary retention, recurrent urinary tract infections, and bladder stone formation.

How Cardura works: mechanism of action

Doxazosin is a selective, competitive antagonist of the alpha-1 adrenoceptor. Alpha-1 receptors are found on vascular smooth muscle, the prostate capsule, the prostatic urethra, and the bladder neck.

Noradrenaline released from sympathetic nerves acts on these receptors to contract smooth muscle.

In blood vessels, alpha-1 receptor blockade produces vasodilation of both arterioles and venules, reducing total peripheral vascular resistance and lowering blood pressure.

Doxazosin is relatively selective for the alpha-1 subtype and does not cause significant tachycardia or renin release, distinguishing it from older non-selective alpha-blockers such as prazosin.

In the prostate, alpha-1 receptors (predominantly the alpha-1A subtype) mediate smooth muscle contraction in the prostatic capsule, stroma, and bladder neck.

Blockade of these receptors reduces the dynamic component of bladder outflow obstruction, improving urinary flow rate and relieving symptoms of BPH.

Alpha-blockers act relatively quickly, with many patients noticing symptom improvement within days to weeks, in contrast to 5-alpha reductase inhibitors (such as finasteride or dutasteride), which require months to reduce prostate volume.

Doxazosin also has a modest, beneficial effect on plasma lipid profiles. It reduces total cholesterol and low-density lipoprotein (LDL) cholesterol and slightly increases high-density lipoprotein (HDL) cholesterol.

While the clinical significance of this effect is not established, it is a favourable ancillary property in patients with concomitant dyslipidaemia.

Clinical evidence and NICE guidance

Hypertension

NICE Guideline NG136 positions alpha-blockers as step 4 antihypertensive therapy for resistant hypertension (blood pressure not controlled on optimal doses of an ACE inhibitor or ARB, a calcium channel blocker, and a thiazide-like diuretic).

The ALLHAT trial (2002) found that doxazosin was associated with a higher risk of heart failure compared with chlorthalidone as first-line monotherapy, leading to the doxazosin arm being discontinued early.

As a result, alpha-blockers are no longer recommended as first-line or second-line monotherapy for hypertension.

However, doxazosin remains a useful add-on agent in resistant hypertension, particularly when combined with other classes.

The ASCOT-BPLA study showed that adding doxazosin GITS as a third- or fourth-line agent to patients with uncontrolled hypertension produced further significant blood pressure reductions.

NICE recommends considering an alpha-blocker, a beta-blocker, or spironolactone at step 4 for resistant hypertension, based on the individual patient's profile.

Benign prostatic hyperplasia

NICE Clinical Guideline NG45 recommends offering an alpha-blocker to men with moderate to severe LUTS when conservative management (lifestyle advice, bladder training) has been insufficient.

Alpha-blockers provide rapid symptom relief and are suitable as first-line pharmacological therapy.

For men with larger prostates (estimated above 30 g or PSA above 1.4 ng/mL), combination therapy with a 5-alpha reductase inhibitor may be more appropriate.

Doxazosin is one of the alpha-blockers recommended in the BNF alongside tamsulosin and alfuzosin.

Standard tablets versus modified-release (XL)

Cardura is available in two formulations. Standard tablets (1 mg, 2 mg, 4 mg) release doxazosin immediately, producing peak plasma concentrations within 2 to 3 hours.

The dose must be titrated gradually from 1 mg to minimise first-dose hypotension.

Cardura XL (4 mg, 8 mg) uses a gastrointestinal therapeutic system (GITS) that releases doxazosin at a controlled rate over approximately 24 hours.

This produces a flatter pharmacokinetic profile with lower peak-to-trough variation, reducing the incidence and severity of postural hypotension and allowing treatment to start at 4 mg without the need for slow titration from 1 mg.

The two formulations are not interchangeable on a milligram-for-milligram basis.

A patient on standard doxazosin 4 mg daily should switch to Cardura XL 4 mg daily under prescriber guidance.

Modified-release tablets must be swallowed whole and must not be crushed, chewed, or divided.

Dosage and administration

Hypertension

Standard Cardura: start at 1 mg once daily (at bedtime), increase to 2 mg after 1 to 2 weeks, then to 4 mg if needed.

Maximum dose 16 mg daily. Cardura XL: start at 4 mg once daily, increase to 8 mg if needed after 4 weeks.

Benign prostatic hyperplasia

Standard Cardura: start at 1 mg once daily, titrate to 2 mg, then 4 mg, and up to 8 mg daily at 1 to 2-week intervals based on symptom response.

Cardura XL: usual dose 4 mg once daily, increased to 8 mg if required.

Missed doses and treatment interruption

If a dose is missed, take the next dose at the usual time. Do not take a double dose.

If treatment is interrupted for several days or more, re-initiation at the starting dose is recommended because tolerance to the first-dose hypotensive effect may be lost.

Side effects of Cardura

Common side effects

The most common adverse effects are dizziness, light-headedness, postural hypotension, headache, and fatigue. These are dose-related and are most prominent during the initial dose titration phase.

Peripheral oedema (ankle swelling), somnolence, nasal congestion, and gastrointestinal symptoms (nausea, abdominal discomfort, diarrhoea) are also reported.

Most of these effects are mild and tend to diminish over time as the body adjusts.

Uncommon and rare side effects

Uncommon side effects include dry mouth, blurred vision, urinary incontinence (particularly stress incontinence in women), weight gain, and musculoskeletal pain. Tachycardia and palpitations may occur, particularly in the presence of excessive blood pressure reduction.

Rare but important adverse effects include priapism (a prolonged, painful erection lasting more than 4 hours), which is a urological emergency requiring immediate treatment.

Hepatic reactions, including cholestatic jaundice and hepatitis, have been reported very rarely. Leucopenia and thrombocytopenia are documented in post-marketing reports.

Intraoperative floppy iris syndrome (IFIS) has been observed during cataract surgery in patients currently or previously treated with alpha-1 blockers.

The iris becomes flaccid and the pupil constricts during surgery, increasing the risk of complications. This effect may persist even after stopping the medicine.

When to seek medical advice

Contact your GP or call NHS 111 if you experience recurrent dizziness, fainting, significant ankle swelling, or new urinary symptoms.

Call 999 or attend A&E if you develop a prolonged painful erection, chest pain, signs of a severe allergic reaction, or jaundice (yellowing of the skin or eyes).

Report any suspected adverse reactions via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk .

Warnings and precautions

First-dose hypotension

The most important practical precaution with Cardura is the risk of postural hypotension, particularly with the first dose or after dose escalation.

Patients starting standard tablets should take the first dose at bedtime and be warned to stand up slowly.

Those at particular risk include elderly patients, patients taking other antihypertensives (especially diuretics), and those who are volume-depleted.

Cardura XL has a lower incidence of first-dose hypotension than standard tablets because of its controlled-release design.

Cataract surgery

If you are scheduled for or considering cataract surgery, inform your ophthalmologist that you are taking or have previously taken doxazosin.

Intraoperative floppy iris syndrome can increase the difficulty and risk of the procedure.

Your surgeon may modify their technique or choice of equipment if they are aware in advance.

Do not stop taking Cardura before surgery without medical advice, as stopping may not prevent IFIS and could worsen blood pressure or urinary symptoms.

Pregnancy and breastfeeding

Cardura is not recommended during pregnancy or breastfeeding due to insufficient safety data.

BPH is a condition affecting men, so pregnancy considerations apply primarily to the hypertension indication in women of childbearing potential.

Alternative antihypertensives with established safety in pregnancy (such as labetalol, nifedipine, or methyldopa) should be used instead.

Drug interactions

Doxazosin is metabolised by CYP3A4. Potent CYP3A4 inhibitors (ketoconazole, itraconazole, ritonavir, clarithromycin) may increase doxazosin plasma levels and the risk of hypotension.

PDE5 inhibitors (sildenafil, tadalafil, vardenafil) have additive blood pressure-lowering effects with alpha-blockers.

Patients taking both should be stabilised on the alpha-blocker before starting a PDE5 inhibitor, and a lower PDE5 inhibitor dose should be considered.

NSAIDs (ibuprofen, naproxen) may attenuate the antihypertensive effect of doxazosin.

How to get a Cardura prescription in the UK

Cardura is classified as a prescription-only medicine (POM) in the United Kingdom. It is prescribed by GPs, urologists, cardiologists, and authorised online prescribers following appropriate clinical assessment.

For hypertension, this typically includes blood pressure measurement (on at least two occasions), blood tests (renal function, electrolytes, lipids, glucose), and cardiovascular risk assessment.

For BPH, assessment includes symptom scoring (IPSS), digital rectal examination, PSA blood test, and urinalysis.

Generic doxazosin is widely available and considerably less expensive than the branded Cardura product. Your pharmacist may dispense a generic equivalent unless the prescriber has specified the brand.

The standard NHS prescription charge in England is currently 9.90 pounds per item; prescriptions are free in Scotland, Wales, and Northern Ireland.

Living with hypertension and BPH: practical management

Whilst Cardura effectively controls blood pressure and relieves urinary symptoms, lifestyle modifications complement pharmacological treatment.

For hypertension, reducing dietary salt, maintaining a healthy weight, exercising regularly, limiting alcohol, and stopping smoking all contribute to better blood pressure control.

For BPH, reducing evening fluid intake can improve nocturia, limiting caffeine and alcohol may reduce bladder irritability, and pelvic floor exercises can help with post-void dribbling.

Regular follow-up with your GP is important to monitor blood pressure response, assess BPH symptom progression, check PSA levels (to exclude prostate cancer), and review for side effects.

NICE recommends annual review for patients with stable BPH and more frequent review if symptoms change.

When to seek urgent medical advice

Contact your GP or call NHS 111 if you experience recurrent dizziness, fainting, significant worsening of urinary symptoms, or signs of urinary retention (inability to pass urine despite a full bladder).

Complete urinary retention is a medical emergency requiring catheterisation.

Call 999 or attend A&E if you develop chest pain, a prolonged painful erection (priapism), difficulty breathing, sudden severe headache, or signs of a severe allergic reaction (swelling of the face, lips, tongue, or throat).

Report any suspected adverse reactions via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk .

Sources

• Cardura (doxazosin), Summary of Product Characteristics (EMC)
• Doxazosin, British National Formulary (BNF)
• NICE NG136: Hypertension in adults, diagnosis and management
• NICE NG45: Lower urinary tract symptoms in men, management
• Benign prostate enlargement, NHS
• High blood pressure (hypertension), NHS
• MHRA Yellow Card Scheme