Cardugen contains doxazosin 4 mg, an alpha-blocker. It treats high blood pressure and, more commonly, the urinary symptoms of an enlarged prostate — a weak stream, hesitancy and getting up at night. The first dose can cause marked dizziness, so it is taken at bedtime.
What is Cardugen?
Cardugen contains doxazosin (sometimes written doxazocin), an alpha-1 adrenoceptor blocker, available as 1 mg, 2 mg and 4 mg tablets and as an extended-release form. It is a Schedule 3 medicine.
Alpha-1 receptors sit on smooth muscle in two places that matter here: the walls of arteries, and the neck of the bladder and the prostate. Noradrenaline acting on those receptors makes the muscle contract. Doxazosin blocks them, so the muscle relaxes.
That single action produces both of its uses. In arteries, relaxation widens the vessel and lowers blood pressure. In the prostate and bladder neck, relaxation opens the outflow so urine passes more freely.
For benign prostatic hyperplasia (BPH) this is worth understanding properly. The prostate sits around the urethra, and as it enlarges with age it squeezes that tube. But the obstruction has two components: the bulk of the enlarged gland, and the muscle tone within it and the bladder neck. Doxazosin does nothing about the bulk — it relaxes the muscle tone, which is often enough to improve the stream substantially.
That is why it works within days, while medicines that shrink the prostate take months.
What is Cardugen commonly used for?
- Benign prostatic hyperplasia (BPH) — a weak or slow urinary stream, hesitancy starting, dribbling at the end, incomplete emptying, urgency, and waking at night to pass urine. This is its commonest use.
- High blood pressure, usually as an add-on where other medicines have not achieved control.
- Resistant hypertension, as a fourth or later agent.
- Phaeochromocytoma, a rare adrenal tumour, in specialist use.
For BPH, expect improvement within a few days to two weeks. If it helps, it is generally continued long term.
A common combination is doxazosin with finasteride or dutasteride, which shrink the prostate over six to twelve months. The alpha-blocker gives quick relief while the other works slowly on the underlying enlargement.
Urinary symptoms in men need proper assessment first. They are usually BPH, which is benign — but prostate cancer, a urinary infection, bladder stones and neurological conditions can present the same way. A doctor will examine the prostate, test urine, and often check a PSA blood test. Treating symptoms without that assessment risks missing something, and a PSA should generally be checked before starting treatment, since alpha-blockers do not affect PSA but the assessment matters.
For blood pressure, doxazosin is not a first-line choice — calcium channel blockers such as amlodipine, ACE inhibitors such as enalapril and thiazide diuretics such as Ridaq come first. It is added when those have not been enough.
How Cardugen fits into this medicine category
| Group | Examples | Role |
|---|---|---|
| Alpha-blockers | Doxazosin (Cardugen), tamsulosin, terazosin | BPH symptoms; add-on for blood pressure |
| 5-alpha reductase inhibitors | Finasteride, dutasteride | Shrinks the prostate over months |
| Calcium channel blockers | Amlodipine (Ciplavasc) | First-line blood pressure |
| ACE inhibitors / ARBs | Enalapril, losartan | First-line blood pressure |
| Diuretics | Hydrochlorothiazide (Ridaq) | First-line blood pressure |
Tamsulosin is more selective for the prostate and lowers blood pressure less, so it is often preferred for BPH alone — while doxazosin suits someone who needs both problems treated. See the heart, blood pressure and circulation medicines hub.
What to check before using Cardugen
Take the first dose at bedtime, and be careful getting up during that night. This is the key practical instruction. Alpha-blockers can cause a pronounced drop in blood pressure with the first dose — the “first-dose effect” — producing dizziness or even fainting. Taking it lying down in bed avoids a fall.
Rise slowly from lying or sitting, particularly in the first days and after any increase.
Tell your prescriber or pharmacist if:
- You have low blood pressure, or faint or feel dizzy on standing.
- You have heart failure, or a heart valve problem.
- You have liver disease.
- You are due cataract surgery, or may be. Alpha-blockers cause intraoperative floppy iris syndrome, which complicates the operation — tell your eye surgeon you take it, even if you stopped some time ago. This is easily forgotten and genuinely matters.
- You take other blood pressure medicines, or a PDE5 inhibitor such as sildenafil or tadalafil — the combination can drop blood pressure sharply, and timing needs discussing.
- You have a history of fainting on passing urine.
Do not restart at your usual amount after a break of several days — the first-dose effect returns. Ask your prescriber.
Follow the dispensing label. This page does not set doses.
Possible cautions and when to ask a pharmacist or doctor
Dizziness and light-headedness are the commonest effects, particularly early and on standing. They usually ease as the body adjusts.
Tell your eye surgeon. Floppy iris syndrome during cataract surgery is the caution most often missed, and it is one an ophthalmologist can plan around if told in advance.
Report worsening urinary symptoms rather than continuing. Inability to pass urine at all is a medical emergency — go to hospital.
Report blood in the urine, pain on passing urine, or unintended weight loss, which need investigation rather than symptom treatment.
Nasal congestion, tiredness and headache are common.
Ejaculation changes can occur, more so with tamsulosin than doxazosin. Worth mentioning if it bothers you, as alternatives exist.
Priapism — a painful erection lasting more than four hours — is rare but a medical emergency requiring immediate treatment to prevent permanent damage.
Seek urgent medical attention for fainting or collapse, inability to pass urine, a painful erection lasting more than four hours, chest pain, palpitations, or marked swelling of the ankles with breathlessness. Seek assessment for blood in the urine, pain on passing urine, fever with urinary symptoms, or symptoms that are worsening.
Related medicine guides
- Browse Heart, Blood Pressure & Circulation Medicines guides
- Read: Ciplavasc used for
- Read: Ridaq used for
Frequently asked questions
What is Cardugen 4 mg used for? Mainly the urinary symptoms of an enlarged prostate — weak stream, hesitancy, night-time waking — and also high blood pressure as an add-on. It contains doxazosin.
How quickly does it work for prostate symptoms? Usually within a few days to two weeks, because it relaxes muscle tone rather than shrinking the prostate.
Does it shrink the prostate? No. That requires a different medicine such as finasteride, which takes six to twelve months. The two are often used together.
Why must I take the first dose at bedtime? Alpha-blockers can cause a marked drop in blood pressure with the first dose. Taking it in bed avoids dizziness or a fall.
I am having cataract surgery. Does it matter? Yes — tell your eye surgeon you take it, even if you have stopped. Alpha-blockers cause floppy iris syndrome, which the surgeon can plan around if told.
Can I take it with sildenafil? Discuss it with your doctor first. Together they can drop blood pressure sharply, and the timing needs planning.