Tamsulosin side effects: a complete guide

Tamsulosin relaxes the smooth muscle in the prostate and bladder neck, making it easier to pass urine.

Because alpha-1 receptors are found throughout the body, the medicine can cause effects beyond the urinary tract.

Common side effects (affecting up to 1 in 10 people):

• Dizziness: the most frequently reported side effect, caused by a drop in blood pressure when standing (orthostatic hypotension)
• Abnormal ejaculation: including reduced semen volume or retrograde ejaculation, reported in up to 10% of men
• Nasal congestion or runny nose: due to relaxation of blood vessels in the nasal passages
• Headache: usually mild and short-lived

According to the BNF, these effects are generally dose-related and most noticeable during the first few days of treatment. Taking tamsulosin after a meal can help reduce the risk of dizziness.

The standard dose is 400 micrograms once daily, and dose adjustment is not usually required.

Some side effects of tamsulosin occur less frequently but are still worth knowing about.

• Palpitations or fast heartbeat: due to reflex tachycardia in response to blood pressure changes
• Nausea, vomiting or diarrhoea: mild gastrointestinal effects that usually pass within the first week
• Constipation: occasionally reported
• Skin rash or itching: an uncommon allergic-type reaction
• Weakness or fatigue: related to the blood-pressure-lowering effect
• Blurred vision: generally transient

A particularly important effect for anyone planning eye surgery is intraoperative floppy iris syndrome (IFIS).

This is a complication that can occur during cataract surgery in patients who are taking or have previously taken tamsulosin.

The NHS and NICE advise that you should always inform your ophthalmologist if you are using or have used tamsulosin, even if you stopped taking it months or years ago.

Serious side effects of tamsulosin are rare, but prompt recognition is essential.

Severe hypotension (very low blood pressure):

Symptons include feeling very dizzy or faint, particularly on standing. This is most likely with the first dose or if tamsulosin is combined with other blood-pressure-lowering medicines.

Sit or lie down immediately and call your GP or 111.

Priapism:

A prolonged, painful erection lasting more than 4 hours is a medical emergency. Without treatment, priapism can cause permanent damage. Go to A&E immediately.

Severe allergic reaction (angioedema):

Swelling of the face, lips, tongue or throat with difficulty breathing requires emergency treatment. Call 999 without delay.

Stevens-Johnson syndrome:

Very rarely, tamsulosin has been associated with severe skin reactions. Seek urgent medical help if you develop widespread blistering of the skin, mouth or eyes.

The BNF recommends that patients who experience recurrent dizziness or syncope should be reviewed and the medicine reconsidered.

Changes in ejaculation are one of the most discussed side effects of tamsulosin, and they can understandably cause concern.

Tamsulosin relaxes the smooth muscle of the bladder neck, which normally closes during ejaculation to direct semen outward.

When this muscle is relaxed, semen may travel backwards into the bladder instead. This is known as retrograde ejaculation and is the reason some men notice reduced or absent ejaculate.

Key points to understand:

• Retrograde ejaculation is not harmful and does not cause pain or health problems
• The semen is simply passed out of the body the next time you urinate
• It occurs in approximately 5 to 10% of men taking tamsulosin
• It is reversible and typically resolves within a few days of stopping the medicine
• It can affect fertility, so discuss this with your doctor if you are planning to conceive

If ejaculation changes are a significant concern, your doctor may consider an alternative alpha-blocker such as alfuzosin, which has a lower incidence of this effect.

However, tamsulosin remains the most commonly prescribed alpha-blocker for BPH on the NHS because of its overall efficacy and tolerability profile.

Most side effects of tamsulosin can be managed with simple practical measures.

For dizziness and low blood pressure:

• Take tamsulosin about 30 minutes after a meal (usually after breakfast or the evening meal)
• Stand up slowly from sitting or lying positions
• Avoid alcohol, which can compound the blood-pressure-lowering effect
• Stay well hydrated

For nasal congestion:

• Over-the-counter saline nasal sprays can provide relief
• Avoid decongestant sprays containing pseudoephedrine, as these may counteract the effect of tamsulosin

For headache:

• Paracetamol is safe to take alongside tamsulosin
• Avoid regular use of ibuprofen unless approved by your doctor, as NSAIDs can affect blood pressure

Before cataract surgery:

• Inform your eye surgeon well in advance that you take or have taken tamsulosin
• Your surgeon may want to plan for IFIS during the procedure

If side effects persist beyond the first 2 weeks or significantly affect your quality of life, speak to your GP about adjusting your treatment.

For more on correct dosing, see our tamsulosin dosage guide.

While most tamsulosin side effects are mild, some situations require prompt medical attention.

Speak to your GP or call 111 if you experience:

• Persistent dizziness or repeated episodes of feeling faint
• A rash that is spreading or accompanied by itching
• Difficulty breathing that is new or worsening
• Significant changes in urinary symptoms that may suggest the medicine is not working

Go to A&E or call 999 if you experience:

• A prolonged, painful erection lasting more than 4 hours (priapism)
• Swelling of the face, lips or tongue with difficulty breathing
• Severe blistering of the skin, mouth or eyes
• Fainting or collapse

The NHS recommends carrying on with tamsulosin even if you feel well, as it controls symptoms rather than curing the underlying condition.

If treatment is to be stopped, your doctor will advise you on the safest way to do so.