Tamsulosin dosage guide: how much to take and when

The BNF recommends the following dosage for tamsulosin in the management of lower urinary tract symptoms associated with benign prostatic hyperplasia.

Standard dose:

• 400 micrograms (0.4 mg) once daily, taken approximately 30 minutes after a meal
• The medicine is available as a modified-release capsule, which means it releases the active ingredient slowly over the course of the day
• The capsule should be swallowed whole and not opened, chewed or crushed, as this would damage the modified-release mechanism

Key points:

• Unlike many medicines, tamsulosin does not require dose titration. You start at the full dose from day one
• There is no need to adjust the dose for elderly patients
• The same 400 microgram dose is used regardless of the severity of symptoms
• Tamsulosin is usually taken long-term, as symptoms return when the medicine is stopped

The reason tamsulosin is taken after food is that food slows its absorption, producing a smoother blood-level curve and reducing the risk of dizziness and orthostatic hypotension.

Tamsulosin is sometimes prescribed off-label to help pass small kidney stones (ureteric calculi).

This use, known as medical expulsive therapy, takes advantage of tamsulosin's ability to relax smooth muscle in the ureter.

Dosage for kidney stones:

• 400 micrograms once daily (the same dose used for BPH)
• Treatment is typically given for 2 to 4 weeks or until the stone has passed
• It is most effective for stones in the lower third of the ureter that are 5 to 10 mm in size

NICE guidelines (NG196) recommend offering an alpha-blocker to adults with distal ureteric stones that are expected to pass spontaneously.

The evidence is strongest for tamsulosin, which has been shown to increase the spontaneous stone passage rate and reduce the time to passage.

Important considerations:

• Tamsulosin for kidney stones is an off-label use in the UK
• Patients should be counselled about the side effects, particularly dizziness
• Adequate hydration is important alongside the medicine
• If the stone does not pass within 4 weeks, surgical options should be discussed

The timing of your tamsulosin dose matters more than with many other medicines because of its effect on blood pressure.

Recommended timing:

• Take your capsule approximately 30 minutes after the same meal each day
• Most men choose to take it after breakfast, but after the evening meal is equally acceptable
• Consistency is important: pick a time and stick to it

Why timing matters:

• Taking tamsulosin on an empty stomach causes the medicine to be absorbed more quickly, which increases the peak blood level and raises the risk of dizziness
• Taking it after food smooths out the absorption profile
• A consistent daily routine makes it less likely that you will forget a dose

If you work shifts or have irregular mealtimes:

• Choose the meal you eat most consistently
• Set a daily alarm on your phone as a reminder
• If your schedule changes, take the capsule after the next substantial meal

Your pharmacist can provide a dosette box or blister pack if you take multiple medicines and find it hard to keep track.

If you forget to take your tamsulosin capsule, the advice depends on how long ago you should have taken it.

NHS guidance on missed doses:

• If you remember on the same day: take it after your next meal and then continue as normal the following day
• If you do not remember until the next day: skip the missed dose and take the next one at your usual time
• Never take a double dose to make up for a missed one, as this increases the risk of dizziness and low blood pressure

What happens if you miss several doses?

Tamsulosin does not build up in the body in the way some medicines do. If you have missed several days, you can restart at the same 400 microgram dose without needing to re-titrate.

However, be aware that dizziness may recur when you restart, just as it might with a new course.

Practical tips to avoid missing doses:

• Link your dose to a daily habit, such as brushing your teeth after breakfast
• Use a pill organiser or pharmacy blister pack
• Ask your pharmacist about the NHS Electronic Repeat Dispensing service, which ensures your prescription is ready on time

One of the advantages of tamsulosin is that dose adjustment is rarely needed, even in populations that often require careful dosing.

Elderly patients:

• No dose reduction is needed in older adults
• However, extra care should be taken regarding falls risk, as dizziness and orthostatic hypotension can be more pronounced
• The NICE falls prevention guidelines (CG161) recommend reviewing alpha-blockers in patients with a history of falls

Renal impairment:

• No dose adjustment is required for mild to moderate kidney disease
• In severe renal impairment (creatinine clearance below 10 ml/min), tamsulosin is not recommended as there is limited safety data

Hepatic impairment:

• No dose adjustment is needed for mild to moderate liver disease
• Tamsulosin should be avoided in severe hepatic impairment

Interactions that may affect dosing:

• Strong CYP3A4 inhibitors (such as ketoconazole) and strong CYP2D6 inhibitors (such as paroxetine) can increase tamsulosin blood levels; the BNF advises caution with these combinations
• Other alpha-blockers should not be used concurrently (risk of severe hypotension)
• PDE5 inhibitors (such as sildenafil or tadalafil): extra caution is needed as both lower blood pressure

Unlike some medicines, tamsulosin does not usually require a gradual dose reduction before stopping.

Key points about stopping:

• Urinary symptoms will typically return within 1 to 2 weeks of stopping the medicine
• There is no withdrawal syndrome or rebound effect
• If you are stopping because of side effects, discuss alternatives with your doctor; other alpha-blockers such as alfuzosin or doxazosin may be better tolerated
• If you are stopping before cataract surgery, be aware that intraoperative floppy iris syndrome (IFIS) can still occur even after stopping tamsulosin

When your doctor might stop tamsulosin:

• If your symptoms are well controlled and you are also taking a 5-alpha reductase inhibitor (such as finasteride or dutasteride), your doctor may trial stopping tamsulosin after 6 months of combination therapy
• If you have had prostate surgery (such as TURP), the underlying obstruction is resolved and tamsulosin is usually no longer needed
• If side effects outweigh the benefits

Always discuss stopping or changing your tamsulosin with your doctor before making any changes to your treatment.