Tamdura Long-Term Side Effects: PSA, Prostate Size and PVR

What Exactly Is Tamdura?

Tamdura is a fixed combination of:

• tamsulosin 0.4 mg — an alpha-1 blocker; and
• dutasteride 0.5 mg — a 5-alpha-reductase inhibitor.

The two medicines have different jobs.

Tamsulosin

Tamsulosin relaxes smooth muscle in the prostate and bladder neck. It can improve urinary flow and symptoms relatively quickly, often within days to weeks.

It does not substantially shrink the prostate and does not lower PSA by 50%.

Dutasteride

Dutasteride blocks both major forms of 5-alpha-reductase, reducing conversion of testosterone into dihydrotestosterone (DHT).

DHT is an important driver of prostate growth. Over time, dutasteride can:

• reduce prostate volume;
• improve urinary symptoms and flow;
• reduce the risk of acute urinary retention; and
• reduce the likelihood of needing BPH surgery.

See our BPH medication guide.

Are Your Results What We Would Expect From Dutasteride?

Yes. They are quite consistent with a response to treatment.

Current EAU guidance states that 5-alpha-reductase inhibitors typically reduce prostate size by approximately 18–28% and lower circulating PSA by approximately 50% after sustained treatment.

Your one-year prostate reduction of approximately 16% is slightly below that typical long-term range but still entirely compatible with a meaningful treatment response.

Is a 36 cc Prostate Now “Normal”?

There is no single prostate volume that defines normal for every man because prostate size varies with age and individual anatomy.

A volume of 36 cc remains mildly enlarged by many commonly used thresholds, but the number itself is less important than:

• your current symptom severity;
• urinary flow rate;
• post-void residual;
• whether you have experienced urinary retention, infection, stones or kidney effects; and
• whether treatment is causing troublesome side effects.

Is a PVR of 40 mL Really “Urinary Retention”?

I would not describe 40 mL as significant urinary retention on its own.

Post-void residual is the amount left in the bladder after urinating. Current EAU guidance emphasizes that PVR varies between measurements and does not by itself prove prostate obstruction.

There is also no single PVR threshold that determines treatment.

Your reduction from 40 mL to 17 mL is reassuring because it suggests improved bladder emptying, but both numbers are far below the very large residual volumes commonly associated with chronic retention.

Why Did Your PSA Fall From 1.95 to 0.89?

The most likely explanation is dutasteride.

Dutasteride typically reduces PSA by about 50% within approximately 3–6 months. Your decrease of roughly 54% is therefore expected.

How Should PSA Be Interpreted While Taking Dutasteride?

This is one of the most important points missing from the original answer.

Current prescribing information recommends establishing a new PSA baseline after dutasteride has been started and monitoring PSA periodically thereafter.

For an isolated PSA value after at least several months of dutasteride treatment, clinicians commonly double the measured PSA when comparing it with reference values for men who are not taking a 5-alpha-reductase inhibitor.

Using that simple adjustment, your measured PSA of 0.89 ng/mL corresponds approximately to:

0.89 × 2 = 1.78 ng/mL

This is close to your pre-treatment PSA of 1.95 ng/mL, which is what we would expect when dutasteride is suppressing PSA normally.

What PSA Change Would Be Concerning?

Once a new low PSA baseline—sometimes called the nadir—has been established on dutasteride, any confirmed rise from that lowest value deserves assessment.

A rising PSA while consistently taking dutasteride can have several explanations, including:

• prostate inflammation or infection;
• inconsistent medication use;
• laboratory variation; or
• prostate cancer.

It does not automatically mean cancer, but it should not be ignored simply because the absolute PSA still looks “normal.”

See our PSA interpretation guide.

Will Tamdura Keep Shrinking the Prostate Until It Becomes Small?

Not indefinitely.

The greatest prostate-volume reduction generally develops during the first months to years of 5-alpha-reductase inhibitor treatment and then tends to stabilize.

EAU data show typical reductions of roughly 18–28% after sustained treatment. A man should not expect the prostate to continue shrinking every year until it becomes extremely small.

Can You Stop Tamdura Once the Prostate Has Shrunk?

This is more complicated than a simple yes or no.

Dutasteride Is Usually Long-Term Treatment

EAU guidance specifically notes that because 5-alpha-reductase inhibitors have a slow onset and reduce progression risk, they are generally suitable for long-term treatment measured in years.

If dutasteride is stopped, DHT suppression ends and prostate growth can resume over time. Therefore, reaching a smaller prostate volume does not automatically mean dutasteride is no longer useful.

The Tamsulosin Component May Sometimes Be Stopped

There is a different question regarding tamsulosin.

Combination therapy is often started because tamsulosin provides faster symptom relief while dutasteride gradually reduces the underlying prostate enlargement.

Studies have examined withdrawing the alpha blocker after approximately six to nine months of combination therapy. In one study of dutasteride plus tamsulosin, nearly three-quarters of men reported no worsening after tamsulosin was withdrawn at six months.

Men who had very severe symptoms initially were more likely to benefit from continuing both medicines longer.

This should not be attempted without your prescriber’s advice.

What Are the Main Long-Term Side Effects of Dutasteride + Tamsulosin?

The old article’s side-effect section needs some correction.

The most established adverse effects of dutasteride/tamsulosin combination treatment include:

Do Side Effects Usually Begin Only After One or Two Years?

No.

The original answer incorrectly suggested that long-term side effects usually begin after one or two years.

Clinical-trial data show that sexual side effects and dizziness can occur during the first months of treatment. In fact, some adverse effects are reported most frequently during the first year and become less frequently newly reported later.

Having taken Tamdura for one year without troublesome side effects is reassuring, but it does not guarantee that a new adverse effect can never develop.

Are Sexual Side Effects Always “Curable With Other Medicines”?

No.

If reduced libido, erectile dysfunction or ejaculation changes develop, the first step is to review:

• whether the symptom started after treatment;
• how troublesome it is;
• whether another medical condition contributes;
• whether the tamsulosin component is still needed; and
• whether changing the BPH treatment would be preferable.

Some men with erectile dysfunction may be candidates for tadalafil or another ED treatment, but it is not correct to promise that every medication-related sexual side effect can simply be “cured” by adding another drug.

What About Breast Changes?

Breast tenderness and enlargement are recognized adverse effects of dutasteride.

If you develop a breast lump, persistent one-sided enlargement, nipple discharge or other unusual breast change, do not assume it is merely a harmless medicine effect. It should be examined.

Should You Continue Another Six Months?

Your physician’s recommendation is consistent with the fact that dutasteride-based therapy is intended for long-term treatment rather than a short course.

Your current objective results are favorable:

• prostate size has decreased;
• PSA suppression is consistent with the expected dutasteride effect; and
• PVR has decreased.

However, whether you should remain on the fixed combination indefinitely depends on information not included in the question—especially your current IPSS symptom score, urine-flow rate, blood pressure, sexual side effects and personal treatment priorities.

What Should Be Monitored During Treatment?

Current EAU follow-up guidance recommends reviewing men on BPH medication using:

• symptom history and a validated symptom score such as IPSS;
• adverse effects;
• uroflowmetry when appropriate;
• post-void residual;
• PSA monitoring when clinically appropriate; and
• changes that might create an indication for surgery or further evaluation.

Once treatment is stable, follow-up can generally become less frequent rather than requiring monthly visits.