Quick Answer
Finasteride and dutasteride both shrink an enlarged prostate and reduce the long-term risk of acute urinary retention and BPH surgery. Dutasteride blocks both type 1 and type 2 5-alpha-reductase and suppresses circulating DHT more strongly than finasteride, which mainly blocks type 2.
However, stronger DHT suppression does not clearly mean greater prostate shrinkage in real patients. EAU 2026 states that direct and indirect comparative evidence finds the two medicines broadly equally effective for LUTS, while randomized-trial meta-analyses have found no significant difference in prostate-volume reduction.
Both are slow treatments intended for men with a demonstrably enlarged prostate and meaningful progression risk. They commonly reduce prostate volume by roughly 18–28% over long-term treatment and lower PSA by approximately 50%. Choosing between them depends more on prostate size, clinical history, drug persistence, cost/formulary, side effects and clinician preference than on an expectation that one will dramatically shrink the gland more.
What Are Finasteride and Dutasteride?
Finasteride and dutasteride belong to a medication class called 5-alpha-reductase inhibitors (5-ARIs).
For BPH, the usual prescription doses are:
- finasteride 5 mg once daily;
- dutasteride 0.5 mg once daily.
Unlike alpha blockers such as tamsulosin, which relax smooth muscle and can improve symptoms relatively quickly, 5-ARIs change the hormonal environment that supports prostate growth. Their effect develops gradually over months.
They are particularly useful when urinary symptoms occur together with a demonstrably enlarged prostate and a meaningful risk that BPH will progress.
For the complete medication overview, see BPH Medications: Alpha Blockers, 5-ARIs, Tadalafil & More.
How Do Finasteride and Dutasteride Work?
Testosterone is converted to dihydrotestosterone (DHT) by the enzyme 5-alpha-reductase. DHT is a major androgen signal involved in prostate growth.
There are two clinically relevant isoenzymes:
- type 1 — more prominent in tissues such as skin and liver;
- type 2 — particularly important in reproductive tissues including the prostate.
Finasteride
Finasteride mainly inhibits type 2 5-alpha-reductase.
EAU reports that continuous treatment reduces circulating DHT by approximately 70%.
Dutasteride
Dutasteride inhibits both type 1 and type 2 5-alpha-reductase.
That broader blockade reduces circulating DHT by approximately 95%.
Why Doesn’t 95% vs 70% Automatically Mean More Prostate Shrinkage?
Because serum DHT is not the same as DHT inside prostate tissue.
EAU notes that despite the much larger difference in circulating DHT, both drugs reduce intraprostatic DHT to a similar range of approximately 85–90%.
This helps explain why the clinical difference between them is smaller than the blood-DHT numbers might suggest.
Finasteride vs Dutasteride: Which Shrinks the Prostate More?
Current evidence does not establish a major, reliable prostate-shrinkage advantage for dutasteride over finasteride.
EAU 2026 groups both medicines together and reports that after two to four years of treatment, 5-ARIs generally reduce prostate volume by approximately 18–28%.
A randomized-trial meta-analysis comparing the two drugs found:
- no significant difference in prostate-volume reduction;
- no significant difference in post-void residual;
- no clear difference in adverse reactions;
- some small differences favoring dutasteride in selected symptom/PSA outcomes.
Another meta-analysis of eight randomized trials similarly found only a very small advantage in maximum urinary flow for dutasteride, not proof of dramatically greater gland shrinkage.
Do Not Choose Dutasteride Only Because “It Blocks More DHT”
Dual enzyme inhibition is pharmacologically real, but treatment choice should be based on clinical outcomes rather than assuming that a 95% fall in serum DHT must produce a proportionally greater reduction in prostate size.
Do Finasteride and Dutasteride Improve BPH Symptoms Differently?
Overall, their clinical effect is similar.
EAU states that one direct comparative trial and indirect evidence indicate that dutasteride and finasteride are equally effective for LUTS.
Across the 5-ARI class, after two to four years treatment typically:
- improves IPSS by approximately 15–30%;
- reduces prostate volume by approximately 18–28%;
- and improves Qmax by about 1.5–2.0 mL/s.
These are averages across study populations, not promises for an individual patient.
Do They Prevent BPH From Getting Worse?
This is one of the most important reasons to use a 5-ARI.
Unlike alpha blockers, finasteride and dutasteride can reduce the long-term risk of:
- acute urinary retention;
- and BPH-related surgery.
Finasteride demonstrated major reductions in those risks in long-term PLESS and MTOPS trials. Dutasteride has likewise demonstrated reduction in retention and BPH surgery risk.
This is why 5-ARIs are considered disease-modifying BPH medications, not merely symptom-relief drugs.
Which Prostate Sizes Benefit Most?
5-ARIs work best when the prostate is genuinely enlarged.
EAU gives prostate volume above approximately 40 mL as a practical example of increased progression risk for which a 5-ARI should be considered in men with moderate-to-severe LUTS.
AUA guidance has commonly used evidence of enlargement such as:
- prostate volume above roughly 30 cc;
- PSA above approximately 1.5 ng/mL as a surrogate for enlargement;
- or palpable enlargement on examination.
A Nuance Between 30 and 40 mL
EAU notes that finasteride may not clearly outperform placebo in men whose prostates are below about 40 mL.
Dutasteride has evidence showing benefit in some men with prostate volumes between 30 and 40 mL.
This is one area where dutasteride can be a reasonable consideration, but it does not mean every 35 mL prostate should receive dutasteride.
Symptoms, progression risk and anatomy still matter.
If you need help understanding the scan number first, see Normal Prostate Size by Age: What Do 30, 40, 50 and 80 cc Mean?.
Finasteride vs Dutasteride: What Happens to PSA?
Both lower PSA substantially.
EAU reports an approximate 50% reduction after six to twelve months of 5-ARI therapy.
Drug labels likewise warn that finasteride and dutasteride can reduce PSA by about half.
Why This Matters
A lower PSA after starting a 5-ARI does not mean prostate-cancer risk has disappeared. Your clinician establishes a new PSA baseline after treatment begins.
Any confirmed rise from the new PSA baseline deserves evaluation, even when the absolute PSA number still looks “normal” for a man not taking a 5-ARI.
PSA is prostate-specific but not cancer-specific. BPH itself can raise PSA, and 5-ARI treatment changes how the result must be interpreted.
Read PSA Test: Levels, Results, Screening & What Happens Next.
Which Works Faster: Finasteride or Dutasteride?
Neither should be considered a fast BPH medicine.
5-ARIs require months to produce their full clinical effect because prostate tissue gradually changes in response to reduced DHT signaling.
EAU states that clinical effects relative to placebo generally become evident after at least about six months.
Why Dutasteride Stays in the Body Much Longer
The drugs differ dramatically in pharmacokinetics:
- finasteride half-life: approximately 6–8 hours;
- dutasteride half-life: approximately 5 weeks.
This does not mean dutasteride takes five weeks to start working. It means the drug is eliminated much more slowly and can remain detectable for months after treatment stops.
That prolonged persistence is clinically important for pregnancy-exposure and blood-donation precautions.
Side Effects: Is Finasteride Safer Than Dutasteride?
The adverse-effect profiles are broadly similar because both suppress DHT.
EAU identifies the main urological adverse effects as:
- reduced libido;
- erectile dysfunction;
- reduced semen volume;
- and other ejaculatory dysfunction.
Breast tenderness or enlargement occurs in a small minority; EAU estimates approximately 1–2%.
Randomized-trial meta-analyses comparing finasteride with dutasteride have not shown a clear overall difference in adverse reactions.
For a more detailed finasteride-specific safety discussion, see Finasteride Side Effects: Sexual, Mood, Fertility, PSA & Safety.
Do Sexual Side Effects Always Continue?
No. Some patients do not experience sexual adverse effects at all, and some effects improve during treatment or after discontinuation.
Persistent symptoms have also been reported and should be discussed with a clinician rather than dismissed.
Mood Changes and Suicidal Thoughts: Current 2026 Safety Information
This section needs to reflect the important European safety update from 2025.
EMA’s EU-wide review confirmed suicidal thoughts as a side effect of finasteride tablets, including both 1 mg and 5 mg formulations. The frequency could not be estimated from available data.
Most reported cases involved the 1 mg hair-loss dose, but the safety finding applies to oral finasteride tablets.
For dutasteride, EMA found insufficient evidence to establish a direct causal association with suicidal thoughts. However, because dutasteride acts through the same drug class, its product information includes a precautionary warning about mood changes and suicidal ideation.
Seek Medical Advice for New Mood Symptoms
If you develop depressed mood, depression or suicidal thoughts while taking finasteride or dutasteride, contact a healthcare professional promptly. Do not ignore new mental-health symptoms simply because the medicine was prescribed for a benign urinary condition.
Fertility, Pregnancy Exposure and Blood Donation
Finasteride
Pregnant women or women who may be pregnant should not handle crushed or broken finasteride tablets because systemic absorption could pose a risk to development of a male fetus.
Intact 5 mg tablets are coated, which prevents contact with the active ingredient during normal handling.
Dutasteride
Dutasteride can be absorbed through skin. Pregnant women or women who may be pregnant should not handle leaking dutasteride capsules.
If skin contact with leaking contents occurs, the area should be washed promptly with soap and water.
Dutasteride and Blood Donation
Because dutasteride persists for a long time, the U.S. prescribing information states that men should not donate blood while taking dutasteride or for at least six months after the final dose.
Dutasteride and Semen Parameters
Official prescribing information reports that dutasteride can reduce:
- total sperm count;
- semen volume;
- and sperm motility
in some men. The clinical significance for an individual man’s fertility remains uncertain.
If fertility is currently important, discuss it before starting long-term therapy.
Can Finasteride or Dutasteride Cause Prostate Cancer?
Neither drug should be described as “causing prostate cancer” in a simple sense.
Older prevention trials found a higher proportion of high-grade cancers among men assigned to 5-ARIs, and product labels retain warnings about a possible increased risk of high-grade prostate cancer.
However, interpretation is complicated by:
- prostate shrinkage improving cancer detection;
- changes in biopsy sampling;
- PSA suppression;
- and trial design.
EAU states that a causal relationship has not been proven.
The practical message is to use these drugs for an appropriate BPH indication and interpret PSA correctly—not to use them as prostate-cancer prevention supplements.
Finasteride or Dutasteride With an Alpha Blocker
For men with moderate-to-severe symptoms plus an enlarged prostate and progression risk, a 5-ARI is often combined with an alpha blocker.
The logic is straightforward:
- the alpha blocker provides relatively rapid symptom relief;
- the 5-ARI works slowly to reduce prostate volume and future progression risk.
Long-term MTOPS and CombAT data show that combination therapy provides stronger overall protection against progression than alpha-blocker monotherapy.
The tradeoff is more adverse effects because the patient is exposed to both drug classes.
EAU therefore recommends combination treatment primarily for men with moderate-to-severe LUTS and increased progression risk—for example, a prostate volume above about 40 mL.
Finasteride vs Dutasteride: Which Should You Choose?
Finasteride May Be a Good Fit If:
- you have a clearly enlarged prostate and need a 5-ARI;
- cost or formulary favors finasteride;
- your clinician has a strong reason to use the established type-2 inhibitor;
- you prefer a medication that leaves the body much more quickly after stopping;
- there is no reason to favor dual enzyme inhibition.
Dutasteride May Be a Good Fit If:
- dual type 1 + type 2 inhibition is preferred;
- your prostate is clearly enlarged;
- your prostate volume is around 30–40 mL and your clinician considers the dutasteride-specific evidence useful;
- the drug is covered and well tolerated;
- long persistence after stopping is not a disadvantage.
What Should Not Decide the Choice?
I would not choose dutasteride solely because its serum DHT suppression is “95% instead of 70%.”
I would also not choose finasteride solely because it has been available longer.
The clinically relevant questions are:
- Is the prostate actually enlarged enough for a 5-ARI to help?
- How bothersome are the symptoms?
- What is the long-term progression risk?
- What is the PSA baseline?
- Are sexual side effects particularly important?
- Is fertility a current concern?
- What other medications and medical conditions are present?
- Which drug is available and affordable?
If poor bladder emptying is part of the problem, see Post-Void Residual (PVR): How Much Urine Left in the Bladder Is Too Much?
Dr. Albana’s Note
Patients often assume dutasteride must be much stronger because it blocks two forms of 5-alpha-reductase and lowers circulating DHT more profoundly. Pharmacologically, that is true. Clinically, the difference is less dramatic.
Inside prostate tissue, both drugs suppress DHT strongly, and comparative trials have not shown a clear difference in prostate-volume reduction. So I would not promise a patient that dutasteride will shrink his prostate substantially more than finasteride.
I would instead ask whether he is a good candidate for a 5-ARI at all. These drugs are most useful when the gland is demonstrably enlarged and long-term progression prevention matters. They are not fast symptom-relief drugs, and a man with a small prostate and severe urinary symptoms may have a different problem.
I would also explain the PSA issue before treatment. When PSA falls by about half, future results have to be interpreted against the new baseline. A later confirmed rise deserves assessment rather than reassurance based on the absolute number alone.
Finally, side effects matter. Sexual symptoms, fertility concerns and mood changes should be discussed openly. The correct medication is the one that fits the patient’s anatomy, risk profile and priorities—not simply the one that produces the larger laboratory reduction in DHT.
— Dr. Albana Greca, MD, MMedSc, Family Physician / General Practitioner
Frequently Asked Questions About Finasteride vs Dutasteride
Does dutasteride shrink the prostate more than finasteride?
Not clearly. Dutasteride suppresses circulating DHT more strongly, but randomized-trial meta-analyses have not shown a significant, consistent difference in prostate-volume reduction.
How much can finasteride shrink the prostate?
Across 5-ARI studies, prostate volume generally falls by roughly 18–28% over long-term treatment. The individual response depends strongly on starting prostate size and duration of treatment.
How much can dutasteride shrink the prostate?
Dutasteride falls within the same overall 5-ARI range of approximately 18–28% prostate-volume reduction over long-term treatment. Some individual studies report different figures, but comparative evidence does not establish a large consistent advantage over finasteride.
Which lowers DHT more?
Dutasteride lowers circulating DHT more strongly—about 95% versus about 70% with finasteride. Within prostate tissue, however, both suppress DHT to a much more similar degree.
Which lowers PSA more?
Both typically lower PSA by approximately 50%. Some comparative studies have found small differences, but both require a new PSA baseline and careful interpretation of subsequent rises.
Which works faster?
Neither is fast. Both usually require several months for meaningful clinical benefit. An alpha blocker may be added when faster symptom relief is needed.
Which has more sexual side effects?
Both can cause reduced libido, erectile dysfunction and ejaculatory changes. Comparative randomized evidence has not established a clear overall difference in adverse-event rates.
Which stays in the body longer?
Dutasteride by far. Its half-life is approximately five weeks, compared with about six to eight hours for finasteride.
Can I switch from finasteride to dutasteride?
Sometimes, but the reason for switching should be discussed with your prescriber. Because both act slowly and dutasteride persists for months, treatment changes should be planned rather than made based on a few days of symptoms.
Can finasteride or dutasteride prevent BPH surgery?
They reduce the long-term risk of acute urinary retention and the need for BPH surgery in appropriately selected men with enlarged prostates, but they cannot guarantee that surgery will never be needed.
Related BPH Medication Guides
Medical References
- European Association of Urology. Guidelines on the Management of Non-neurogenic Male Lower Urinary Tract Symptoms: Disease Management. 2026. Finasteride inhibits type 2 5-alpha-reductase; dutasteride inhibits types 1 and 2. Both reduce prostate volume approximately 18–28%, PSA approximately 50%, and reduce BPH progression risk.
- Goueli R, et al. Management of Lower Urinary Tract Symptoms Attributed to Benign Prostatic Hyperplasia: AUA Guideline (2026) Part II: Medical Management. J Urol. 2026;216(2):152-160. PMID 42095477.
- The efficacy and safety of dutasteride and finasteride in patients with benign prostatic hyperplasia: a systematic review and meta-analysis. Eight randomized controlled trials, 2,116 patients. PMID 35402192.
- Zhou Z, et al. Efficacy and safety of dutasteride compared with finasteride in treating males with benign prostatic hyperplasia: A meta-analysis of randomized controlled trials. PMID 32742388.
- European Medicines Agency. Finasteride- and dutasteride-containing medicinal products: measures to minimise risk of suicidal thoughts. 2025.
- DailyMed prescribing information for finasteride 5 mg and dutasteride 0.5 mg: PSA effects, pregnancy exposure, semen characteristics and blood-donation precautions.
Medical information notice: Finasteride and dutasteride are prescription medicines. The decision to start, stop or switch a 5-alpha-reductase inhibitor should be based on prostate size, symptoms, PSA, progression risk, side effects, fertility considerations, other medications and clinician assessment.
Written & medically reviewed by Dr. Albana Greca, MD, MMedSc • Family Physician / General Practitioner • Founder & Lead Medical Author • Last medically reviewed: September 2026