Prostate · Medication Guide
Finasteride 5 mg for BPH in Thailand
What finasteride 5 mg does for an enlarged prostate, how well it works, its side effects, and how men in Bangkok get it legally. This is the 5 mg prostate dose, not the 1 mg hair-loss tablet. Reviewed by a licensed physician at a MOPH-registered men's health clinic.
- Full effect in 6–12 months
- Thai FDA registered · prescription only
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Medically reviewed by Dr. Noppon Arunkajohnsak (Win)
Menscape Clinic
Last reviewed
11 July 2026
57%
Lower risk of retention
acute urinary retention, over four years
~20%
Smaller prostate volume
typical shrinkage over 6–12 months
6–12
Months to full effect
on flow, symptoms and prostate size
50%
Lower PSA reading
tell any doctor who screens your prostate
Key takeaways
Finasteride 5 mg is an oral prescription medicine that shrinks an enlarged prostate by lowering DHT. It is a different dose and purpose from the 1 mg hair-loss tablet.
Over four years, it cut the risk of acute urinary retention by 57% and the need for BPH surgery by 55% in a 3,040-man trial.
In Thailand it is a dangerous drug (ยาอันตราย): pharmacist- or doctor-dispensed only, never over the counter, and unlicensed online sellers are illegal and unsafe.
It works slowly and only while you take it, and it roughly halves PSA, so a doctor must confirm it fits your prostate and any prostate screening must account for it.
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What finasteride 5 mg is & how it shrinks the prostate
Finasteride 5 mg is an oral prescription medicine used to treat benign prostatic hyperplasia (BPH), the non-cancerous enlargement of the prostate that gradually squeezes the urethra and causes a weak stream, hesitancy, dribbling, and waking at night to urinate. It is common: the prostate slowly enlarges in most men from middle age onward.
It works upstream of the growth. The prostate is driven to enlarge by dihydrotestosterone (DHT), a stronger by-product of testosterone. Finasteride blocks 5α-reductase, the enzyme that makes DHT, lowering it by roughly 70%. With less DHT, the gland stops being told to grow and slowly shrinks, by about a fifth over 6 to 12 months, which widens the channel and improves flow.
This is the same molecule as the 1 mg hair-loss tablet, at five times the dose and for a different problem. It treats the enlargement itself rather than just relaxing muscle, so it works slowly but addresses the underlying cause. Whether it suits you depends on how large your prostate is, your symptoms and your PSA, which is what the doctor's assessment is for.
Testosterone → DHT
The enzyme 5α-reductase converts testosterone into DHT, the hormone that drives prostate growth.
DHT enlarges the prostate
In BPH, DHT makes the gland grow and press on the urethra, weakening and interrupting urine flow.
Finasteride blocks the enzyme
One daily 5 mg tablet lowers DHT by about 70%, removing the growth signal.¹
The prostate shrinks
Over 6–12 months the gland shrinks by roughly a fifth, easing flow, urgency and night-time trips.²
02
Getting finasteride 5 mg in Thailand
Thai FDA status
Registered with the Thai FDA and classified as a dangerous drug (ยาอันตราย). The 5 mg prostate strength, sold in Thailand under brands such as Proscar and several registered generics, is a separate product from the 1 mg hair tablet, and comes only through licensed channels.⁴
Where it's legal to get
From a licensed pharmacy (first-class pharmacist) or on prescription from a doctor at a licensed clinic. Teleconsultation with licensed telepharmacy delivery is also legal in Thailand.⁵
For expats & visitors
No Thai residency is required. Bring your history and any recent PSA result; a doctor can review continuity if you already take a 5α-reductase inhibitor abroad.
Thai FDA warning. The regulator repeatedly warns against buying prescription medicines from unlicensed online sellers. Counterfeit prostate medicines circulate, and nobody is accountable for what you actually receive.⁷
03
Does it work? The evidence
Finasteride 5 mg is one of the most-studied BPH treatments. In the pivotal four-year randomised trial of 3,040 men with moderate-to-severe symptoms (PLESS), it reduced the risk of acute urinary retention by 57% and the need for BPH-related surgery by 55% compared with placebo, while shrinking prostate volume by roughly 18%.²
Two things to know before you start. It is slow: symptom and flow improvements build over 6 to 12 months, not days, and it works best when the prostate is genuinely enlarged. Longer-term research found the benefit is durable while treatment continues, and that pairing it with an alpha-blocker prevents disease progression better than either alone.³ The effect lasts only while you take it, because the prostate slowly regrows once DHT returns.
57%
Lower retention risk
acute urinary retention over four years, vs placebo
55%
Lower surgery risk
need for BPH-related surgery, same trial
PLESS: 3,040 men with moderate-to-severe BPH, four-year randomised placebo-controlled trial. Individual results vary.
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Side effects & who shouldn't take it
Common sexual side effects
Decreased libido, erectile difficulty and ejaculation problems (including reduced ejaculate volume) are the most reported effects, each in the low single-digit percentages in trials. They often ease over time and, in most men, resolve after stopping.¹
Less common, worth knowing
Breast tenderness or enlargement (gynaecomastia) can occur; any new breast lump, pain or nipple discharge should be checked promptly. Mood changes have also been reported, so tell your doctor about any history of depression.¹
Not suitable for
Women, and children. Pregnant women must not handle crushed or broken tablets, because finasteride can harm a developing male fetus. It is also avoided in anyone hypersensitive to it, and used with care in significant liver disease.
PSA & prostate screening
Finasteride roughly halves PSA, the blood marker used to screen for prostate cancer. Tell any doctor who tests your PSA that you take it, so your result can be doubled and read correctly. Otherwise a rising level can be masked.¹
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Alternatives & combinations
Oral · faster symptom relief
Doxazosin & alfuzosin
Alpha-blockers relax the muscle in the prostate and bladder neck, easing flow within days rather than months. A doctor often combines one with finasteride, which slows progression better than either drug alone.
Oral · treats BPH + ED
Tadalafil
A low daily dose of this PDE5 inhibitor is licensed for BPH symptoms and is useful when an enlarged prostate and erectile difficulty occur together, letting one medicine address both.
Oral · stronger DHT block
Dutasteride
A related 5α-reductase inhibitor that blocks both forms of the enzyme and lowers DHT further. A doctor may consider it for a larger prostate or when the finasteride response is insufficient.
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How prescription works at Menscape
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Book your prostate consultation today.
Message us on WhatsApp or LINE
A few minutes on your phone: your urinary symptoms, health history, current medications and any recent PSA. It is PDPA-protected.
Doctor consultation
A licensed Thai physician reviews your case by video or in clinic at Asoke, and may arrange a PSA test or flow check before deciding on treatment.
Prescription, if suitable
If the doctor judges finasteride appropriate, you receive a prescription dispensed by a licensed pharmacy, for pickup or delivery.
Follow-up & monitoring
Symptom scores and PSA are rechecked over the following months, and your plan is adjusted with your doctor as the prostate responds.
The doctor decides. Starting a conversation is not a commitment and does not guarantee a prescription. If finasteride is not right for you, your doctor will say so and discuss alternatives.
Medically reviewed by
Dr. Noppon Arunkajohnsak (Win)
Menscape Clinic, Bangkok
“An enlarged prostate is common and very manageable, but finasteride is slow and it is not right for every man. The first step is measuring your prostate, your symptoms and your PSA, not reaching for a tablet.”
- Reviewed
- 11 July 2026
- Next review
- January 2027
- Editorial standard
- Each guide is checked against the Thai FDA label and the primary literature, then reviewed by a licensed physician.
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Frequently asked questions
Can I buy finasteride 5 mg over the counter in Thailand?
No. It is classified as a dangerous drug (ยาอันตราย), so it must be dispensed by a licensed pharmacist or prescribed by a doctor. Anything sold without that oversight is illegal and carries a real counterfeit risk.
Is finasteride 5 mg the same as the 1 mg hair-loss tablet?
It is the same molecule at five times the dose, for a different purpose. The 5 mg tablet is used to shrink an enlarged prostate, while the 1 mg tablet is used for male-pattern hair loss. Do not swap between them on your own; a doctor sets the right dose for your condition.
How long before my urine flow improves?
Finasteride works slowly. Most men notice a gradual improvement in flow and night-time trips over 6 to 12 months, not days. If you need faster relief, a doctor may add an alpha-blocker, which acts within days.
Will it affect my sex drive or erections?
It can. Lower libido, erectile difficulty and ejaculation changes are the most common side effects, each in the low single-digit percentages in trials. They often ease over time and usually resolve if you stop; tell your doctor if they bother you.
Can finasteride cause breast enlargement?
Breast tenderness or enlargement (gynaecomastia) is an uncommon but recognised effect. Any new breast lump, pain or nipple discharge should be reported to your doctor promptly so it can be examined.
I'm due for a PSA or prostate-cancer check. Does finasteride affect it?
Yes. Finasteride roughly halves your PSA reading. Always tell the doctor doing the test that you take it, so they can double the value and interpret it correctly, rather than being falsely reassured by a low number.
Can I take it with my blood-pressure or erectile-dysfunction medication?
Usually, yes. Finasteride is often combined with an alpha-blocker for BPH and can be taken alongside PDE5 inhibitors such as tadalafil under medical guidance. Give your doctor a full list of your medicines so interactions and blood pressure are managed safely.
Do I have to take it forever?
The benefit lasts only while you take it. If you stop, DHT rises again and the prostate slowly regrows over the following months, so symptoms tend to return. Your doctor will review whether continuing makes sense for you.
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References
1. U.S. FDA. Proscar® (finasteride 5 mg) prescribing information. Merck & Co. Accessed July 2026.
2. McConnell JD, et al. The effect of finasteride on the risk of acute urinary retention and the need for surgical treatment among men with benign prostatic hyperplasia (PLESS). N Engl J Med. 1998;338(9):557-563.
3. McConnell JD, et al. The long-term effect of doxazosin, finasteride, and combination therapy on the clinical progression of BPH (MTOPS). N Engl J Med. 2003;349(25):2387-2398.
4. Thai Food and Drug Administration. Drug registration database (ndi.fda.moph.go.th). Accessed July 2026.
5. Pharmacy Council of Thailand, Notification No. 56/2563 on telepharmacy standards.
6. American Urological Association. Management of Benign Prostatic Hyperplasia (BPH) guideline. 2021 (amended 2023).
7. Thai FDA consumer warnings on purchasing medicines from unlicensed online sellers, oryor.com.
This guide is educational information, not medical advice. Finasteride 5 mg is a prescription medicine that must be prescribed and monitored by a licensed physician. Urinary symptoms should always be assessed by a doctor to rule out other causes, including prostate cancer.
This guide is part of the Menscape prostate library
Explore the condition hubWeak stream or waking up to pee? Ask a urologist, not a forum.
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