BPH用薬：この2つの薬の働きと費用

最終更新日: 2026年8月27日

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Benign prostatic enlargement becomes commoner with every decade — affecting roughly four men in ten in their fifties, more than seven in ten in their sixties, and the large majority by their eighties. It is not dangerous in itself, and it is not something every man needs treating: plenty of men have an enlarged prostate and symptoms mild enough to live with comfortably.

For those who do want treatment, two classes of tablet are used, and they do entirely different things. For the condition itself see 前立腺の肥大 — the link on this page previously pointed to an address that no longer exists.

• タイ・バンコク病院 泌尿器科センター オンライン予約 02-310-3009 bhquro@bdms.co.th
• サミティベート・シラチャ病院(チョンブリ) 088-022-1445

Alpha-blockers: fast, and they do not shrink anything

These relax the smooth muscle of the prostate and bladder neck, widening the channel. They work within days, and are the usual first choice.

They do not change the prostate or slow the condition — stop the tablet and the symptoms return. That is not a criticism; for many men it is exactly what is wanted.

What they do to you

• Dizziness and light-headedness on standing, since they lower blood pressure. Worst in the first days and in older men, which is why the first dose is usually taken at night.
• Reduced or absent ejaculation. The earlier version mentioned abnormal ejaculation in passing without saying what that means. It means the volume falls, sometimes to nothing at all. It is harmless, it reverses on stopping, and men who are not warned about it often stop the tablet believing something has gone badly wrong. It is commoner with some drugs in the class than others, so it is worth raising rather than enduring — switching frequently solves it.
• They do not cause erectile dysfunction — worth stating plainly, since men frequently assume otherwise and blame the tablet.
• Added to a PDE5 inhibitor for erections, blood pressure can drop more than either drug would cause alone. Tell whoever prescribes either that you take the other.

Tell your eye surgeon — even years later

This was absent from the earlier version and is the single most useful practical point about the class.

Alpha-blockers change the behaviour of the iris during cataract surgery, and the effect persists long after the tablet has been stopped. Forewarned, the surgeon adjusts the technique and the operation proceeds normally; taken by surprise mid-operation, it is a genuine problem. Anyone who has ever taken one should mention it before any eye operation, however long ago it was.

5-alpha reductase inhibitors: slow, and only if the prostate is large

These block the conversion of testosterone to dihydrotestosterone, the androgen that drives prostatic growth. Over about six months the prostate shrinks by up to roughly a third, and — unlike the alpha-blockers — they genuinely change the course of the condition, reducing the risk of ending up in retention or needing an operation.

One qualification matters more than anything else here and was not stated in the earlier version: they only work if the prostate is actually enlarged. In a man with a small prostate and troublesome symptoms, adding one produces the side effects without the benefit. Prostate size, measured or estimated, is what decides whether this drug belongs in the plan — not symptom severity.

The PSA point every man on one of these needs

The earlier version gave the fact — these drugs halve the PSA — without the instruction that goes with it.

After about six months on treatment, double your PSA result to interpret it. A reading of 2 in a man on one of these drugs behaves like a 4 in a man who is not. And tell whoever orders the test that you take it — a man on finasteride or dutasteride with a PSA that looks comfortably normal may not be comfortably normal at all, and this is one of the recognised routes to a delayed prostate cancer diagnosis.

What matters even more than the doubling is the direction: a PSA that rises while on one of these drugs is abnormal and needs investigating, whatever the absolute number looks like. See what a raised PSA means.

What they do to you

• Reduced sex drive, erectile difficulty, and reduced ejaculate volume, in a minority. These usually settle or reverse on stopping.
• 乳房の痛みや大きさが増す, uncommon.
• Persistent sexual symptoms and low mood have been reported in some men after stopping, and are the subject of ongoing debate rather than settled fact. The honest position is that it is uncertain, uncommon, and worth knowing about before starting a drug that is taken for years — particularly by a younger man taking it for hair loss rather than for a prostate.
• Women who are or may become pregnant must not handle broken or crushed tablets, because of the effect on a male fetus. Intact tablets are coated for this reason.

Using both together

The two are complementary: one gives relief within days but changes nothing underlying, the other changes the course but takes half a year. Combined, they outperform either alone in men with a genuinely enlarged prostate and more than mild symptoms — and that qualification is the whole point. The earlier version described combination therapy as preferred for moderate-to-severe symptoms generally, which is too broad: in a man whose prostate is not large, it means two sets of side effects for the benefit of one drug.

Two further honest points. It is treatment taken indefinitely — stopping returns things to baseline. And some men, told they face two tablets a day for the rest of their lives, would rather have a one-off procedure instead. That is a legitimate preference and worth raising rather than assuming tablets are the default.

It is also worth knowing that a poor stream is not always the prostate. A 尿道狭窄症 produces identical symptoms, and a bladder that has become underactive will not improve with prostate medication at all — which is what フローテスト helps to sort out.

Symptoms that need attention rather than a repeat prescription

タイで緊急の場合は、次の番号に電話してください 1669.

• 排尿の完全な不可能な状態 with a painful full bladder — same-day treatment.
• Fever with pain low down or on passing urine.
• 尿中に血が見える, which needs investigating rather than attributing to the prostate.
• A PSA that is rising while on a 5-alpha reductase inhibitor.
• New bone pain or unexplained weight loss.
• Symptoms that came on over weeks rather than years, or in a man under about fifty.

Frequently Asked Questions About BPH Medication

How quickly does each drug work?

An alpha-blocker improves the stream within days. A 5-alpha reductase inhibitor takes around six months to shrink the prostate meaningfully, and its benefit in reducing retention and surgery builds over years of continued use.

I take finasteride or dutasteride. What about my PSA?

After about six months these drugs roughly halve the PSA, so double the result to interpret it and tell whoever orders the test that you take one. More important than the number is the trend — a PSA rising while on one of these drugs is abnormal and needs investigating regardless of how normal it looks.

Should everyone with BPH be on both drugs?

No. Combination therapy outperforms either drug alone in men with a genuinely enlarged prostate and more than mild symptoms. Where the prostate is not large, adding a 5-alpha reductase inhibitor gives the side effects without the benefit. Prostate size decides, not symptom severity.

My ejaculate has disappeared since starting the tablet. Is that serious?

No — it is a recognised effect of alpha-blockers, harmless, and reverses on stopping. It is commoner with some drugs in the class than others, so raise it rather than enduring it or stopping treatment on your own; switching often resolves it.

Do alpha-blockers cause erectile dysfunction?

No, and this is often assumed. They affect ejaculation, not erections. 5-alpha reductase inhibitors can affect desire and erections in a minority. If you take a tablet for erections as well, be aware that combining it with an alpha-blocker can lower blood pressure more than either alone.

Do I have to take these forever?

They work only while taken, and stopping returns symptoms to baseline. Some men prefer a one-off procedure to indefinite medication, which is a reasonable preference and worth discussing rather than assuming tablets are the default.

診察のご予約について

Dr. Soarawee Weerasopone の診察場所は次のとおりです Bangkok Hospital Headquarters また、チョンブリー県の Samitivej Sriracha Hospital でも次の曜日に診察を行っています 088-022-1445. Bring every previous PSA result with its date and a list of your medicines — including anything taken for hair loss, which is the same drug class and affects the PSA identically.

来院が難しい海外の患者さんを含め、バンコク病院の遠隔診療をご利用いただけます。事前に泌尿器科へ次のメールアドレスまでご連絡のうえ、ご予約ください: bhquro@bdms.co.th。サミティベート・シラチャー病院は対面診療のみです。費用に関するお問い合わせには病院が対応しており、本ウェブサイトでは対応しておりません。

免責事項: 本コンテンツは、Bangkok Hospital Headquarters に勤務する泌尿器科専門医(認定医)の Dr. Soarawee Weerasopone が執筆・監修したもので、教育目的のみを意図しています。個々の方に対する医学的助言、診断、処方ではなく、個人メッセージやソーシャルメディアを通じて助言、診断、処方を行うことはありません。Dr. Soarawee は公開のソーシャルメディアアカウントを運営しておらず、彼の名前で個別相談を提供するアカウントは詐欺です。タイで緊急の場合は、次の番号に電話してください 1669.