5α還元酵素阻害薬（前立腺を小さくする薬）

代表的な薬

• フィナステリド(日本では不採用）
• デュタステリド

作用

• 男性ホルモンの作用を抑制
• 前立腺そのものを縮小

特徴

• 効果発現まで時間がかかる（3〜6か月）
• 前立腺体積が大きい人ほど有効

向いている方

• 前立腺が大きい（30–40mL以上）
• 将来の尿閉や手術リスクを下げたい方

注意点

• 性欲低下
• 勃起機能低下
• PSA値が約半分になる（解釈に注意）

文責　加藤忍　（院長、日本泌尿器科学会専門医、藤田医科大学泌尿器科客員教授）

5α-Reductase Inhibitors

(Medications That Shrink the Prostate)

Common Medications

• Finasteride (not commonly used in Japan)

• Dutasteride

How These Medications Work

• Reduce the effect of male hormones (androgens)

• Gradually shrink the prostate itself

Key Characteristics

• Effects take time to appear (usually 3–6 months)

• More effective in men with a larger prostate

Who May Benefit Most

• Men with an enlarged prostate (30–40 mL or larger)

• Those who wish to reduce the future risk of acute urinary retention or surgery

Important Points to Know

• Possible decrease in sexual desire

• Possible erectile dysfunction

• PSA levels are reduced by about 50%, so PSA results must be interpreted carefully

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Author:
Shinobu Kato, MD, PhD
Director
Board-Certified Urologist, Japanese Urological Association
Visiting Professor, Department of Urology, Fujita Health University