テストステロン
**テストステロン (Testosterone)** は主要な内因性のアンドロゲン（雄性ホルモン）であり、獣医療では主に特定のホルモンおよび生殖関連の用途に限って注射用エステル製剤が使用されます。 - **小動物**: 主に去勢雄犬および猫の**ホルモン反応性尿失禁**の治療に使用されます。まれに去勢雄犬の特定の左右対称性脱毛（皮膚炎）の治療にも使用されます。 - **大動物**: 牛の臨床では、発情発見用の「あて牛（ティーザー）」を作成するために使用されます。 - **臨床上の注意点**: 家畜の性欲減退や不妊症の治療に対する効果は一般的に期待外れです。 - **規制**: テストステロン製剤はアナボリックステロイドに分類されるため、**規制薬物（C-III）**に指定されています。
作用機序: Testosterone is highly lipophilic and diffuses across target cell membranes. In many tissues, it is converted by **5-alpha-reductase** → **dihydrotestosterone (DHT)**. Both testosterone and DHT bind to intracellular **androgen receptors** → the receptor complex translocates to the nucleus → binds to DNA hormone response elements → modulates gene transcription. - **Urethral Tone**: Helps maintain normal urethral muscle tone and mucosal integrity in neutered males. - **Anabolic Effects**: Increases protein anabolism and decreases catabolism → retention of nitrogen, sodium, potassium, and phosphorus. - **Erythropoiesis**: Stimulates **erythropoietic stimulating factor (erythropoietin)** → increases red blood cell production. - **Endocrine Feedback**: Large exogenous doses exert negative feedback on the pituitary gland → inhibits **luteinizing hormone (LH)** and **follicle-stimulating hormone (FSH)** → inhibits spermatogenesis.
動物種別の用量
- Infertility or reduced libido · 0.1-1 mg every other day or every third day for 3-5 injections IM or SC. Not indicated for testis descent. · IM/SC · every other day or every third day · 3-5 injections · Using either testosterone cypionate or propionate
- Testosterone-responsive urinary incontinence (may be used with phenylpropanolamine) in males · Testosterone propionate 5-10 mg IM as needed. · IM · as needed
- To produce an estrus-detector (teaser) animal (cull cows, heifers, steers) · Testosterone propionate 200 mg IM on day 1 and on days 4-9. On day 10, give 1 gram IM and attach a chinball marker and put with the breeding herd. To maintain the teaser give 1 gram booster every 10-14 days. · IM · varies
- To produce an estrus-detector (teaser) animal (cull cows, heifers, steers) · Alternatively, initially give testosterone enanthate 0.5 gram IM and 1.5 gram SC (divided in two separate locations). After 4 days attach chinball marker and put in with breeding herd. To maintain, give 0.5-0.75 gram SC every 10-14 days. · IM/SC · varies
- Testosterone-responsive urinary incontinence (may be used with phenylpropanolamine) in males · Testosterone propionate: approximately 2 mg/kg IM or SC 3 times per week. Testosterone cypionate: 200 mg IM once per month · IM/SC · 3 times per week / once per month
- Testosterone-responsive urinary incontinence · Testosterone propionate: 2.2 mg/kg IM q2-3 days. Testosterone cypionate: 2.2 mg/kg IM once per month · IM · q2-3 days / once per month
投与経路
禁忌
- Known hypersensitivity to the drug
- Prostate carcinoma
- Pregnancy (FDA Category X / Papich Class D)
有害事象
- Perianal adenomas
- Perineal hernias
- Prostatic disorders (enlargement)
- Behavior changes (aggression)
- Polycythemia (at high doses)
- Oligospermia or infertility (in intact males with chronic use)
薬物相互作用
- Corticosteroids · May enhance the edema associated with ACTH or adrenal steroid therapy
- Insulin / Oral Antidiabetic Agents · Testosterone may decrease serum glucose levels
- Propranolol · Testosterone cypionate may increase propranolol clearance
- Warfarin · Testosterone may increase anticoagulant effects
モニタリング
- Clinical efficacy (resolution of incontinence, estrus detection behavior)
- Adverse effects (prostatic enlargement, aggression, perineal hernias)
- Hematocrit/PCV (for polycythemia with chronic use)
過量投与
No specific acute toxicity information is available. - **Chronic Overdose**: High dosages or chronic usage may result in oligospermia or infertility in intact males due to negative feedback on LH/FSH. - **Other Effects**: Polycythemia (excessive red blood cells) has been reported in humans receiving high dosages. - **Treatment**: Discontinue therapy and provide supportive care. Monitor hematocrit and prostatic size.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。