エストラジオールシピオネート
エストラジオールシピオネートは、長時間作用型の天然エストロゲンエステル誘導体です。歴史的には小動物の妊娠中絶薬（交尾後の避妊）として広く使用されてきましたが、**致命的な骨髄抑制**（再生不良性貧血）や**子宮蓄膿症**を引き起こすリスクが高いため、現在ではほとんどの獣医繁殖専門医によって推奨されていません。より安全で効果的な代替薬が好まれています。 > **臨床上の注意点**：FDAは、この薬物を食用動物に使用することを厳格に禁止しており、対象動物への投与や調剤は違法となります。
作用機序: Estradiol is the most active endogenous estrogen. It diffuses across the cell membrane and binds to specific intracellular **estrogen receptors (ERα and ERβ)**. The receptor-hormone complex translocates to the nucleus → binds to **estrogen response elements (EREs)** on DNA → modulates gene transcription. **Key systemic effects include:** * **Reproductive:** Stimulates normal growth and development of female sex organs, increases cervical mucosal secretions, thickens vaginal mucosa, and induces endometrial proliferation and uterine tone. * **Skeletal:** Increases calcium deposition, accelerates epiphyseal closure, and promotes bone formation. * **Endocrine:** Modulates pituitary gonadotropin release, which can inhibit lactation, ovulation, and androgen secretion.
動物種別の用量
- Pregnancy avoidance after mismating · 250 micrograms/kg (0.25 mg/kg) IM once 6 days after coitus; or 0.25 mg/cat IM at 40 hours after coitus · IM · once · Rarely used for this indication today as there are safer, more effective treatments.
- Any · Illegal · The FDA has stated that the use of ECP in food-producing animals is illegal.
- To enhance estrus behavior and receptivity in ovariectomized mares · 5-10 mg (total dose) IM once · IM · once
- Treatment of mares with estrogen-responsive incontinence · 4-10 micrograms/kg estradiol cypionate IM daily for three days and then every other day · IM · daily then q48h · 3 days then ongoing · Some mares will improve, but does not 'cure'.
- Pregnancy avoidance after mismating · 44 micrograms/kg (0.044 mg/kg) IM once; during day 4 estrus to day 2 of diestrus · IM · once · Rarely used for this indication today as there are safer, more effective treatments. Toxic at >=100 micrograms/kg.
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- Pregnancy (teratogenic and causes fetal bone marrow depression)
- Food-producing animals (illegal per FDA)
- Ferrets (highly susceptible to severe bone marrow toxicity)
- Estrogen-responsive incontinence in small animals (safer alternatives like DES or estriol should be used)
有害事象
- Bone marrow toxicity (thrombocytopenia, leukopenia, fatal aplastic anemia)
- Cystic endometrial hyperplasia
- Pyometra
- Mammary neoplasia
- Feminization (in males)
- Prolonged estrus (in females)
- Genital irritation (cattle)
- Decreased milk flow (cattle)
- Follicular cysts (cattle)
薬物相互作用
- Azole Antifungals (fluconazole, itraconazole, ketoconazole) · May increase estrogen levels due to CYP450 enzyme inhibition.
- Corticosteroids · Enhanced glucocorticoid effects; estrogens may alter protein binding or decrease metabolism of corticosteroids.
- Macrolide Antibiotics (erythromycin, clarithromycin) · May increase estrogen levels.
- Phenobarbital · May decrease estrogen activity via hepatic enzyme induction.
- Rifampin · May decrease estrogen activity via hepatic enzyme induction.
- St. John's Wort · May decrease estrogen activity.
- Warfarin · Oral anticoagulant activity may be decreased; dosage adjustments may be necessary.
モニタリング
- Packed Cell Volumes (PCV)
- White blood cell counts (CBC)
- Platelet counts (Baseline, one month after therapy, and repeated two months after cessation if abnormal)
- Liver function tests
過量投与
Acute overdosage reports in veterinary patients are rare, but chronic or high-dose exposure leads to severe adverse effects. **Overdose manifestations:** * **Small Animals:** Severe bone marrow depression (thrombocytopenia, leukopenia, aplastic anemia), cystic endometrial hyperplasia, and pyometra. * **Cattle:** Prolonged estrus, genital irritation, decreased milk flow, precocious development, and follicular cysts. Treatment is largely supportive. If bone marrow suppression occurs, aggressive supportive care (transfusions, broad-spectrum antibiotics) is required, though prognosis for aplastic anemia is poor.
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。