アルトレノゲスト
アルトレノゲスト（Altrenogest）は、獣医繁殖医学で広く使用されている合成経口プロゲスチンです。 - **馬**：牝馬の発情を抑制して周期を同期させたり、黄体機能不全や胎盤炎の牝馬の妊娠を維持するために使用されます。 - **豚**：性成熟した未経産豚の発情同期化に使用されます。 - **犬**：黄体機能不全や早産防止のための子宮収縮抑制剤として適応外使用されます。 > **臨床上の注意**：本剤は脂溶性が高く、無傷の皮膚から容易に吸収されます。取扱者（特に妊婦や血栓塞栓症、エストロゲン依存性疾患の既往歴がある人）にとって重大な健康リスクを伴います。
作用機序: Altrenogest acts as an agonist at **progesterone receptors**. - Transforms proliferative endometrium into secretory endometrium. - Enhances myometrial hypertrophy and inhibits spontaneous uterine contractions (tocolytic effect). - Exerts negative feedback on the hypothalamus and pituitary gland → inhibits secretion of **GnRH** → decreases release of pituitary gonadotropins (**FSH** and **LH**), thereby suppressing estrus and ovulation in a dose-dependent manner.
動物種別の用量
- To suppress estrus for synchronization · 1 mL per 110 pounds body weight (0.044 mg/kg) · PO · once daily · 15 consecutive days · May administer directly on tongue using a dose syringe or on the usual grain ration.
- For prevention of abortion/pregnancy loss · 0.088 mg/kg · PO · once daily
- To maintain pregnancy in mares with deficient progesterone levels · 0.044 mg/kg · PO · once daily · Until day 60, 120, or end of pregnancy · Three options: 1) until day 60+ AND endogenous progesterone >4 ng/mL; 2) until day 120; 3) until end of pregnancy.
- To maintain pregnancy in mares with placentitis · 22-44 mg (total dose; 10-20 mL) · PO · daily
- To suppress estrus (long-term) · 0.044 mg/kg · PO · daily
- For synchronization of estrous in sexually mature gilts that have had at least one estrous cycle · 6.8 mL (15 mg) per gilt · PO · once daily · 14 consecutive days · Apply as a top-dressing on a portion of gilt's daily feed allowance. Estrous should occur 4-9 days after completing treatment.
- Luteal insufficiency · 2 mL per 100 lbs of body weight · PO · once daily · Document luteal insufficiency and rule out infectious causes. Best to avoid during first trimester. Monitor pregnancy with ultrasound. Monitor carefully for pyometra.
- Luteal insufficiency, pre-term labor · 0.1 mL per 10 lb body weight · PO · once daily
- To maintain pregnancy if tocolytics (e.g., terbutaline) do not control myometrial contractility · 0.088 mg/kg · PO · q24h · Must be withdrawn 2-3 days prior to predicted whelp date.
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
- Horses intended for food purposes
- Mares with chronic uterine infections
- Manufacturer lists pregnancy as a contraindication (though clinically used extensively to maintain pregnancy)
有害事象
- Minimal at labeled dosages
- Slight, sporadic elevations in Ca++, K+, alkaline phosphatase, and AST
- May exacerbate chronic uterine infections
- Risk of pyometra in dogs (due to exogenous progesterone effects)
薬物相互作用
- Rifampin · May decrease progestin activity if administered concomitantly due to microsomal enzyme induction and increased progestin metabolism.
モニタリング
- Pregnancy viability (via ultrasound)
- Endogenous progesterone levels (if treating luteal deficiency)
- Signs of pyometra in dogs
過量投与
The LD50 of altrenogest is 175-177 mg/kg in rats. No specific information is available regarding the effects of an accidental acute overdose in horses or other veterinary species.
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。