醋酸甲地孕酮
Megestrol Acetate
17-alpha-acetoxy-6-dehydro-6-methylprogesterone
別名: Ovaban · Megace · Ovarid · BDH-1298 · compound 5071 · megestroli acetas · NSC-71423 · SC-10363 · Acestrol · Borea · Endace · Gynodal · Maygace · Megastrol · Megefren · Megestat · Megestil · Megestin · Megostat · Meltonar · Meprogest · Mestrel · Niagestine · Prazoken · Varigestrol
由 VetSheet 獸醫團隊審訂更新於 2026年4月5日本內容以實證獸醫文獻為本
2.2 mg/kg once daily for 8 days starting during the first 3 days of proestrus. May be prolonged with 2.2 mg/kg/day for 4 days, then 0.55 mg/kg/day for 16-20 days.PO· q24h· 8-24 days
— 🐕
劑量為合格獸醫專業人員的臨床參考。請務必對照最新仿單及個別病患確認。
各物種劑量
🌎 NA — North America🌍 EU — Europe
狗
| 適應症 | 劑量 | 途徑 | 頻次 | 療程 | 地區 |
|---|---|---|---|---|---|
| To halt cycle in proestrus | 2.2 mg/kg once daily for 8 days starting during the first 3 days of proestrus. May be prolonged with 2.2 mg/kg/day for 4 days, then 0.55 mg/kg/day for 16-20 days. | PO | q24h | 8-24 days | 🌎 NA |
| To postpone an anticipated cycle | 0.55 mg/kg/day for 32 days, beginning at least 7 days prior to proestrus | PO | q24h | 32 days | 🌎 NA |
| To delay an anticipated heat during anestrus | 0.55 mg/kg PO for 32 days initiated 7 days prior to proestrus. | PO | q24h | 32 days | 🌎 NA |
| Estrus suppression (general) | 2 mg/kg PO once daily for 8 consecutive days | PO | q24h | 8 days | 🌎 NA |
| Temporary estrus postponement (general) | 0.5 mg/kg PO once daily in late anestrus | PO | q24h | Variable | 🌎 NA |
| Benign prostatic hypertrophy | 0.5 mg/kg PO daily for 4-8 weeks | PO | q24h | 4-8 weeks | 🌎 NA |
| Benign prostatic hypertrophy | 0.55 mg/kg PO daily | PO | q24h | Variable | 🌎 NA |
| Benign prostatic hypertrophy | 0.1-0.5 mg/kg per day for 3-8 weeks | PO | q24h | 3-8 weeks | 🌎 NA |
| Pseudocyesis (false pregnancy) | 0.5 mg/kg PO once daily for 8 days | PO | q24h | 8 days | 🌎 NA |
| To prevent vaginal hyperplasia development | 2.2 mg/kg PO for 7 days early in proestrus | PO | q24h | 7 days | 🌎 NA |
| Treatment of severe galactorrhea | 0.55 mg/kg PO once daily for 7 days | PO | q24h | 7 days | 🌎 NA |
| Adjunctive treatment of aggressive or unacceptable masculine behavior | 1.1-2.2 mg/kg PO once daily for 2 weeks, then 0.5-1.1 mg/kg once daily for 2 weeks. | PO | q24h | 4 weeks | 🌎 NA |
- To halt cycle in proestrus: Bitch must be controlled until behavioral signs of estrus disappear.
- To delay an anticipated heat during anestrus: Recommend doing vaginal cytology prior to therapy. Do not repeat therapy more often than once every 6 months.
- Benign prostatic hypertrophy: Best used to maintain breeding potential for short time prior to castration; use with caution.
- Adjunctive treatment of aggressive or unacceptable masculine behavior: Should be used with behavior modification.
貓
| 適應症 | 劑量 | 途徑 | 頻次 | 療程 | 地區 |
|---|---|---|---|---|---|
| Suppression of estrus (in anestrus) | 5 mg/cat PO every 2 weeks or 2.5 mg/cat per week (better if divided into 2 doses given every 3.5 days) | PO | q7-14d | Variable | 🌎 NA |
| Suppression of estrus (in proestrus) | 5 mg/cat per day for 4 days, then 5 mg PO every 2 weeks. | PO | q24h then q14d | Variable | 🌎 NA |
| Suppression of estrus (behavioral estrus) | 5 mg/day PO until estrus stops (generally within 3-5 days), then 2.5-5 mg PO once weekly for 10 weeks | PO | q24h then q7d | 10+ weeks | 🌎 NA |
| Postponement of estrus (started during diestrus) | 2.5 mg PO daily for 8 weeks | PO | q24h | 8 weeks | 🌎 NA |
| Postponement of estrus (started during anestrus) | 2.5 mg PO once weekly for up to 18 months. | PO | q7d | Up to 18 months | 🌎 NA |
| Prevention of estrus | 5 mg daily PO for 3 days as soon as behavioral signs of estrus are seen | PO | q24h | 3 days | 🌎 NA |
| Idiopathic feline miliary dermatitis | 2.5-5 mg once every other day, followed by weekly maintenance dosages. | PO | q48h then q7d | Variable | 🌎 NA |
| Appetite stimulant | 0.25-0.5 mg/kg q24h for 3-5 days, then q48-72h | PO | q24h then q48-72h | Variable | 🌎 NA |
| Alternative treatment for immune-mediated skin diseases | 2.5-5 mg PO once daily for 10 days, then every other day | PO | q24h then q48h | Variable | 🌎 NA |
| Adjunctive therapy of eosinophilic granulomas | 0.5 mg/kg PO once daily for 2 weeks, then twice weekly as needed | PO | q24h then twice weekly | Variable | 🌎 NA |
| Eosinophilic ulcers | 5-10 mg PO every other day for 10-14 doses, then every 2 weeks as needed | PO | q48h then q14d | Variable | 🌎 NA |
| Feline atopy ('last ditch' alternative) | 2.5-5 mg per cat PO every 48 hours for 1-3 weeks. This dose is then used once weekly. | PO | q48h then q7d | Variable | 🌎 NA |
| Feline plasma cell gingivitis | 2.5 mg PO once daily for 10 days, then once every other day for 5 treatments, then as needed | PO | q24h then q48h | Variable | 🌎 NA |
| Feline endocrine alopecia (FEA) | 5 mg PO every second to third day initially, then 2.5 mg PO once to twice weekly | PO | q48-72h then 1-2x weekly | Variable | 🌎 NA |
| Feline psychogenic alopecia and dermatitis | 2.5-5 mg every other day initially, then taper to the lowest maintenance dosage possible, given weekly as needed | PO | q48h then q7d | Variable | 🌎 NA |
| Persistent hematuria and urethritis in a non-obstructed cat | 2.5-5 mg PO once daily to every other day (with prednisone: 2.5-5 mg PO daily) | PO | q24-48h | Variable | 🌎 NA |
| Urine marking, intraspecies aggression, anxiety | 2 mg/kg/day for 5 days, then 1 mg/kg/day for 5 days, then 0.5 mg/kg/day for 5 days | PO | q24h | 15 days | 🌎 NA |
| To reduce marking in neutered male cats | 2.5-10 mg (total dose) per cat PO once daily for one week, then reduce to once or twice weekly. | PO | q24h then 1-2x weekly | Variable | 🌎 NA |
| Urine marking, intraspecies aggression, anxiety | 5 mg per cat once daily for 2 weeks, then wean to lowest effective maintenance dose. | PO | q24h | Variable | 🌎 NA |
- Postponement of estrus (started during anestrus): Recommend allowing cat to have a cycle (unmedicated) before beginning another treatment cycle.
- Prevention of estrus: Next estrus period will occur in approximately 4 weeks.
- Idiopathic feline miliary dermatitis: Reserve use for severe cases; explain risks to owner and do not exceed 2.5 mg per week during maintenance phase.
- Eosinophilic ulcers: Alone or in combination with methylprednisolone acetate.
- Feline endocrine alopecia (FEA): Secondary therapy (thyroid hormone replacement first choice).
- Persistent hematuria and urethritis in a non-obstructed cat: Adjunctive therapy.
- To reduce marking in neutered male cats: When all other drugs have been unsuccessful.
- Urine marking, intraspecies aggression, anxiety: Has poor efficacy in neutered males (50%) and spayed females (10%); many potential adverse effects.
劑量為合格獸醫專業人員的臨床參考。請務必對照最新仿單及個別病患確認。
概覽
醋酸甲地孕酮是一種強效的合成黃體素，具有顯著的抗雌激素和內在糖皮質激素特性。
在過去，它廣泛應用於獸醫學（特別是貓）以治療各種皮膚和行為問題。然而，由於其引發嚴重且有時不可逆副作用（如嚴重的腎上腺皮質抑制和醫源性糖尿病）的高風險，目前在貓的臨床使用已大幅減少。
在狗中，它仍獲 FDA 批准用於母狗的發情延遲和假孕緩解，並標示外用於公狗的良性前列腺肥大 (BPH)。在人類醫學中，它被用作食慾促進劑以及晚期乳腺癌或子宮內膜癌的姑息治療。
作用機轉
Megestrol acetate exerts its effects through multiple receptor pathways:
- Progesterone Receptors: Binds to progestin receptors → provides negative feedback to the hypothalamus and pituitary → inhibits the release of GnRH, LH, and FSH → suppresses estrus and ovulation.
- Glucocorticoid Receptors: Possesses significant intrinsic glucocorticoid activity → binds to glucocorticoid receptors → causes profound suppression of the hypothalamic-pituitary-adrenal (HPA) axis and induces insulin resistance.
- Anti-estrogenic Activity: Modifies target tissue response to estrogens.
Clinical Pearl: Unlike some other progestins, megestrol acetate does not possess significant anabolic or masculinizing effects on the developing fetus.
安全性與警告
禁忌症
- Uterine disease (e.g., pyometra, endometritis)
- Diabetes mellitus
- Mammary neoplasias
- Prior to the first estrous cycle in dogs
- Anestrus therapy in dogs with abnormal cycles
- During diestrus or in the presence of uterine hemorrhage
- Treatment of pseudopregnancy in bitches (per manufacturer, though off-label protocols exist)
不良反應
- Profound adrenocortical suppression (especially in cats)
- Transient or permanent diabetes mellitus
- Cystic endometrial hyperplasia (CEH) and pyometra
- Mammary hypertrophy and neoplasia
- Increased appetite and weight gain
- Polydipsia and polyuria (PU/PD)
- Lethargy and personality changes
- Hepatotoxicity (rare)
- Acromegaly (dogs)
- Lactation (rare)
注意事項
Black Box Warning Equivalent: Megestrol acetate can induce profound, life-threatening adrenocortical suppression and iatrogenic Addisonian crisis, particularly in cats.
- Adrenal Suppression: Because of its glucocorticoid activity, patients may require exogenous stress-dose steroids during periods of trauma, surgery, or severe illness.
- Reproductive Risks: High risk of inducing cystic endometrial hyperplasia (CEH) and pyometra. A thorough reproductive history, physical exam, mammary palpation, and vaginal cytology are strongly recommended before initiating therapy for reproductive control.
- Infection Risk: May exacerbate latent viral infections (e.g., Feline Herpesvirus-1).
- Human Safety: Pregnant women should handle this medication with extreme caution (FDA Category X in early pregnancy).
藥物交互作用
Corticosteroids
Concurrent long-term use may exacerbate adrenocortical suppression and increase the risk of diabetes mellitus.
Rifampin
May decrease progestin activity due to microsomal enzyme induction, resulting in increased progestin metabolism.
監測
- Body weight
- Blood glucose (draw baseline before therapy)
- Mammary gland development and appearance (nodules/hypertrophy)
- Adrenocortical function (ACTH stimulation test if indicated)
- Liver enzymes (especially with long-term treatment)
- Clinical efficacy
藥物動力學
半衰期
狗8 days
吸收
Well absorbed from the gastrointestinal tract.
分佈
Widely distributed. Detectable amounts of progestins enter the milk of nursing mothers.
代謝
Appears to be metabolized completely in the liver to conjugates and free steroids.
排除
Excreted primarily via urine and feces.
過量
Acute toxicity from overdosage has not been reported. In humans, massive doses (up to 800 mg/day) caused no observable acute adverse reactions.
Chronic Toxicity in Dogs:
- Dosages of 0.1-0.25 mg/kg/day PO for 36 months yielded no gross abnormalities, but histologically, cystic endometrial hyperplasia (CEH) was noted (resolved when therapy was discontinued).
- Dosages of 0.5 mg/kg/day PO for 5 months caused reversible uterine hyperplasia.
- Dosages of 2 mg/kg/day demonstrated early cystic endometritis within 64 days.
可用產品
劑型
- Oral tablets
- Oral suspension
獸醫用
- Megestrol Acetate Oral Tablets: 5 mg, 20 mg (Ovaban)
人用標示
- Megestrol Acetate Tablets: 20 mg, 40 mg (Megace)
- Megestrol Acetate Suspension: 40 mg/mL, 125 mg/mL (Megace, Megace ES)
各地核准狀態
暫無法規資料: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
儲存與穩定性
Store tablets in well-closed containers at a temperature of less than 40°C. The veterinary manufacturer recommends storing the tablets from 2°-30°C (36°-86°F). Tablets may be crushed and administered with food.
飼主須知
醋酸甲地孕酮是一種強效的荷爾蒙藥物。雖然它可能有效，但伴隨著顯著的風險，特別是在貓身上。
- 了解風險：此藥物可能引起嚴重的副作用，包括糖尿病、嚴重的子宮感染（子宮蓄膿）以及腎上腺抑制。
- 密切監測：密切觀察寵物的飲水量和排尿量。如果牠們開始過度飲水或排尿，請立即聯繫獸醫，因為這可能是糖尿病的徵兆。
- 身體變化：定期檢查寵物的乳腺（腹部區域）是否有腫脹、腫塊或分泌物。如有任何變化請向獸醫報告。
- 行為與活力：注意是否有極度嗜睡、虛弱或行為上的突然改變。
- 請勿突然停藥：如果您的寵物長期服用此藥，請勿在未諮詢獸醫的情況下突然停藥，因為牠們的身體需要時間適應。
- 人類安全：孕婦應避免接觸此藥物。
VetSheet 藥物參考供合格獸醫專業人員作臨床決策輔助之用，不能取代專業判斷或廠商最新仿單。