乙胺嘧啶
Pyrimethamine
Aminopyrimidine derivative
別名: Daraprim · Malocide · Pirimecidan · BW-50-63 · pirimetamina · pyrimethaminum · RP-4753
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
劑量為持牌獸醫專業人員的臨床參考。請務必對照最新藥品說明書及個別病患確認。
各物種劑量
🌎 NA — North America🌍 EU — Europe
狗
| 適應症 | 劑量 | 途徑 | 頻次 | 療程 | 地區 |
|---|---|---|---|---|---|
| Toxoplasmosis | 0.5-1 mg/kg PO once daily for 2 days, then 0.25 mg/kg PO once daily for 2 weeks | PO | once daily | 2 days, then 2 weeks | 🌎 NA |
| Toxoplasmosis | 0.25-0.5 mg/kg once daily for 28 days | PO | once daily | 28 days | 🌎 NA |
| Neospora | 1 mg/kg once daily for 28 days | PO | once daily | 28 days | 🌎 NA |
| Hepatazoon canis | 0.25-0.5 mg/kg once daily for 2-4 weeks | PO | once daily | 2-4 weeks | 🌎 NA |
| Hepatazoon americanum | 0.25 mg/kg PO q24h | PO | q24h | — | 🌎 NA |
| Hepatazoon americanum | 0.25 mg/kg PO q24h for 14 days | PO | q24h | 14 days | 🌎 NA |
| Neosporosis | 1 mg/kg PO daily | PO | daily | — | 🌎 NA |
- Toxoplasmosis: Given with sulfadiazine at 30-50 mg/kg PO divided two to four times a day for 1-2 weeks
- Neospora: Given with trimethoprim sulfa
- Hepatazoon canis: Given with trimethoprim sulfa and clindamycin
- Hepatazoon americanum: Given with Trimethoprim/sulfa (15 mg/kg PO q12h) and clindamycin (10 mg/kg q8h). Once remission attained, decoquinate can maintain.
- Hepatazoon americanum: Given with Trimethoprim/sulfa (15 mg/kg PO q12h for 14 days) and clindamycin (10 mg/kg q8h for 14 days). Once remission attained, decoquinate can maintain.
- Neosporosis: Given with trimethoprim/sulfa (15-30 mg/kg PO twice daily).
貓
| 適應症 | 劑量 | 途徑 | 頻次 | 療程 | 地區 |
|---|---|---|---|---|---|
| Toxoplasmosis | 0.5-1 mg/kg PO once daily for 2 days, then 0.25 mg/kg PO once daily for 2 weeks | PO | once daily | 2 days, then 2 weeks | 🌎 NA |
| Toxoplasmosis (enteroepithelial cycle) | 2 mg/kg, PO once daily | PO | once daily | — | 🌎 NA |
| Toxoplasmosis (extraintestinal cycle) | 0.5-1 mg/kg PO divided two to three times daily | PO | divided two to three times daily | — | 🌎 NA |
| Protozoal myocarditis | 1 mg/kg PO once daily for 3 days, then decrease dose to 0.5 mg/kg PO once a day | PO | once daily | 3 days, then ongoing | 🌎 NA |
| Toxoplasmosis | 0.5 mg/kg PO per day | PO | per day | 7-10 days | 🌎 NA |
- Toxoplasmosis: Given with sulfadiazine at 30-50 mg/kg PO divided two to four times a day for 1-2 weeks
- Toxoplasmosis (extraintestinal cycle): Combined with sulfonamides (e.g., triple sulfa, sulfadiazine) at 60 mg/kg PO or IM divided two to three times daily
- Protozoal myocarditis: Given with sulfadimethoxine 25 mg/kg PO, IV, or IM once a day
- Toxoplasmosis: Given with sulfadiazine at 30 mg/kg, PO q12h. Do not use continuously for longer than 2 weeks. Supplementation with folic acid 5 mg/day or folinic acid 1 mg/kg/day may alleviate toxicity.
鳥
| 適應症 | 劑量 | 途徑 | 頻次 | 療程 | 地區 |
|---|---|---|---|---|---|
| Coccidian organisms in raptors (Toxoplasmosis, Atoxoplasmosis, Sarcocystis) | 0.5 mg/kg PO twice daily for 14-28 days | PO | twice daily | 14-28 days | 🌎 NA |
馬
| 適應症 | 劑量 | 途徑 | 頻次 | 療程 | 地區 |
|---|---|---|---|---|---|
| Equine protozoal myeloencephalitis | 1 mg/kg PO once a day for 90-120 days (or longer) | PO | once a day | 90-120 days (or longer) | 🌎 NA |
- Equine protozoal myeloencephalitis: Given with a sulfa or potentiated sulfa (sulfadiazine 20 mg/kg PO once or twice a day). Monitor CBC's.
劑量為持牌獸醫專業人員的臨床參考。請務必對照最新藥品說明書及個別病患確認。
概覽
乙胺嘧啶是一種強效的抗原蟲藥，在獸醫學中主要用於治療小動物嚴重的原蟲感染，如弓形蟲症 (toxoplasmosis)、新孢子蟲症 (neosporosis) 和 Hepatozoon americanum，以及馬的馬原蟲性脊髓腦炎 (EPM)。它幾乎總是與磺胺類藥物合併使用，以達到協同阻斷葉酸合成的效果。
臨床要點： 由於其標靶為葉酸代謝，宿主骨髓抑制是一個顯著的風險，特別是在貓。通常建議補充亞葉酸 (folinic acid，而非葉酸，因為原蟲有時能利用葉酸) 或烘焙酵母來減輕血液學毒性。
作用機制
Pyrimethamine is a folic acid antagonist. It competitively inhibits the enzyme dihydrofolate reductase (DHFR) → blocks the reduction of dihydrofolic acid to tetrahydrofolic acid (the active form of folate) → depletes folate reserves essential for purine and pyrimidine synthesis → halts protozoal DNA and RNA synthesis.
When combined with sulfonamides (which inhibit dihydropteroate synthase earlier in the pathway), it produces a synergistic, sequential blockade of the folate synthesis pathway.
安全性與警告
禁忌症
- Known hypersensitivity to pyrimethamine
- Preexisting hematologic disorders (use with extreme caution)
- Pregnancy (potentially teratogenic, weigh risks vs. benefits)
- Pregnancy (teratogenic)
- Pre-existing bone marrow suppression
不良反應
- Small animals: Anorexia, malaise, vomiting, depression
- Small animals: Bone marrow depression (anemia, thrombocytopenia, leukopenia)
- Cats: Highly susceptible to adverse reactions (noted 4-6 days after starting combination therapy)
- Horses: Leukopenias, thrombocytopenia, and anemias
- Bone marrow suppression (anemia, leukopenia, thrombocytopenia)
- Lethargy
注意事項
Hematologic Toxicity: Hematologic effects can develop rapidly. Frequent monitoring is recommended, particularly if therapy persists longer than 2 weeks. Oral administration of folinic acid, folic acid, or Brewer's yeast has been suggested to alleviate adverse effects.
Feline Sensitivity: Some clinicians recommend avoiding its use in cats entirely because of its adverse effect profile.
Pregnancy: Pyrimethamine is teratogenic in rats and fetal abnormalities have been seen in foals. FDA Category C. Weigh risks against benefits. Excreted in maternal milk; consider using milk replacer.
藥物相互作用
Reportedly antagonistic towards the activity of pyrimethamine; clinical significance is unclear.
Synergistic with pyrimethamine in activity against toxoplasmosis and malaria.
Use with pyrimethamine/sulfa is not recommended in humans as adverse effects may be additive, however, this combination has been used clinically in horses.
May increase folate deficiency
May increase folate deficiency
監測
- CBC with platelet count (frequent monitoring recommended)
- Clinical efficacy
- Signs of abnormal bleeding or lassitude
- Complete Blood Count (CBC) every 1-2 weeks
- Appetite and body weight
- Signs of bleeding, bruising, or lethargy
藥物動力學
半衰期
吸收
No pharmacokinetic data located for veterinary species. In humans, well absorbed from the gut after oral administration.
分佈
Distributed primarily to the kidneys, liver, spleen, and lungs. Crosses the blood-brain barrier. Volume of distribution is about 3 L/kg. 80% bound to plasma proteins. Enters milk in levels greater than serum.
代謝
Unknown how or where the drug is metabolized, but metabolites are found in the urine.
排除
Excreted in the urine.
過量
Reports of acute overdosage in animals were not located. In humans, signs include vomiting, nausea, anorexia, CNS stimulation (including seizures), and hematologic effects.
Treatment recommendations:
- Standard procedures to empty the gut or prevent absorption.
- Parenteral barbiturates for seizures.
- Folinic acid for hematologic effects.
- Long-term monitoring (at least 1 month) of renal and hematopoietic systems.
可用產品
劑型
- Tablets: 25 mg
- 25 mg tablet
人用標示
- Pyrimethamine Tablets: 25 mg; Daraprim® (GlaxoSmithKline); (Rx)
- Daraprim 25 mg tablets
各地核准狀態
Often used under the cascade from human medicine.
Listed as a Pharmacy (P) medicine in the provided monograph.
暫無法規資料: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
儲存與穩定性
Store tablets in tight, light-resistant containers. Tablets may be crushed to make oral suspensions. If cherry syrup, corn syrup, or sucrose-containing liquids are used, store the suspension at room temperature and discard after 7 days (sugars adversely affect stability).
飼主須知
重要提示： 此藥物用於治療嚴重的寄生蟲感染，需要仔細監測。
- 嚴格按照指示給藥： 通常與其他抗生素（如磺胺類藥物）一起給予，以達到最大療效。請勿漏服。
- 注意副作用： 如果您的寵物變得嗜睡、食慾不振、嘔吐，或出現異常出血或瘀傷的跡象（如牙齦蒼白或皮膚紅斑），請立即聯繫您的獸醫。
- 貓咪給藥挑戰： 市售錠劑為 25 毫克，這使得貓咪的準確劑量非常困難。此外，錠劑對貓來說味道很差。您的獸醫可能會建議使用特製的懸浮液或膠囊，以確保劑量準確且易於餵食。
- 懷孕警告： 如果您懷孕了，請勿接觸此藥物；除非獸醫明確指示，否則請勿用於懷孕的寵物。
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