피리메타민 및 설파디아진

항원충제 / 엽산 길항제

**피리메타민 및 설파디아진(Pyrimethamine and sulfadiazine)**은 시너지 효과를 내는 항균 및 항원충 복합제로, 수의학에서는 주로 *Sarcocystis neurona*에 의해 유발되는 **말 원충성 척수뇌염(EPM)** 치료에 사용됩니다. * **시너지 작용:** 설파계 약물과 디아미노피리미딘계 약물을 결합하여 엽산 합성 경로를 연속적으로 차단함으로써 감수성이 있는 원충과 세균에 치명적인 효과를 나타냅니다. * **허가 외 사용(Off-label Uses):** FDA에서는 말에게만 승인되었으나, 소동물 임상에서는 고양이의 **톡소플라스마증(Toxoplasmosis)**이나 개의 **네오스포라증(Neosporosis)**과 같은 중증 원충 감염 치료를 위해 허가 외로 사용되기도 합니다. * **임상적 주의사항:** EPM 치료에는 장기간(보통 3~9개월)의 투약이 필요합니다. 전신적인 엽산 결핍으로 인한 골수 억제 위험이 있으므로 수의사의 세심한 모니터링이 필수적입니다.

작용 기전: This combination exerts its antiprotozoal and antibacterial effects through a **sequential blockade** of the folic acid synthesis pathway, which is essential for nucleic acid (DNA/RNA) production in the parasite: 1. **Sulfadiazine** acts as a structural analogue of para-aminobenzoic acid (**PABA**). It competitively inhibits the enzyme **dihydropteroate synthase**, blocking the conversion of PABA → **dihydrofolic acid (DFA)**. 2. **Pyrimethamine** specifically targets and inhibits the enzyme **dihydrofolate reductase**, blocking the conversion of DFA → **tetrahydrofolic acid (THFA)** (the active form of folate). > **Pharmacological Pearl:** Pyrimethamine has a much higher affinity for protozoal dihydrofolate reductase compared to bacterial or mammalian forms, making it highly effective against protozoal parasites like *Sarcocystis neurona* and *Toxoplasma gondii*.

동물 종별 용량

Horses

Treatment of EPM · 20 mg/kg sulfadiazine with 1 mg/kg pyrimethamine; equivalent to 4 mL of ReBalance suspension per 50 kg (110 lb) body weight · PO · once daily · 90-270 days (based upon clinical response) · Administer at least 1 hour before feeding with hay or grain. Administer using a suitable oral dosing syringe; insert nozzle through the interdental space and deposit the dose on the back of the tongue.
Maintaining clinical remission (for horses that have had two relapses) · pyrimethamine/sulfadiazine · PO · twice weekly (first and fourth day of each week) · Ongoing · After completing regular therapy for EPM.

용량은 면허 수의 전문가를 위한 임상 참고 자료입니다. 항상 최신 라벨과 개별 환자에 대해 확인하십시오.

투여 경로

금기

Hypersensitivity to pyrimethamine or sulfadiazine
Horses intended for human consumption

이상반응

Bone marrow suppression (anemia, leukopenia, neutropenia, thrombocytopenia)
Reduced appetite or anorexia
Loose stools or diarrhea
Urticaria (hives)
Treatment crisis (temporary worsening of neurologic signs due to parasite die-off)
CNS effects (seizures, depression - though often secondary to the underlying EPM)

약물 상호작용

Antacids · May decrease the bioavailability of sulfonamides if administered concurrently.
Highly protein-bound drugs (e.g., methotrexate, phenylbutazone, thiazide diuretics, salicylates, probenecid, phenytoin, warfarin) · Sulfonamides may displace other highly bound drugs, potentially increasing their free (active) plasma concentrations and risk of toxicity.
p-Aminobenzoic acid (PABA) · Reportedly antagonistic towards the activity of pyrimethamine; clinical significance is unclear.
Trimethoprim · Use with pyrimethamine/sulfa is not recommended in humans as adverse effects may be additive; however, this combination has been used clinically in horses.

모니터링

CBC (including platelets): baseline and at least monthly during therapy
GI adverse effects (appetite, stool consistency)
Clinical Efficacy: Improvement in neurologic signs
CSF Western Blot test (monitoring for negative status)

과용량

Acute overdosage information (>2X) in horses is not well documented. When administered at **2X the labeled dose for 92 days**, signs included loose stools, slight increases in ALP, declines in red blood cell parameters (RBC, HCT, Hgb, PCV), and depressed appetite. Treatment should be supportive and symptomatic.

VetSheet 약물 레퍼런스는 면허 수의 전문가를 위한 임상 의사결정 보조 도구이며, 전문적 판단이나 제조사의 최신 라벨을 대신하지 않습니다.