메트로니다졸
메트로니다졸은 수의학에서 널리 사용되는 합성 니트로이미다졸계 항균 및 항원충제입니다. **주요 임상 적용:** * **항원충:** 지알디아(Giardia), 트리코모나스(Trichomonas), 이질아메바(Entamoeba histolytica), 대장섬모충(Balantidium coli)에 매우 효과적입니다. * **항혐기성균:** 절대 혐기성균(예: 박테로이데스, 클로스트리디움, 푸소박테리움)에 대해 우수한 효능을 보입니다. 패혈증, 복막염, 깊은 교상 등을 포함한 장내 및 전신 혐기성 감염 치료에 자주 사용됩니다. * **위장관 조절:** 염증성 장질환(IBD) 및 만성 대장염 관리에 자주 활용됩니다. **임상 팁:** 항균 특성 외에도 메트로니다졸은 세포 매개 면역을 억제함으로써 위장관에서 국소적인 면역 조절 및 항염증 효과를 갖는 것으로 여겨집니다. **중요 고려사항:** * **FDA에 의해 식용 동물에 대한 사용이 엄격히 금지되어 있습니다**. * 매우 쓴 금속성 맛으로 악명이 높으며, 특히 고양이에서 심한 침흘림과 투약 거부를 유발할 수 있습니다. 고양이 환자의 경우 타액에 덜 녹아 쓴맛이 덜한 조제용 메트로니다졸 벤조에이트가 종종 선호됩니다.
작용 기전: Metronidazole is a concentration-dependent bactericidal agent. **Mechanism Pathway:** 1. **Entry:** The drug enters the cell of the organism via passive diffusion. 2. **Activation:** In obligate anaerobes and certain protozoa, the nitro group of metronidazole is reduced by electron-transport proteins (such as **ferredoxin**). 3. **DNA Disruption:** This reduction process creates highly reactive, short-lived cytotoxic intermediate compounds (free radicals) → These radicals bind to and disrupt **DNA and nucleic acid synthesis** → leading to rapid cell death. Because aerobic bacteria lack the specific electron-transport proteins required to reduce and activate the drug, metronidazole is virtually inactive against obligate aerobes.
동물 종별 용량
- Giardia · 15-25 mg/kg · PO · q12-24h · 5-7 days
- Giardia · 25 mg/kg · PO · q12h · 7 days
- Giardia · 22 mg/kg · PO · twice daily · 5 days · May be combined with fenbendazole
- Entamoeba histolytica or Pentatrichomas hominis · 25 mg/kg · PO · q12h · 8 days
- H. pylori · 10-15 mg/kg · PO · two times a day · 14 days · With clarithromycin 7.5 mg/kg PO BID and amoxicillin 20 mg/kg PO BID
- Sepsis · 15 mg/kg · IV · q12h
- Inflammatory bowel disease (mild to moderate large bowel) · 10-20 mg/kg · PO · two to three times a day
- Inflammatory bowel disease · 62.5 mg (total dose) · PO · once daily · 10-20 days · With a change of diet to 'hypoallergenic'
- Inflammatory bowel disease (moderate to severe) · 10-15 mg/kg · PO · q8-12h · Combine with prednisone
- Hepatic encephalopathy · 7.5 mg/kg · PO · q8-12h
- Helicobacter mustelae gastritis infections · 22 mg/kg · PO · 3 times daily · 3-4 weeks · Using triple therapy with amoxicillin 22 mg/kg and bismuth subsalicylate 17.6 mg/kg
투여 경로
금기
- Hypersensitivity to metronidazole or other nitroimidazole derivatives
- Food-producing animals (FDA prohibited)
- Pregnancy (potential teratogen, especially in early pregnancy)
- Severe hepatic disease (requires dose reduction)
이상반응
- Neurologic disorders (ataxia, nystagmus, seizures, head-tilt)
- Lethargy and weakness
- Neutropenia
- Hepatotoxicity
- Hematuria
- Anorexia, nausea, vomiting, and diarrhea
- Hypersalivation (especially in cats due to bitter taste)
- Vomiting
- CNS toxicity (nystagmus, ataxia, knuckling, head tilt, seizures)
- Haematuria
- Excessive salivation/foaming (especially in cats)
- Impaired sense of smell (reported in explosive detection dogs)
약물 상호작용
- Alcohol · May induce a disulfiram-like reaction (nausea, vomiting, cramps).
- Cimetidine · May decrease the metabolism of metronidazole, increasing the likelihood of dose-related side effects. · major
- Phenobarbital · May increase the metabolism of metronidazole, thereby decreasing blood levels. · moderate
- Phenytoin · May increase the metabolism of metronidazole, thereby decreasing blood levels. · moderate
- Warfarin · May prolong the prothrombin time (PT). Avoid concurrent use or intensify monitoring.
- Macrolide antibiotics · Should not be used concurrently with Spiramycin (in combination products) as the combination may be antagonistic. · moderate
모니터링
- Clinical efficacy (resolution of diarrhea, negative fecal tests)
- Adverse effects (especially neurologic signs like ataxia or nystagmus)
- Neurological signs (for early detection of CNS toxicity)
- Liver function tests (ALT, AST, Bilirubin) in patients with pre-existing hepatic disease
- Complete Blood Count (for neutropenia)
과용량
Signs of intoxication in dogs and cats are primarily neurologic and include: * Anorexia and/or vomiting * Depression * Mydriasis (dilated pupils) * **Nystagmus** (rapid eye flicking, very common in dogs) * **Ataxia** (stumbling, uncoordinated gait) * Head-tilt, proprioceptive deficits, joint knuckling * Tremors, seizures, rigidity, and stiffness These effects may be seen with acute massive overdoses, or more commonly with chronic therapy at doses >60 mg/kg/day (though sometimes seen at 'recommended' doses like 30 mg/kg/day). **Treatment:** * Discontinue metronidazole immediately. Most dogs with mild to moderate signs improve rapidly within 1-2 days of stopping the drug. * **Diazepam** has been used successfully to rapidly decrease the CNS effects associated with metronidazole toxicity. * For acute massive ingestions, standard decontamination protocols (emesis, activated charcoal) apply, but use **extreme caution** before inducing vomiting if the patient is already showing CNS signs, due to aspiration risk.
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