甲硝唑 / 滅滴靈
甲硝唑是一種合成的硝基咪唑類抗菌及抗原蟲藥物，在獸醫學中被廣泛使用。 **主要臨床應用：** * **抗原蟲：** 對梨形鞭毛蟲 (Giardia)、滴蟲 (Trichomonas)、溶組織內阿米巴 (Entamoeba histolytica) 和結腸小袋纖毛蟲 (Balantidium coli) 具有高度療效。 * **抗厭氧菌：** 對絕對厭氧菌（如擬桿菌屬、梭狀芽孢桿菌屬、梭桿菌屬）具有極佳的抗菌效果。常被用於治療腸道及全身性厭氧菌感染，包括敗血症、腹膜炎和深層咬傷。 * **胃腸道調節：** 經常被用於控制炎症性腸病 (IBD) 和慢性結腸炎。**臨床要點：** 除了抗菌特性外，甲硝唑被認為在胃腸道中具有局部免疫調節和抗發炎作用，特別是透過抑制細胞介導的免疫反應。 **重要注意事項：** * **FDA 嚴格禁止用於產食動物**。 * 以其極度苦澀的金屬味而聞名，這會導致嚴重的流涎和拒絕服藥，特別是在貓身上。對於貓科病患，通常首選調配的苯甲酸甲硝唑 (metronidazole benzoate)，因為它在唾液中的溶解度較低，因此苦味較輕。
作用機制: 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.
各物種劑量
- 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
給藥途徑
禁忌症
- 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)
不良反應
- 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)
藥物相互作用
- 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
監測
- 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)
過量
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.
VetSheet 藥物參考供持牌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方最新藥品說明書。