Metronidazole
Antiprotozoal
View Brand Names (9)Dose and dosage
40-50 mg/kg
Treatment of trichomoniasis (bulls): 75 mg/kg q12h IV for three doses.
For susceptible anaerobic infections:
a) 20–25 mg/kg PO q8–12h; for treatment of colitis due to Clostridium spp., may dose at 15 mg/kg PO q8h. Can also dose at same dosages rectally if unable to dose PO. Metronidazole is uncommonly associated with diarrhea and neurologic side effects. (Bentz 2007)
b) For metritis secondary to B. fragilis: 15–25 mg/kg PO q12h. (LeBlanc
2009)
c) Foals: Oral metronidazole therapy should be strongly considered for all foals with severe diarrhea as about 35% of foals tested are positive for toxins associated with clostridia. Oral metronidazole is typically administered at 15–25 mg/kg PO q8h, but doses of 25 mg/kg q12h have recently also been recommended. May also give IV; authors use a loading dose of 15 mg/kg, and then give 7.5 mg/kg q6h based on the human dose recommendation. (Corley & Hollis 2009)
d) Foals with C. perfringens: 10–15 mg/kg PO 3–4 times a day (dose depends on severity); if animal has an ileus and is intolerant of oral feeding give IV at 10 mg/kg IV 4 times a day (Slovis 2003)
e) For L. intracellularis infections: metronidazole 10–15 mg/kg PO q8– 12h with either oxytetracycline (10–18 mg/kg via slow IV q24h) or chloramphenicol (44 mg/kg PO q6–8h). (Frazer 2007)
40-50 mg/kg
40-50 mg/kg
For treatment of Giardia:
a) 15–25 mg/kg PO q12–24h daily for 5–7 days (Lappin 2006)
b) 25 mg/kg PO q12h for 7 days (Zoran 2007)
c) 22 mg/kg PO twice daily for 5 days. May be combined with fenbendazole (50 mg/kg PO once daily for 3 or 5 days) to relieve clinical signs and eliminate parasites. (Payne, 2009)
For other protozoal infections:
a) Entamoeba histolytica or Pentatrichomas hominis: 25 mg/kg PO q12h for 8 days (Lappin, 2000)
For treating H. pylori:
a) Metronidazole 10–15 mg/kg PO two times a day; clarithromycin 7.5 mg/kg PO two times a day; amoxicillin 20 mg/kg PO twice daily for 14 days (Simpson 2003)
For anaerobic infections:
a) For sepsis: 15 mg/kg IV q12h (Hall 2000)
For adjunctive therapy of GI conditions:
a) 10–20 mg/kg PO two to three times a day has been used in thetreatment of mild to moderate cases of large bowel IBD. (Washabau 2009)
b) For inflammatory bowel disease: With a change of diet to “hypoallergenic”, may give metronidazole at 62.5 mg (total dose) PO per cat once daily for 10–20 days. Resistant cats or those with severe disease are given immunosuppressive doses of prednisolone (1–2 mg/kg initially twice daily). (Gaschen 2006)
c) 10–15 mg/kg PO q8–12h; combine with prednisone to manage moderate to severe cases. (Marks 2007)
d) For hepatic encephalopathy: 7.5 mg/kg PO q8–12h (Cornelius et al. 2000)
For susceptible infections (anaerobes; giardia):
a) 10–50 mg/kg PO q12h. (Oglesbee 2009)
b) Ratites (not to be used for food): 20–25 mg/kg PO twice daily (Jenson
1998)
For anaerobic infections: 20 mg/kg PO q12h for 3–5 days or 40 mg/kg PO once daily; 5 mg/kg slow IV q12h (Ivey & Morrisey 2000)
For treatment of Giardia:
a) 15–25 mg/kg PO q12–24h daily for 5–7 days (Lappin 2006)
b) 22 mg/kg PO twice daily for 5 days. May be combined with fenbendazole (50 mg/kg PO once daily for 3 or 5 days) to relieve clinical signs and eliminate parasites. (Payne & Artzer 2009)
For other protozoal infections:
a) Entamoeba histolytica or Pentatrichomas hominis: 25 mg/kg PO q12h for 8 days (Lappin 2000)
For anaerobic infections:
a) For sepsis: 15 mg/kg IV q12h (Hardie 2000)
For eliminating Helicobacter gastritis infections:
a) Using triple therapy: Metronidazole 15.4 mg/kg q8h, amoxicillin 11 mg/kg q8h and bismuth subsalicylate (original Pepto-Bismol®) 0.22 mL/kg PO q4–6h. Give each for 3 weeks. (Hall 2000)
For adjunctive therapy of plasmacytic/lymphocytic enteritis:
a) 10–30 mg/kg PO q8–24h for 2–4 weeks in refractory cases (Leib, M.S. et al. 1989)
For Clostridium perfringens enterotoxicosis:
a) 10–20 mg/kg PO twice daily for 7–28 days. (Tams 2007)
For inflammatory bowel disease:
a) 10–20 mg/kg PO two to three times a day has been used in the treatment of mild to moderate cases of large bowel IBD. (Washabau 2009)
b) For ulcerative colitis in dogs refractory to other therapies (e.g., sulfasalazine, immunosuppressants, diet, etc.): 10–20 mg/kg PO twice daily–three times a day; may be beneficial in treating for 2–4 weeks those dogs with chronic colitis having unexplained diarrhea (Leib, M. 2000).
c) 10–15 mg/kg PO q8–12h; combine with prednisone to manage moderate to severe cases. (Marks 2007)
d) In cases of predominantly large bowel diarrhea (colitis with typical clinical presentation) if parasiticide treatment and elimination diet fail, a therapeutic trial can be made: metronidazole 20–25 mg/kg PO twice daily for 5-10 days with the addition of fiber to the diet (e.g., psyllium at 0.5 tablespoon for toy breeds, 1 tablespoon for small dogs, 2 tablespoons for medium dogs, and 3 tablespoons for large dogs. However, sampling of mucosal biopsies prior to further treatment may be the best course of action. (Gaschen 2008)
For treatment of medial canthus syndrome (tear staining):
a) 100–200 mg (total dose) PO once per day for 10 days each month.(Krohne 2008)
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Poultry: Anaerobic bacterial infections, Necrotic enteritis, ulcerative enteritis, gangrenous dermatitis etc Protozoal infection like Histomoniasis, Trichomoniasis etc and ascetic syndrome.
Pigeon: Trichomoniasis (Canker).
Dog & Cat: Anaerobic bacterial infections like meningitis, cholangitis, sepsis etc. giardiasis and other protozoal infection etc.
Metronidazole is an antibacterial and antiprotozoal drug used frequently in small animals, primarily for GI problems. It is a second-generation nitroimidazole in which the activity involves generation of free nitro radicals via metabolism within protozoa and bacteria. Metronidazole disrupts DNA in the organism via reaction with intracellular metabolite. Its action is specific for anaerobic bacteria and protozoa. Resistance is rare. It is active against some protozoa, including Trichomonas spp., Giardia spp., and intestinal protozoal parasites. It also has in vitro activity against anaerobic bacteria and Helicobacter spp.
The most severe adverse effect is caused by toxicity to the CNS. It is highly lipophilic and readily crosses the blood–brain barrier. High doses have caused lethargy, CNS depression, ataxia, tremors, seizures, vomiting, and weakness.
Fetal abnormalities have not been demonstrated in animals with recommended
doses but use cautiously during pregnancy.