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yorkiegirl2 · 09-06-2006, 06:22 AM

Metronidazole
Metronidazole is used in small animals for treating giardiasis, trichomoniasis, and certain anaerobic infections. It appears that most neurotoxicoses in dogs and cats result from long term administration, and usually at high dose rates (e.g., exceeding 66 mg/kg/day, in dogs) [1]. In one report, five dogs receiving metronidazole at doses ranging from 67 to 129 mg/kg of body weight per day, for 3 to 14 days, showed signs of acute neurological dysfunction severe generalized ataxia and vertical, positional nystagmus, usually preceded by anorexia and intermittent vomiting [118]. Increased levels of protein were noted in 2 of 3 dogs from which CSF was collected. Two dogs were euthanatized because of severe neurological dysfunction. Three dogs slowly improved and eventually recovered completely after several months. Axonal degeneration was seen in vestibular tracts of one dog, while bilateral leukomalacia was found in another dog near the radix of the vestibular nerve. It was concluded that currently recommended dosages of metronidazole for dogs were excessive, and a total daily dosage of 30 mg/kg was recommended [118]. In another report involving a 2 year old Plott Hound-cross dog (receiving metronidazole at 89.5 mg/kg/day for 5 weeks) with progressive ataxia, nystagmus and knuckling, who was disoriented, had intermittent excitatory episodes, consisting of paddling, muscle spasms and vocalization, with involuntary urination during defecation, neurological abnormalities were reversed within 2 weeks after discontinuation of metronidazole therapy [119]. Interestingly, in a recent report from Sweden, adverse CNS signs were associated mainly with metronidazole administration to Collies [120]. In one retrospective study involving 20 dogs with metronidazole toxicosis (ranging from 60 - 65 mg/kg over 37 - 45 days), recovery was enhanced by administration of diazepam (the average intravenous/oral dosage was 0.43 mg/kg tid for 3 days) [212]. It was postulated that this positive effect might result from diazepam competitively displacing metronidazole from GABA receptors. In cats, receiving metronidazole from 58 to 222 mg/kg, daily, for up to 6 months, neurological abnormalities seen include disorientation, ataxia, seizures, and blindness [121,122]. The neurological signs in all cats resolved within days of initiating supportive therapy and withdrawal of the drug.

09-06-2006, 06:22 AM	#8
yorkiegirl2 YT 2000 Club Member Join Date: Apr 2005 Location: Missouri Posts: 2,394	page 8 Metronidazole Metronidazole is used in small animals for treating giardiasis, trichomoniasis, and certain anaerobic infections. It appears that most neurotoxicoses in dogs and cats result from long term administration, and usually at high dose rates (e.g., exceeding 66 mg/kg/day, in dogs) [1]. In one report, five dogs receiving metronidazole at doses ranging from 67 to 129 mg/kg of body weight per day, for 3 to 14 days, showed signs of acute neurological dysfunction severe generalized ataxia and vertical, positional nystagmus, usually preceded by anorexia and intermittent vomiting [118]. Increased levels of protein were noted in 2 of 3 dogs from which CSF was collected. Two dogs were euthanatized because of severe neurological dysfunction. Three dogs slowly improved and eventually recovered completely after several months. Axonal degeneration was seen in vestibular tracts of one dog, while bilateral leukomalacia was found in another dog near the radix of the vestibular nerve. It was concluded that currently recommended dosages of metronidazole for dogs were excessive, and a total daily dosage of 30 mg/kg was recommended [118]. In another report involving a 2 year old Plott Hound-cross dog (receiving metronidazole at 89.5 mg/kg/day for 5 weeks) with progressive ataxia, nystagmus and knuckling, who was disoriented, had intermittent excitatory episodes, consisting of paddling, muscle spasms and vocalization, with involuntary urination during defecation, neurological abnormalities were reversed within 2 weeks after discontinuation of metronidazole therapy [119]. Interestingly, in a recent report from Sweden, adverse CNS signs were associated mainly with metronidazole administration to Collies [120]. In one retrospective study involving 20 dogs with metronidazole toxicosis (ranging from 60 - 65 mg/kg over 37 - 45 days), recovery was enhanced by administration of diazepam (the average intravenous/oral dosage was 0.43 mg/kg tid for 3 days) [212]. It was postulated that this positive effect might result from diazepam competitively displacing metronidazole from GABA receptors. In cats, receiving metronidazole from 58 to 222 mg/kg, daily, for up to 6 months, neurological abnormalities seen include disorientation, ataxia, seizures, and blindness [121,122]. The neurological signs in all cats resolved within days of initiating supportive therapy and withdrawal of the drug.