Antibiotic therapy

Question 1

What is the mechanism of action of metronidazole

Answer 1

Metronidazole is not an antibiotic compound itself, but rather a pro-drug that is converted to toxic compounds via a redox reaction within anaerobic bacteria and protozoa
- The resulting compounds disrupt the helical structure of DNA within the cell, thus inhibiting nucleic acid synthesis

It also appears to modulate the animal’s cell mediated immunity (underlying reason unknown)

It is a bactericidal, concentration-dependent drug

Question 2

What are the main pharmacokinetic characteristics of metronidazole

Answer 2

It tends to be well absorbed after oral administration

It is a lipophilic drug, thus it is widely distributed in the tissues, includind the CNS

Question 3

Where is metronidazole metabolized

Answer 3

Metronidazole is primarily metabolized by the liver and its metabolites are then excreted via urine and feces

Animals with liver dysfunction should receive a 25-50% dose reduction

Question 4

What are the toxic effects of metronidazole

Answer 4

Signs of metronidazole toxicity include GI disturbances and nausea

Cats may also salivate because of the bitter taste

Neurological signs tend to occur in animals that have received an overdose
- rarely observed with doses under 15 mg/kg, q12h
- central vestibular, cerebellar, cerebral dysfunction resulting in tremors, ataxia, nystagmus, head tilt, blindness, mental dullness and seizures
- generally the signs of neurotoxicosis resolve within a week or so of withdrawal of the drug