Nitroimidazoles

WIKIDRUGS ANTIBIOTICS

These are hetrocyclic compounds that are used as both antibiotic and anti-protozoal treatments. The main drugs in use are metronidazole, carnidazole and ronidazole.

Mechanism of Action

These drugs are bactericidal and concentration dependent killers and work by forming unstable products inside cells under anaerobic conditions.

Spectrum of Activity

• Will kill nearly all anaerobic Gram-positive and negative bacteria.
• Highly active against anaerobic protozoa, especially Treponema hyodysenteriae, Trichomonas foetus, Histomonas and Giardia.

Pharmacokinetic Considerations

They are small, lipid soluble molecules that are readily absorbed by the gastrointestinal tract. As such they have fantastic tissue penetration and can enter exclusive tissue such as the brain and the CSF. It is metabolised in the liver and 2/3 of the dose is then excreted in urine.

Side Effects and Contraindications

• Not approved in food producing animals because of mutagenicity - in the UK this means that their is no safe withdrawal period and must never be used in food producing animals.
• If metronidazole is injected subcutaneously or intramuscularly necrosis can result at the injection site.
• Acute CNS toxicity has been reported in dogs.
• Use carefully and at low doses with pregnant animals because of possible mutagenic effects.