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==Mechanism of Action==
==Mechanism of Action==
Chloramphenicol works by inhibiting the transpeptidation of the peptide chain, during protein synthesis on the ribosomes. This will limit the growth and replication of bacteria but will not kill the bacteria so is a '''bacteriostatic''' antibiotic.
==Spectrum of Activity==
==Spectrum of Activity==
*It is a broad spectrum antibiotic active against most gram-positives, many gram-negatives and all anaerobes. It is also active against rickettsia and chlamydophilia.
*''Pseudomonas'' and mycobacteria species are resistant.
==Pharmacokinetic Considerations==
==Pharmacokinetic Considerations==
They are very lipophilic neutral small molecules, which are orally active and have a very wide volume of distribution. It is thus capable of penetrating cell membranes and will enter the CSF. It is eliminated in the liver via hepatic metabolism with only 10% being excreted in the urine unchanges. The half-life varies between each species and also with age of the animal.
==Side Effects and Contraindications==
==Side Effects and Contraindications==
* A reversible suppression of haematopoiesis occurs in cats when recieving high doses. It's use in cats should be limited to seven days.
* Myocardial depression has been noticed following intravenous administration.
* If it is given per os dogs and cats often have gastrointestinal irritation.
* In man a fatal aplastic anaemia can occur, this has had severe implications on the veterinary world. In the EU it is no '''banned in all producing animals in all of its forms''' (ie has no safe withdrawal period) to ensure it doesn't enter the food chain. The only liscensed veterinary products are currently topical eye medication and off-shelf use of human oral and parenteral products in non-food producing animals.
==Florfenicol and Thiamphenicol==
==Florfenicol and Thiamphenicol==
These are both analogues of chloramphenicol with similar antibacterial activity. With these a higher percentage of drug is excreted unchanged in the urine.
Most importantly though they aren't associated with aplastic anaemia in man and so are authorised to be used in food-producing animals.