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[[Image: Chloramphenicol.png|thumb|right|250px|The 3D Structure of Chloramphenicol]]
[[Image: Chloramphenicol.png|thumb|right|250px|The 3D Structure of Chloramphenicol]]
==Introduction==
Chloramphenicol orginates from cultures of ''Streptomyces'' and was one of the first antibiotics to be synthetically mass-produced. It is a dichloracetic acid derivative. It's analogues florfenicol and thiamphenicol are discussed at the bottom of the page.
Chloramphenicol orginates from cultures of ''Streptomyces'' and was one of the first antibiotics to be synthetically mass-produced. It is a dichloracetic acid derivative. It's analogues florfenicol and thiamphenicol are discussed at the bottom of the page.
==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.
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.
*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.
*''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 unchanged. The half-life varies between each species and also with age of the animal.
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 unchanged. 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.
* 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.
* Myocardial depression has been noticed following intravenous administration.
==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.
These are both analogues of chloramphenicol with similar antibacterial activity. With these a higher percentage of drug is excreted unchanged in the urine.
More importantly they aren't associated with aplastic anaemia in man and so are authorised to be used in food-producing animals.
More importantly they aren't associated with aplastic anaemia in man and so are authorised to be used in food-producing animals.