Description and Composition of Amphenicol
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Amphenicol is a semisynthetic, broad-spectrum antibiotic derived from Streptomyces venequelae with primarily bacteriostatic activity. Chloramphenicol diffuses through the bacterial cell wall and reversibly binds to the bacterial 50S ribosomal subunit. The binding interferes with peptidyl transferase activity, thereby prevents transfer of amino acids to the growing peptide chains and blocks peptide bond formation. As a result bacterial protein synthesis is blocked and impede bacterial cell proliferation.
It’s mainly used to treat eye infections (such as conjunctivitis) and sometimes ear infections.
Amphenicol can comes as eye drops or eye ointment. These are available on prescription or to buy from pharmacies. It also comes as ear drops. These are on prescription only. It is also given intravenously (directly into a vein) or as capsules. This treatment is for serious infections and is nearly always given in hospital.
Pharmacological Actions of Amphenicol
Amphenicol is a bacteriostatic antibiotic with a broad spectrum of action against both Gram-positive and Gram-negative bacteria as well as some other organisms. Chloramphenicol is thought to enters sensitive cells by active transport process. Within the cell its bind to the 505 sub unit of the bacterial ribosome thus inhibiting bacterial protein synthesis by prevent attachment of aminoacyl transfer RNA to its receptor site on the ribosome transferase which results in it is bacteriostatic action.
Indications and Uses of Amphenicol
Amphenicol is a broad spectrum antibiotic which is effective against Gram-negative organisms including haemmophilus influenza, Salmonella typhi, streptococci staphylococci, pneumococci and gonococci), rickettsiae, chlamydias and mycoplasmas It should only be used in severe infections, such as meningitis, specticaenia or typhoid fever, when other antibiotics have failed, or when benefits outweights the risk.
Contradictions of Amphenicol
Do not use in the treatment of trivial infections. Do not use chloramphenicol in patients with severe liver function impairment or hematologic disorders. Metabolism of oral antidiabetics, phenytoin and oral anticoagulants is decreased by chloramphenicol making serious toxical possible. Dose reduction is often necessary
Amphenicol is inactivated in the liver and may, therefore, interact with drugs that are metabolised by hepatic microsomal enzymes. For example, chloramphenicol, enhances the effects of coumarin anticoagulants such as dicoumarol and warfarin sodium, some hypoglycemics such as chlorpropamide, and tolbutamide, and antiepileptics such as phenytoin and may reduce the metabolism of tacrolimus and of cyclophosphamide to its active form.
Use of Amphenicol in Pregnancy
Amphenicol should not be used during pregnancy unless absolutely necessary The “grey baby syndrome” can occur in newborns whose mothers received chloramphenicol during the last trimester of pregnancy. The syndrome is characterized by abdominal distension, cyanosis (grey colour ) and collapse within a few hours of onset of the syndromes, death may occur Breast feeding should be interrupted during treatment with chloramphenicol since toxicity in the infant cannot be excluded.
Side Effects of Amphenicol
Two types of bone marrow depression may occur. A rare, but irreversible, not Dose related type, leading to death of the patient, symptoms appears more frequently especially with prolonged treatment and/or high dosage. The “grey baby” syndrome (grey syndrome) is dose -related(see under Pregnancy and breast feeding)
Symptoms of Overdosage of Amphenicol and Treatments
Symptoms: Reversible anaemia, and other blood disorders, nausea and vomiting
May occur within a few hours of intake, emptying of stomach might be effective, Generally supportive therapy
How to Store Amphenicol
Store in a cool dry place, at not more than 30ºC
KEEP OUT OF REACH OF CHILDREN.