Methicillin
QJ51CF03 (WHO) | |
Pharmacokinetic data | |
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Bioavailability | Not orally absorbed |
Metabolism | hepatic, 20–40% |
Elimination half-life | 25–60 minutes |
Excretion | renal |
Identifiers | |
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Methicillin (
Methicillin was discovered in 1960.[1]
Medical uses
Compared to other penicillins that face
Spectrum of activity
At one time, methicillin was used to treat infections caused by certain gram-positive bacteria including Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, and Streptococcus pneumoniae. Methicillin is only effective against Staphylococcus aureus 50% of the time.
Resistance to methicillin is conferred by activation of a new bacterial
These susceptibility data are given on a few medically significant bacteria:
- Staphylococcus aureus: 0.125 – >100 μg/ml
- Methicillin resistant Staphylococcus aureus(MRSA): 15.6 – >1000 μg/ml
- Streptococcus pneumoniae: 0.39 μg/ml[2]
Mechanism of action
Like other beta-lactam antibiotics, methicillin acts by inhibiting the synthesis of bacterial cell walls. It inhibits cross-linkage between the linear peptidoglycan polymer chains that make up a major component of the cell wall of gram-positive bacteria. It does this by binding to and competitively inhibiting the transpeptidase enzyme (also known as penicillin-binding proteins (PBPs)). These PBPs crosslink glycopeptides (D-alanyl-alanine), forming the peptidoglycan cell wall. Methicillin and other β-lactam antibiotics are structural analogs of D-alanyl-alanine, and the transpeptidase enzymes that bind to them are sometimes called penicillin-binding proteins (PBPs).[3]
Methicillin is actually a
Medicinal chemistry
Methicillin is resistant to
History
Methicillin was developed by
Its role in therapy has been largely replaced by oxacillin (used for clinical antimicrobial susceptibility testing), flucloxacillin and dicloxacillin, but the term methicillin-resistant Staphylococcus aureus (MRSA) continues to be used to describe S. aureus strains resistant to all penicillins.[5]
References
- ISBN 9789400926592.
- ^ "Methicillin Sodium Susceptibility and Concentration (MIC) Data" (PDF). TOKU-E.
- ^ Gladwin M, Trattler B (2004). Clinical Microbiology made ridiculously simple (3rd ed.). Miami: MedMaster, Inc.
- ISBN 978-981-283-227-6. Retrieved 18 November 2010.
- PMID 15520143.