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| 6-(2,6-dimethoxybenzamido)-3,3-dimethyl- 7-oxo-4-thia-1-azabicyclo*heptane- 2-carboxylic acid | |
| CAS number 61-32-5 | ATC code J01CF03 |
| PubChem CID 6087 | DrugBank n/a |
| Chemical formula | C17H20N2O6S |
| Molecular weight | 380.42 |
| Bioavailability | ? (not orally-absorbed) |
| Metabolism | hepatic, 20–40% |
| Elimination half-life | 25–60 minutes |
| Excretion | renal |
| Pregnancy category | ? |
| Legal status | ? |
| Routes of administration | IV |
Mode of action
Main article: Beta-lactam antibiotic
Like other β-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.
Medicinal chemistry
Methicillin is insensitive to beta-lactamase (also known as penicillinase) enzymes secreted by many penicillin-resistant bacteria. The presence of the ortho-dimethoxyphenyl group directly attached to the side chain carbonyl group of the penicillin nucleus facilitates the β-lactamase resistance, since those enzymes are relatively intolerant of side-chain steric hindrance. Thus it is able to bind to penicillin binding proteins (PBPs) and inhibit peptidoglycan crosslinking, but is not bound by or inactivated by β-lactamases.
Clinical use
Methicillin is not commonly used in clinical practice, but serves a purpose in the laboratory to determine antibiotic sensitivity in microbiological culture. Methicillin was previously used to treat infections caused by susceptible Gram-positive bacteria. It is unstable in the presence of gastric acid, with a degradation half-life of 5 minutes at pH 2, so it must be administered by injection. (Mitscher, 2002)
See also
References
- Mitscher LA. Antibiotics and antimicrobial agents. In: Williams DA, Lemke TL, editors. Foye's Principles of medicinal chemistry, 5th edition. Philadelphia: Lippincott Williams & Wilkins; 2002.
"Methicillin"