Метициллин

Antibacterial.

ChEBI: A penicillin that is 6-aminopenicillanic acid in which one of the amino hydrogens is replaced by a 2,6-dimethoxybenzoyl group.

2,6-Dimethoxyphenylpenicillin; methicillin (international non-proprietary name). The first β-lactamase-resistant semisynthetic penicillin. It was initially used widely but has been superseded by other group 3 members and is no longer commercially available.
It is less active than benzylpenicillin or other group 3 penicillins. It is very stable to staphylococcal β-lactamase and is active against β-lactamaseproducing strains of Staph. aureus that do not produce a functional PBP 2a. Resistance is common among staphylococci, with the incidence geographically diverse. Most methicillin-resistant staphylococcal isolates display multiresistance.
It is not acid resistant, and must therefore be administered parenterally. About 10% is metabolized, with 60–80% of the dose excreted in the urine. Toxicity is similar to that of other group 3 penicillins. Nephritis appears to be more common than with other penicillins.

Like other semisynthetic penicillins, methicillin exhibits an antibacterial effect similar to that of benzylpenicillin. The main difference between methicillin and benzylpenicillin is that it is not inactivated by the enzyme penicillinase, and therefore it is effective with respect to agents producing this enzyme (staphylococci). It is used for infections caused by benzylpenicillinresistant staphylococci (septicemia, pneumonia, empyemia, osteomyelitis, abscesses, infected wounds, and others). Synonyms of this drug are cinopenil, celbenin, staphcillin, and others.