Methicillin Sodium

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Cat Number

API0231600

CAS Number

7246-14-2

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Product Detail Description Scientific Support Customer Q&A

CAS Number

7246-14-2

EINECS

205-083-9

Storage

Store at 2-8℃

Synonyms

Sodium methicillin; SQ 16,123; BRL-1241; AO9YF4MN30; Meticillin sodium monohydrate; Sodium methicillin monohydrate; Celbenin

Molecular Formula

C17H21N2NaO7S

Molecular Weight

420.4

Smiles

CC1([C@@H](N2[C@H](S1)[C@@H](C2=O)NC(=O)C3=C(C=CC=C3OC)OC)C(=O)[O-])C.O.[Na+]

Appearance

White to off-white powder

Melting Point

196-197℃

Boiling Point

640℃

General Description

Methicillin sodium is a semisynthetic penicillinase-resistant beta-lactam antibiotic developed specifically to treat infections caused by penicillinase-producing staphylococci.

Mechanism of Action

Like other beta-lactams, methicillin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), particularly PBP2a in susceptible strains. The drug's dimethoxyphenyl side chain provides steric hindrance that prevents hydrolysis by staphylococcal beta-lactamase (penicillinase). However, MRSA strains possess the mecA gene encoding PBP2a, which has low affinity for methicillin, rendering the drug ineffective.

Application

Methicillin was historically the drug of choice for serious staphylococcal infections, including bacteremia, pneumonia, and osteomyelitis caused by penicillinase-producing S. aureus. Today, methicillin serves only as a reference agent for defining MRSA resistance patterns.

A phenotypically methicillin‑resistant S. aureus (MRSA) isolate obtained during cefoxitin‑based nasal screening tested negative for mecA, mecC, and SCCmec‑orfX. Instead, it carried a mecB gene previously described in Macrococcus caseolyticus. The gene was flanked by β‑lactam regulatory genes and located on an 84.6‑kb multidrug‑resistance plasmid also encoding aminoglycoside, macrolide, and tetracycline resistance. This novel plasmid‑borne β‑lactam resistance mechanism could accelerate MRSA spread and render β‑lactams broadly ineffective, posing a significant therapeutic challenge.

Fig. 1 Circular map of the mecB-carrying plasmid pSAWWU4229_1 from Staphylococcus aureus isolate UKM4229. (Becker K, et al., 2018)

References

Becker K, et al. Plasmid-Encoded Transferable mecB-Mediated Methicillin Resistance in Staphylococcus aureus. Emerg Infect Dis. 2018;24(2):242-248.

Does Methicillin Sodium require refrigerated storage as a penicillinase-resistant penicillin?

Yes, it must be stored at 2-8°C. At room temperature, rapid hydrolysis of the beta-lactam ring and degradation of the dimethoxyphenyl side chain occur.

Is Methicillin Sodium extremely sensitive to moisture, and how is this prevented?

Yes, it is highly hygroscopic. Our packaging includes moisture-barrier vials or foil bags with desiccant, and the material should be opened only in low-humidity environments.

What is the stability of Methicillin Sodium after reconstitution for injection?

Reconstituted solutions have very limited stability (typically 24 hours under refrigeration). We provide detailed in-use stability data for various diluents.

How is the impurity methicilloic acid monitored during stability?

This primary hydrolysis product is specifically quantified using a stability-indicating HPLC method, ensuring it remains below pharmacopoeial limits.