Oxacillin sodium

Oxacillin sodium is a semi-synthetic penicillin antibiotic, closely related to methicillin, and is used to treat infections caused by penicillinase-producing Staphylococcus species. It is a beta-lactam antibiotic that inhibits the synthesis of the bacterial cell wall, leading to cell lysis and death. Oxacillin sodium is particularly effective against Staphylococcus aureus, including strains that are resistant to methicillin (MRSA). However, its use is generally restricted to infections caused by susceptible strains due to the emergence of resistance.

Mechanism of Action

Oxacillin sodium works by binding to penicillin-binding proteins (PBPs) located inside the bacterial cell wall. This binding inhibits the final transpeptidation step of peptidoglycan synthesis in bacterial cell walls, thus inhibiting cell wall biosynthesis. The weakened cell wall becomes osmotically unstable, leading to cell lysis and death. This mechanism is similar to other beta-lactam antibiotics but oxacillin sodium is resistant to degradation by beta-lactamase enzymes produced by some bacteria, which is why it is effective against penicillinase-producing strains.

Pharmacokinetics

After administration, oxacillin sodium is absorbed and distributed widely in the body, including in the bones, heart, kidneys, and liver. It can also cross the placenta and appear in breast milk. The drug is metabolized in the liver and excreted primarily by the kidneys. Its half-life allows for multiple dosing intervals throughout the day to maintain effective drug levels in the bloodstream.

Clinical Uses

Oxacillin sodium is used to treat a variety of infections caused by susceptible Gram-positive bacteria, including:

• Endocarditis
• Pneumonia
• Skin and Soft Tissue Infections
• Osteomyelitis

It is important to note that oxacillin sodium is not effective against Gram-negative bacteria or methicillin-resistant Staphylococcus aureus (MRSA).

Side Effects

Common side effects of oxacillin sodium include:

• Nausea
• Vomiting
• Diarrhea
• Rash

More serious side effects can occur, such as allergic reactions, including anaphylaxis, and liver toxicity. Monitoring of liver function tests is recommended during prolonged therapy.

Resistance

The emergence of bacterial resistance to oxacillin sodium, particularly among Staphylococcus aureus strains, is a significant concern. Resistance mechanisms include the production of altered penicillin-binding proteins (PBPs) with reduced affinity for the drug. The use of oxacillin sodium should be guided by susceptibility testing to ensure effectiveness against the infecting strain.

Conclusion

Oxacillin sodium remains an important antibiotic for the treatment of infections caused by penicillinase-producing Staphylococcus species. However, the emergence of resistance and the availability of alternative therapies may limit its use. Appropriate use, guided by susceptibility testing, is essential to preserve its efficacy.