Floxacillin

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Floxacillin is a beta-lactam antibiotic of the penicillin class. It is used to treat infections caused by Gram-positive bacteria, particularly those caused by Staphylococcus aureus. Floxacillin is resistant to beta-lactamase enzymes produced by some bacteria, which makes it effective against penicillin-resistant strains.

Pharmacology

Mechanism of Action

Floxacillin works by inhibiting the synthesis of bacterial cell walls. It binds to penicillin-binding proteins (PBPs) located inside the bacterial cell wall, which are essential for the cross-linking of the peptidoglycan layer. This inhibition leads to the weakening of the cell wall and eventually causes cell lysis and death of the bacterium.

Pharmacokinetics

Floxacillin is administered either orally or intravenously. It has a bioavailability of approximately 50% when taken orally. The drug is highly protein-bound, with about 95% of the drug bound to plasma proteins. Floxacillin is metabolized in the liver and has an elimination half-life of approximately 1 hour. It is primarily excreted through the kidneys.

Clinical Use

Indications

Floxacillin is indicated for the treatment of infections caused by penicillinase-producing staphylococci and other susceptible organisms. Common indications include:

• Skin and soft tissue infections
• Bone and joint infections
• Respiratory tract infections
• Endocarditis

Dosage

The dosage of floxacillin varies depending on the severity and type of infection, as well as the patient's age and renal function. Typical adult doses range from 250 mg to 500 mg every 6 hours. For severe infections, higher doses may be required.

Adverse Effects

Common Side Effects

• Gastrointestinal disturbances such as nausea, vomiting, and diarrhea
• Rash
• Urticaria

Serious Side Effects

• Anaphylaxis
• Hepatotoxicity
• Neutropenia

Contraindications

Floxacillin is contraindicated in patients with a known hypersensitivity to penicillins or any component of the formulation. Caution is advised in patients with a history of allergic reactions to cephalosporins.

Interactions

Floxacillin may interact with other medications, including:

• Probenecid: May increase serum levels of floxacillin
• Methotrexate: Floxacillin may reduce the renal clearance of methotrexate

Special Populations

Pregnancy and Lactation

Floxacillin is classified as pregnancy category B1 in Australia and category B in the United States, indicating that there is no evidence of harm to the fetus in animal studies, but human studies are lacking. Floxacillin is excreted in breast milk, and caution is advised when administering to breastfeeding mothers.

Renal Impairment

Dose adjustment may be necessary in patients with renal impairment, as floxacillin is primarily excreted by the kidneys.

See Also

• Antibiotic resistance
• Beta-lactam antibiotics
• Staphylococcus aureus

External Links

• Drugs.com
• MedicineNet

Penicillin antibiotics

• penicillins first generation (natural penicillins)
  • benzathine penicillin, procaine penicillin, penicillin g, penicillin v, penicillin vk

• penicillins second generation (penicillinase-resistant penicillins)
  • cloxacillin, dicloxacillin, flucloxacillin, methicillin, nafcillin, oxacillin

• penicillins third generation (aminopenicillins)
  • amoxicillin, ampicillin, ampicillin-sulbactam, bacampicillin, pivampicillin
• see also amoxicillin-clavulanate

• penicillins fourth generation (extended-spectrum penicillins)
  • carbenicillin, mezlocillin, piperacillin, piperacillin-tazobactam, ticarcillin, ticarcillin-clavulanate