Cloxacillin: A Penicillinase-Resistant Antibiotic

Cloxacillin is a narrow-spectrum beta-lactam antibiotic specifically designed to combat penicillinase-producing staphylococci. It's primarily used for skin infections, osteomyelitis, and other infections caused by susceptible gram-positive bacteria.

Mechanism of Action

Cloxacillin works by inhibiting bacterial cell wall synthesis. Its unique structure resists degradation by staphylococcal penicillinase enzymes, making it effective against many penicillin-resistant strains.

Available Formulations

This antibiotic comes in oral capsules (250mg, 500mg) and injectable forms. The oral suspension must be reconstituted before use and has limited stability after preparation.

Common Adverse Effects

Gastrointestinal upset, allergic reactions, and occasional liver enzyme elevations may occur. Severe hypersensitivity requires immediate medical attention.

Resistance Considerations

While resistant to many staphylococcal penicillinases, MRSA strains are unaffected. Culture and sensitivity testing guide appropriate use.

Storage Requirements

Capsules should be stored below 25°C. Injectable forms require refrigeration. Always check expiration dates before administration.

Cloxacillin vs Other Antibiotics

Compared to broader-spectrum penicillins, cloxacillin targets specifically staphylococcal infections. It's less effective than vancomycin for MRSA but has fewer side effects.

Contraindications

Patients with penicillin allergy should avoid cloxacillin. Caution is needed in hepatic impairment due to biliary excretion.

Use in Special Populations

Pregnancy category B - use only if clearly needed. Small amounts appear in breast milk, requiring risk-benefit assessment.

Drug Interactions

Probenecid may increase cloxacillin levels. Oral contraceptives may be less effective - recommend backup methods.

Administration Guidelines

Take on empty stomach (1 hour before or 2 hours after meals) with water. Space doses evenly around the clock.

Treatment Duration

Typically 7-14 days depending on infection severity. Continue for at least 48 hours after symptoms resolve.

What infections does cloxacillin treat?

Cloxacillin is effective against penicillinase-producing staphylococcal infections including cellulitis, abscesses, and infected wounds. It's not effective against MRSA or gram-negative bacteria.

How does cloxacillin differ from flucloxacillin?

Flucloxacillin has better oral absorption but similar spectrum. Some countries prefer one over the other based on local resistance patterns.

Can cloxacillin cause diarrhea?

Yes, like all antibiotics it may disrupt gut flora. Severe diarrhea could indicate pseudomembranous colitis requiring immediate care.

Is cloxacillin safe for children?

Yes, in appropriate weight-based doses. The oral suspension is often used for pediatric patients.

What should I do if I miss a dose?

Take it as soon as remembered unless close to next dose. Never double doses to make up for missed ones.

Does cloxacillin interact with food?

Food decreases absorption significantly. Always take on empty stomach for maximum effectiveness.

Report any unusual bruising or bleeding to your healthcare provider immediately.

How long does cloxacillin take to work?

Clinical improvement is typically seen within 2-3 days for skin infections. Deep-seated infections may require longer treatment.

What are signs of allergic reaction?

Rash, itching, swelling (especially of face/tongue), severe dizziness, or trouble breathing require emergency care.

Can I drink alcohol with cloxacillin?

Moderate alcohol is unlikely to interact but may increase gastrointestinal side effects. Heavy drinking should be avoided.

Why must doses be spaced evenly?

Maintaining consistent drug levels is crucial for effectiveness. Irregular dosing promotes bacterial resistance.

What storage conditions are required?

Capsules: room temperature. Suspension: refrigerate after mixing and discard after 14 days. Avoid freezing.

Can cloxacillin treat UTIs?

Only if caused by susceptible staphylococci. Most UTIs require different antibiotics as they're typically gram-negative.

Always complete the full prescribed course unless instructed otherwise.