Cloxacillin for Abscess Treatment
Primary Treatment Recommendation
For simple cutaneous abscesses, incision and drainage is the primary treatment and is often adequate without antibiotics; however, cloxacillin is an appropriate antibiotic choice when systemic therapy is indicated for methicillin-susceptible Staphylococcus aureus (MSSA) infections, particularly in cases with systemic signs of infection, extensive disease, or failed drainage alone. 1
When Antibiotics Are Indicated for Abscesses
Antibiotic therapy should be added to incision and drainage in the following situations:
- Severe or extensive disease involving multiple sites of infection 1
- Rapid progression with associated cellulitis 1
- Signs and symptoms of systemic illness (fever, tachycardia, SIRS criteria) 1, 2
- Associated comorbidities or immunosuppression (diabetes, HIV/AIDS, malignancy) 1
- Extremes of age 1
- Abscess in difficult-to-drain locations (face, hand, genitalia) 1
- Lack of response to incision and drainage alone 1, 2
Cloxacillin Dosing and Administration
For MSSA Infections:
- Adults: 12 g/day IV divided in 4-6 doses for serious infections 1
- Alternative oral dosing: 500 mg PO four times daily 1
- Pediatric: 50 mg/kg/dose IV every 6 hours 1
The consensus pharmacokinetic target is to maintain drug levels above the MIC for at least 40-50% of the dosing interval, which is achieved with 2g infusions per day or four infusions of 3g per day in adults. 3
Cloxacillin's Role in Staphylococcal Infections
Cloxacillin (and other penicillinase-resistant penicillins like flucloxacillin, oxacillin) are the preferred first-line agents for all methicillin-susceptible staphylococcal infections because of their bactericidal activity, excellent tissue distribution, and narrow spectrum that minimizes selection pressure for resistance. 4, 5, 3
- Cloxacillin is specifically active against penicillinase-producing Staphylococcus species that would be resistant to standard penicillin 4
- Research demonstrates that cloxacillin achieves superior outcomes compared to broader-spectrum cephalosporins for MSSA bacteremia, with lower mortality rates 6
- Cloxacillin has proven efficacy in serious staphylococcal infections including CNS infections, endocarditis, and deep abscesses when used in adequate doses (≥12g/day for severe infections) 7
Important Clinical Considerations
When NOT to Use Cloxacillin:
- MRSA infections: Cloxacillin is ineffective against methicillin-resistant S. aureus; use vancomycin, linezolid, daptomycin, or TMP-SMX instead 1, 2
- Empirical therapy for purulent cellulitis/abscesses in areas with high MRSA prevalence: Consider anti-MRSA agents (clindamycin, TMP-SMX, doxycycline) until cultures confirm MSSA 1, 2
- Streptococcal infections: While cloxacillin has some activity, it is not optimal for β-hemolytic streptococci; consider adding or switching to penicillin or amoxicillin if streptococcal infection is suspected 1
Duration of Therapy:
- Simple abscesses with adequate drainage: 5-10 days 1, 2
- Complicated infections or bacteremia: 4-6 weeks depending on source control 5, 7
- Extend therapy if infection has not improved within the initial treatment period 1
Common Pitfalls to Avoid
- Do not rely solely on antibiotics without adequate surgical drainage for abscesses—drainage is the cornerstone of treatment 1, 8, 2
- Do not use inadequate doses for serious infections—doses of ≤6g/day are associated with treatment failure; use ≥12g/day for severe MSSA infections 7
- Do not assume all staphylococcal infections are MSSA—obtain cultures before starting therapy, especially in healthcare-associated infections or areas with high MRSA prevalence 1, 2
- Do not use cloxacillin empirically for abscesses in injection drug users or those with nasal MRSA colonization—these populations have higher MRSA rates and require anti-MRSA coverage 1
- Food decreases absorption of oral cloxacillin—administer on an empty stomach for optimal bioavailability 4