A 32-year-old woman presents with acute suppurative infection of the breast (acute mastitis) with localized abscess formation. She is febrile (38.5°C) and has purulent discharge. Culture is pending. What is the drug of choice for empiric treatment?

Explanation

## Drug of Choice for Acute Suppurative Mastitis ### Clinical Context Acute mastitis with abscess formation is typically caused by **Staphylococcus aureus** (most common) and occasionally Streptococcus pyogenes. The infection is community-acquired and usually methicillin-sensitive (MSSA). ### Why Cloxacillin is First-Line **Key Point:** Cloxacillin (or flucloxacillin in some regions) is the drug of choice for MSSA-associated acute suppurative infections because it is a beta-lactamase-resistant penicillin with excellent tissue penetration into breast tissue and abscess cavities. **High-Yield:** Cloxacillin achieves high concentrations in breast tissue and pus, making it ideal for localized suppurative infections. It covers MSSA reliably and has a long track record of clinical efficacy in acute mastitis. **Clinical Pearl:** In India, cloxacillin (500 mg IV/IM 6-hourly or 500 mg oral QID) is the standard empiric choice for community-acquired staphylococcal skin and soft tissue infections, including acute mastitis, pending culture results. ### Dosing & Duration - **IV/IM:** 500 mg–1 g 6-hourly - **Oral:** 500 mg 6-hourly (for milder cases or step-down) - **Duration:** 10–14 days; may require surgical drainage if abscess is large (>2 cm) ### Comparison with Other Options | Drug | Indication | Limitation | |------|-----------|----------| | **Cloxacillin** | MSSA skin/soft tissue, mastitis | Not for MRSA | | Ceftriaxone | Gram-negative coverage, meningitis | Inferior for MSSA skin infections; overkill | | Vancomycin | MRSA, severe infections | Reserved for MRSA or beta-lactam allergy; not first-line for MSSA | | Fluoroquinolone | Gram-negative UTI, respiratory | Poor beta-lactamase-resistant coverage; not reliable for staphylococcal abscess | **Warning:** Do NOT use cephalosporins as monotherapy for staphylococcal abscess unless MRSA is suspected — they are less reliable than beta-lactamase-resistant penicillins for MSSA. [cite:Robbins 10e Ch 3]