A 32-year-old man sustains a 40% TBSA deep partial-thickness burn to his trunk and lower limbs in a factory accident. He is alert, haemodynamically stable after initial fluid resuscitation, and has no inhalation injury. Which drug is indicated for systemic infection prophylaxis in this patient?

Explanation

## Topical Antimicrobial Choice in Burns **Key Point:** Silver sulfadiazine is the gold-standard topical antimicrobial for burn wound prophylaxis in deep partial-thickness and full-thickness burns ≥15–20% TBSA. ### Mechanism of Action Silver sulfadiazine acts as a broad-spectrum antimicrobial by releasing Ag⁺ ions, which inhibit bacterial cell wall synthesis and DNA replication. It is effective against gram-positive, gram-negative, and some fungal organisms. ### Advantages of Silver Sulfadiazine - Broad-spectrum coverage (including *Pseudomonas aeruginosa* and *Staphylococcus aureus*) - Painless application - Does not interfere with wound epithelialization - Penetrates eschar moderately well - Cost-effective and widely available - Can be used on face and perineum **High-Yield:** Silver sulfadiazine is applied once or twice daily to a thickness of 3–5 mm after gentle cleansing and debridement. ### Comparison with Other Topical Agents | Agent | Spectrum | Penetration | Drawback | Use | |-------|----------|-------------|----------|-----| | Silver sulfadiazine | Broad | Moderate | Hypersensitivity (rare) | First-line, all burn depths | | Mafenide acetate | Broad | Excellent (eschar) | Painful, metabolic acidosis, hypersensitivity | Cartilage burns (ear, nose) | | Povidone-iodine | Broad | Poor | Iodine absorption, thyroid suppression | Short-term use only | | Chlorhexidine | Broad | Poor | Cytotoxic to fibroblasts | Not recommended for burns | **Clinical Pearl:** Mafenide acetate, despite superior eschar penetration, is reserved for burns involving cartilage (ears, nose) because it causes pain on application and systemic metabolic acidosis. Silver sulfadiazine remains the first-line agent for trunk and limb burns. **Warning:** Povidone-iodine and chlorhexidine are NOT recommended for routine burn prophylaxis — iodine is absorbed systemically and suppresses thyroid function, and chlorhexidine is cytotoxic to healing tissues.