What is the best antibiotic for a patient who has stepped on a nail and has no signs of existing infection, considering their tetanus vaccination status and potential allergies to penicillin or amoxicillin?

Best Antibiotic for Stepping on a Nail

For a patient who has stepped on a nail without signs of infection, no prophylactic antibiotics are indicated—focus on tetanus prophylaxis, thorough wound cleansing, and close observation for infection development. 1, 2

Initial Wound Management

The most critical intervention is immediate wound care, not antibiotics:

• Perform thorough cleansing and debridement of the puncture wound, which is paramount for preventing infection 3
• Irrigate with simple saline solution without additives, as soap or antiseptics provide no additional benefit 1
• Remove any foreign material or debris from the wound 3

Tetanus Prophylaxis Priority

Tetanus prevention takes precedence over antibiotic prophylaxis:

• Administer tetanus toxoid booster if the patient's last dose was >5 years ago for contaminated wounds or >10 years for clean wounds 3
• For patients without adequate immunization history, consider tetanus immunoglobulin in addition to toxoid 3

When Antibiotics Are NOT Indicated

Prophylactic antibiotics do not prevent infection in puncture wounds and should be avoided:

• Prophylactic antibiotics are ineffective for wounds left open or treated late, as continuing contamination makes them futile 2
• Prolonged prophylactic antibiotic use only creates antibiotic-resistant infections without preventing them 2
• Clean puncture wounds without signs of infection do not require antibiotics 1

When Antibiotics ARE Indicated

Antibiotics become necessary only when clinical infection develops:

Signs of Infection Requiring Treatment:

• Local pain, swelling, erythema, and purulent drainage 1
• Fever >38.5°C or pulse >100 beats/min 1
• Cellulitis extending >2 cm from the wound 1
• Signs of deeper infection (osteochondritis) on imaging 4

Antibiotic Selection for Established Infection:

For cellulitis without systemic signs:

• Open and drain any purulent collection—this is the primary treatment 1
• If minimal surrounding cellulitis (<5 cm erythema) and minimal systemic signs, antibiotics may be unnecessary after drainage 1

For cellulitis with systemic signs or extensive involvement:

• First-line: Cefazolin or cephalexin for methicillin-susceptible Staphylococcus aureus coverage 1
• For penicillin allergy: Clindamycin 300-450 mg every 6-8 hours orally 5, 6
• Duration: 24-48 hours for mild systemic signs, or 7 days for more extensive infection 1

For suspected osteochondritis (bone involvement):

• Ciprofloxacin 750 mg twice daily orally provides excellent coverage for Pseudomonas aeruginosa, the most common pathogen in nail puncture osteochondritis 4
• Surgical debridement must be performed first—antibiotics alone are insufficient 4
• Duration: 14 days for osteochondritis, 7 days for cellulitis alone 4

Critical Pitfalls to Avoid

Common mistakes that worsen outcomes:

• Never prescribe prophylactic antibiotics for clean puncture wounds—this promotes resistance without preventing infection 2
• Do not use penicillin or amoxicillin alone—they lack adequate coverage for S. aureus, now the predominant pathogen in skin infections 7
• Avoid prolonged antibiotic courses without documented infection—this only selects for resistant organisms 2
• Do not skip surgical intervention when infection is present—antibiotics cannot substitute for drainage and debridement 1, 4

Monitoring Strategy

Close observation is more valuable than prophylactic antibiotics:

• Instruct the patient to monitor for signs of infection over 48-72 hours 1
• Return immediately if pain worsens, redness spreads, fever develops, or purulent drainage appears 1
• If infection develops, culture the wound before starting antibiotics to guide therapy 6