What medicine is used to treat infections?

Antibiotics Are the Primary Medicine Used to Treat Infections

Antibiotics are the cornerstone of treatment for bacterial infections, with selection based on the infection site, severity, likely pathogens, and local resistance patterns. 1

Selection Framework by Infection Type

Respiratory Tract Infections

• Upper respiratory (sinusitis): First-line treatment includes amoxicillin-clavulanate, second-generation cephalosporins (cefuroxime-axetil), or third-generation cephalosporins (cefpodoxime-proxetil, cefotiam-hexetil) 1
• Community-acquired pneumonia (hospitalized): Non-antipseudomonal third-generation cephalosporin (ceftriaxone or cefotaxime) plus a macrolide, or respiratory fluoroquinolone (levofloxacin or moxifloxacin) monotherapy 1
• Severe pneumonia with Pseudomonas risk: Antipseudomonal cephalosporin or carbapenem plus ciprofloxacin, OR plus macrolide and aminoglycoside 1

Urinary Tract Infections

• Complicated UTI with systemic symptoms: Amoxicillin plus aminoglycoside, OR second-generation cephalosporin plus aminoglycoside, OR intravenous third-generation cephalosporin 1
• Ciprofloxacin: Only use if local resistance <10%, entire treatment is oral, patient doesn't require hospitalization, or has anaphylaxis to β-lactams 1
• Duration: 7-14 days (14 days for men when prostatitis cannot be excluded) 1

Skin and Soft Tissue Infections

• Mild infections: Amoxicillin-clavulanate as first choice, with cloxacillin or cefalexin as alternatives 2
• Suspected MRSA (mild): Sulfamethoxazole-trimethoprim 2
• Moderate to severe with MRSA: Linezolid, daptomycin, or vancomycin 2
• Suspected Pseudomonas: Piperacillin-tazobactam, ceftazidime, cefepime, or carbapenems 2

Sexually Transmitted Infections

• Chlamydia: Azithromycin 1g orally single dose OR doxycycline 100mg orally twice daily for 7 days 1
• Alternative regimens: Erythromycin base 500mg four times daily for 7 days, OR ofloxacin 300mg twice daily for 7 days 1
• Abstinence required: 7 days after single-dose therapy or until completion of 7-day regimen 1

Prosthetic Joint Infections

• Staphylococcal PJI: 2-6 weeks pathogen-specific IV therapy plus rifampin 300-450mg orally twice daily, followed by rifampin plus oral companion drug for 3 months (hip) or 6 months (knee) 1
• Rifampin companion drugs: Ciprofloxacin or levofloxacin preferred; alternatives include co-trimoxazole, minocycline/doxycycline, or cephalexin 1

Multidrug-Resistant Gram-Negative Infections

• Carbapenem-resistant Enterobacteriaceae (CRE): Ceftazidime-avibactam, meropenem-vaborbactam, or cefiderocol for severe infections 1
• CRE with metallo-β-lactamases: Aztreonam plus ceftazidime-avibactam combination therapy 1
• Carbapenem-resistant Pseudomonas: Ceftolozane-tazobactam if active in vitro 1

Wound Infections

• Animal bites: Amoxicillin-clavulanate 875/125mg PO twice daily (oral) or ampicillin-sulbactam (IV) 2, 3
• Human bites: Amoxicillin-clavulanate or ampicillin-sulbactam 2, 3
• Necrotizing fasciitis: Clindamycin plus piperacillin-tazobactam (with or without vancomycin), OR ceftriaxone plus metronidazole (with or without vancomycin) 2

Critical Treatment Principles

Timing and Duration

• Prophylactic antibiotics: Administer within 60 minutes before surgical incision or immediately after bite injury 3
• Uncomplicated infections: Short-course therapy ≤24 hours with adequate source control 2
• Complicated infections: Continue until clinical improvement, typically 5-7 days 2
• Avoid prolonged therapy: Increases resistance risk without additional benefit when source control achieved 2

Special Population Considerations

• Elderly patients: Avoid fluoroquinolones due to tendinopathy, CNS effects, and QT prolongation risk 2, 3
• Elderly with aminoglycosides: Increased nephrotoxicity and ototoxicity risk 2
• Children with gram-negative risk: Consider second- or third-generation cephalosporins 4
• HIV-infected patients: Same treatment regimens as HIV-negative patients for most infections 1

Resistance Patterns and Stewardship

• MRSA prevalence: Dictates empiric coverage decisions in skin/soft tissue and respiratory infections 1, 2
• Fluoroquinolone restrictions: Do not use empirically if patient used fluoroquinolones in last 6 months or local resistance >10% 1
• Culture-guided therapy: Obtain cultures before antibiotics when treating established infections, then tailor therapy 3

Essential Non-Antibiotic Interventions

Surgical Management

• Wound irrigation and debridement: More important than antibiotics alone; substantially decreases infection incidence 3
• Abscess management: Incision and drainage required; simple abscesses may not need antibiotics 1
• Prosthetic joint infections: Surgical debridement essential alongside antibiotic therapy 1

Supportive Measures

• Tetanus prophylaxis: If >10 years since last dose for clean wounds, >5 years for dirty wounds 3
• Partner treatment: Simultaneous treatment of sexual partners for STIs to prevent reinfection 1
• Catheter removal: Remove indwelling catheters when feasible for catheter-associated UTIs 1

Critical Pitfalls to Avoid

• Never close bite wounds primarily except facial wounds (which require copious irrigation, cautious debridement, and preemptive antibiotics) 3
• First-generation cephalosporins inadequate for human bites (miss Eikenella corrodens) 3
• Rifampin monotherapy contraindicated for any infection; always use with companion drug 1
• High-pressure irrigation spreads bacteria into deeper tissues; use appropriate pressure only 3
• Vancomycin dosing critical: 30-60mg/kg/day IV in divided doses for serious MRSA infections, with loading dose of 25-30mg/kg for seriously ill patients 1