Management of Anthrax
For all forms of systemic anthrax (inhalational and gastrointestinal), initiate immediate intravenous ciprofloxacin 400 mg every 12 hours OR doxycycline 100 mg every 12 hours PLUS one to two additional antimicrobials, continuing for a total of 60 days (IV then oral), as the high mortality of these forms demands aggressive multi-drug therapy. 1
Inhalational Anthrax Treatment
Initial IV therapy is critical and must include:
- Adults: Ciprofloxacin 400 mg IV every 12 hours OR doxycycline 100 mg IV every 12 hours 1
- Children: Ciprofloxacin 10-15 mg/kg IV every 12 hours (max 1 g/day) OR doxycycline (weight-based: >45 kg = 100 mg every 12 hours; <45 kg = 2.2 mg/kg every 12 hours) 1
- Pregnant women: Same regimen as non-pregnant adults—the extremely high mortality rate outweighs medication risks 1
Add one to two additional antimicrobials from: rifampin, vancomycin, imipenem, chloramphenicol, clindamycin, or clarithromycin due to the high bacterial load and mortality risk 1, 2
Critical caveats:
- Never use penicillin or ampicillin alone—B. anthracis produces constitutive and inducible beta-lactamases that render these ineffective 1
- Avoid cephalosporins and trimethoprim-sulfamethoxazole entirely—they lack activity against B. anthracis 1
- If meningitis is suspected, doxycycline may be suboptimal due to poor CNS penetration; consider alternative combinations 1
Transition to oral therapy when clinically stable: ciprofloxacin 500 mg twice daily OR doxycycline 100 mg twice daily 1
Total duration: 60 days (IV plus oral combined) due to potential spore persistence and reactivation risk 1
Adjunctive therapy: Consider corticosteroids for patients with extensive edema, respiratory compromise, or meningitis 1
Gastrointestinal Anthrax Treatment
Use the identical regimen as inhalational anthrax—this form carries similarly high mortality (25-60%) and requires aggressive multi-drug IV therapy 1
The same 60-day total duration applies, with transition to oral therapy when appropriate 1
Cutaneous Anthrax Treatment
Uncomplicated cutaneous disease:
- Adults: Ciprofloxacin 500 mg orally twice daily OR doxycycline 100 mg orally twice daily 1
- Children: Ciprofloxacin 10-15 mg/kg every 12 hours (max 1 g/day) OR doxycycline (weight-based dosing as above) 1
- Duration: 60 days (not the traditional 7-10 days) when bioterrorism or aerosol co-exposure is suspected 1
Complicated cutaneous disease requires IV multi-drug therapy when:
- Signs of systemic involvement are present 1
- Extensive edema develops 1
- Lesions involve the head and neck 1
In these cases, use the same IV multi-drug regimen as inhalational anthrax 1
Important note: Antimicrobial treatment renders lesions culture-negative within 24 hours, but eschar formation still progresses—this is expected and does not indicate treatment failure 1
Post-Exposure Prophylaxis
For confirmed or suspected aerosol exposure to B. anthracis:
- Adults (including pregnant and immunocompromised): Ciprofloxacin 500 mg orally twice daily OR doxycycline 100 mg orally twice daily 1
- Children: Ciprofloxacin 10-15 mg/kg every 12 hours (max 1 g/day) OR doxycycline (weight-based as above) 1
- Duration: 60 days 1
Switch to amoxicillin 80 mg/kg/day divided every 8 hours (max 500 mg three times daily) in children once penicillin susceptibility is confirmed, to minimize fluoroquinolone/tetracycline exposure 1
Critical principle: Base prophylaxis decisions on exposure circumstances, NOT on nasal swab results—negative nasal cultures do not rule out exposure 1
Special Population Considerations
Pregnant women: The high mortality from anthrax infection far exceeds any theoretical medication risks; use standard adult dosing without modification 1
Young children: Despite concerns about tetracycline effects on developing teeth and bones, the American Academy of Pediatrics supports doxycycline use for serious infections like anthrax 1
Immunocompromised patients: Use the same regimens as immunocompetent patients without dose adjustment 1