What is a first-line antibiotic option for post-exposure prophylaxis of inhalational anthrax?

• A. Penicillin G
• B. Ciprofloxacin or doxycycline (typically for 60 days)
• C. Amoxicillin
• D. Azithromycin

Answer: (B)

Post-exposure prophylaxis after inhalational anthrax aims to prevent any spores that may germinate into active infection. The best first-line choice is a fluoroquinolone or a tetracycline, specifically ciprofloxacin or doxycycline, given for about 60 days. This long course covers the entire window during which inhaled spores can germinate and cause disease, ensuring ongoing suppression of bacterial growth. These agents have strong activity against Bacillus anthracis, are effective when taken orally, and support practical, large-scale prophylaxis in a public health setting. Penicillin G, while active against anthrax, is not preferred for first-line PEP due to the need for intravenous administration and other practical considerations. Amoxicillin and azithromycin are not the standard first-line options for inhalational exposure, though they may be considered in certain circumstances (for example, penicillin allergy) as alternatives.