In penicillin-allergic patients with anaerobic odontogenic infections, which antibiotic is preferred?

• A. Azithromycin
• B. Clindamycin
• C. Amoxicillin
• D. Metronidazole

Answer: (B)

In dental infections that are anaerobic and mixed in nature, you want an antibiotic with strong anaerobic coverage that doesn’t involve a beta-lactam. The oral flora in odontogenic infections includes anaerobes such as Peptostreptococcus, Prevotella, and Fusobacterium, along with facultative bacteria. Clindamycin provides reliable coverage against anaerobes and many gram-positive cocci, and it penetrates bone and abscesses well, which is ideal for dental infections. It’s also a common choice for patients with penicillin allergy because it avoids beta-lactam exposure while still treating the typical organisms involved.

Azithromycin has limited anaerobic activity, amoxicillin is a penicillin and should be avoided in allergy, and metronidazole covers anaerobes but doesn’t adequately cover the facultative streptococci common in these infections unless paired with another agent. Hence, clindamycin is preferred as a single-agent therapy in penicillin-allergic patients with anaerobic odontogenic infections.