A 6-year-old boy presents with fever, headache, and an eschar in a scrub-endemic area. Scrub typhus (Orientia tsutsugamushi) is suspected. Which tetracycline is the drug of choice, and why is doxycycline preferred in children over older tetracyclines despite the class warning?
- A Doxycycline; it binds less to calcium and causes less tooth discoloration than older tetracyclines ✓
- B Minocycline; it does not bind to developing teeth
- C Tetracycline; it is the only tetracycline safe under 8 years
- D Tigecycline; it is not chelated by calcium
Correct answer: A. Doxycycline; it binds less to calcium and causes less tooth discoloration than older tetracyclines
Explanation
Doxycycline is first-line for scrub typhus and Rocky Mountain spotted fever. Unlike older tetracyclines (tetracycline, chlortetracycline), doxycycline has lower calcium-binding affinity, causing significantly less tooth discoloration. For courses under 21 days, the FDA and IAP consider doxycycline acceptable in children under 8 years when benefits outweigh risks. Option B is wrong because minocycline is not first-line and also deposits in teeth.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.