A 70-year-old man with stage 4 chronic kidney disease needs therapy for community-acquired pneumonia caused by Chlamydia pneumoniae. Which statement about tetracycline selection in this patient is correct?
- A Doxycycline requires dose reduction proportional to creatinine clearance, unlike tetracycline
- B Both doxycycline and tetracycline accumulate dangerously in renal failure and must be avoided
- C Doxycycline may be used without dosage adjustment because non-renal elimination compensates for reduced renal clearance ✓
- D Minocycline is preferred because it is exclusively renally cleared
Correct answer: C. Doxycycline may be used without dosage adjustment because non-renal elimination compensates for reduced renal clearance
Explanation
Doxycycline is unusual among tetracyclines because much of its elimination is faecal and non-renal, so no dosage adjustment is needed even in advanced renal failure. Older tetracyclines such as tetracycline itself accumulate in renal impairment and worsen uraemia by their antianabolic effect, so they are contraindicated. Minocycline is hepatically cleared but offers no advantage here.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
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