A patient is prescribed moxifloxacin for community-acquired pneumonia. Moxifloxacin should NOT be used for urinary tract infections primarily because:

• A It has poor oral bioavailability and cannot achieve systemic blood levels
• B It lacks activity against Enterobacteriaceae commonly causing UTIs
• C It causes crystalluria at urine pH values typical of UTI patients
• D It is predominantly eliminated by hepatic metabolism and biliary excretion, achieving subtherapeutic urinary concentrations ✓

Explanation

Moxifloxacin undergoes extensive hepatic glucuronidation and sulfation, with only about 20% excreted unchanged in urine, making urinary drug concentrations insufficient for treating UTIs. Ciprofloxacin and levofloxacin, which are predominantly renally cleared with high urinary concentrations, are preferred for UTIs. Moxifloxacin has good gram-negative activity including many Enterobacteriaceae; its oral bioavailability is excellent (~90%); crystalluria is not a significant concern with fluoroquinolones.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.