Daptomycin is considered for a patient with MRSA bacteremia and concurrent hospital-acquired pneumonia. Why is daptomycin inappropriate for the pulmonary component?
- A It cannot achieve adequate penetration across the blood-brain barrier
- B It is a substrate for efflux pumps upregulated in lung tissue
- C It is extensively bound by pulmonary surfactant, rendering it inactive in alveolar lining fluid ✓
- D It is rapidly degraded by pulmonary carboxylesterases
Correct answer: C. It is extensively bound by pulmonary surfactant, rendering it inactive in alveolar lining fluid
Explanation
Daptomycin is a cyclic lipopeptide that disrupts bacterial membrane potential in a calcium-dependent manner, but it binds avidly to pulmonary surfactant, which neutralizes its activity in the alveoli, so it must not be used for pneumonia despite excellent MRSA blood activity. It penetrates well into most tissues, and efflux pumping or enzymatic degradation play no role in this failure mode.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.