Muscle pain associated with daptomycin

Objective: To report a case of muscle pain without pronounced creatine kinase (CK) elevation in a patient receiving daptomycin. Case Summary: A 26-year-old African American woman had antibiotic intolerance to vancomycin and quinupristin/dalfopristin. She presented with methicillin-resistant Staphylococcus aureus endocarditis that was treated with intravenous daptomycin 6 mg/kg daily for 14 days. The patient developed muscle aches and pains with only a minor elevation (492 U/L) of CK; both resolved after daptomycin was discontinued. Discussion: Daptomycin is a newly approved lipopeptide antibiotic derived from Streptomyces roseosporus with rapid bactericidal activity. Daptomycin has excellent coverage against gram-positive bacteria. The adverse effect profile has included rare reports of myopathy and elevated CK levels. Daptomycin is a promising agent with many potential applications. Once-daily dosing has diminished the preclinical incidence of myopathy. The current package labeling recommends discontinuation of daptomycin with significant myopathy symptoms in association with a CK elevation >1000 U/L or in patients without muscle pain and a CK >10 times normal. Conclusions: An objective causality assessment revealed that the myopathy was possibly related to daptomycin. Clinicians should recognize that significant myopathy with daptomycin can occur without pronounced CK elevation.