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Interpretive Handbook

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Test 81592 :
Vancomycin, Trough, Serum

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Vancomycin is an antibiotic used to treat infections caused by gram-positive organisms that are resistant to beta-lactam antibiotics, such as methicillin-resistant staphylococci (MRSA), Staphylococcus viridans group, penicillin/cephalosporin-resistant Streptococcus pneumoniae, and penicillin/ampicillin-resistant Enterococcus species.

 

The oral formulation, which is not absorbed, is used in the treatment of pseudomembranous colitis caused by Clostridium difficile. Vancomycin is also used when patients are intolerant or allergic to beta lactams.

 

Vancomycin has been associated with nephrotoxicity and ototoxicity, although it appears that many of these reports reflected impurities in early formulations. Monitoring of vancomycin-related nephrotoxicity is recommended only for patients with reduced renal function, those receiving aggressive or prolonged vancomycin regimens, or those at high risk including patients co-medicated with other nephrotoxic agents.

 

Trough concentrations are recommended for therapeutic monitoring of vancomycin, preferably acquired at steady-state (just before fourth dose). To avoid development of resistance, vancomycin trough levels should remain >10 mcg/mL. Complicated infections require higher target levels, typically 15 to 20 mcg/mL. Peak concentrations do not correlate well to efficacy or nephrotoxicity, but may be useful for pharmacokinetic analyses (eg, area under the curve [AUC]studies) or for select patients.

Useful For Suggests clinical disorders or settings where the test may be helpful

Trough concentrations drawn at steady-state are the preferred test for monitoring vancomycin therapy.

Interpretation Provides information to assist in interpretation of the test results

Trough levels correlate better with efficacy than peak levels, with target trough levels of 10 to 20 mcg/mL, depending on the type of infection.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

No significant cautionary statements

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Therapeutic concentration: 10.0-20.0 mcg/mL

Complicated infections: 15.0-20.0 mcg/mL

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Rybak M, Lomaestro B, Rotschafer JC, et al: Therapeutic drug monitoring of vancomycin in adult patients: A consensus review of the American Society of Health-System Pharmacists, the Infectious Diseases Society of America, and the Society of Infectious Diseases Pharmacists. Am J Health Syst Pharm 2009;66:82-98

2. Estes L, Wilson J: Mayo Guide to Antimicrobial Therapy, Mayo Clinic, 2005-2008


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