Detection of vancomycin levels in patients receiving telavancin but not vancomycin

Abstract

Sir, Telavancin is a lipoglycopeptide antibiotic with a chemical structure closely related to the glycopeptide antibiotic vancomycin. Telavancin has excellent in vitro activity against methicillinresistant staphylococci and, in the trials which led to its approval for the treatment of skin and soft tissue infections, it was shown to be non-inferior to vancomycin. 1 Renal toxicity is the principal significant adverse effect of telavancin. 2 A standard dose of 10 mg/kg daily is recommended in patients with normal renal function and monitoring of serum or plasma levels is neither recommended nor available commercially. 2 It is not known if telavancin serum levels correlate with the efficacy or renal toxicity of this antibiotic. Perhaps due to a lack of therapeutic superiority data and concerns about renal toxicity, telavancin has yet to be widely used in clinical practice. Recently, a patient receiving the standard dose of telavancin for a staphylococcal infection was demonstrated to have an apparent detectable serum vancomycin level (after the level was inadvertently ordered by a house officer). This serendipitous finding led us to check vancomycin levels in several other patients with normal renal function who were receiving standard doses of telavancin. No patients had received vancomycin. Trough levels were obtained immediately prior to a dose of telavancin and peak levels were obtained 1 h after the infusion was completed. The vancomycin serum levels were determined by a particle-enhanced turbidometric inhibition immunoassay method (Synchron LX System, Beckman Coulter, Inc., Brea, CA, USA). The results are shown in Table 1. Wespeculatethatif aconsistent correlationcanbeestablished between serum vancomycin and telavancin levels in patients treated with telavancin, a commercially available vancomycin serum level assay can then be used to monitor telavancin therapy, in place of an unavailable telavancin assay, in order to establish possible correlation between telavancin levels and its clinical efficacy and/or renal toxicity. Although telavancin plasma assays were apparently done as part of approval studies, we had no access to a telavancin assay to attempt to establish the correlation. 3 If the manufacturer of telavancin or an independent investigator is able to perform telavancin assays, they may choose to perform such a study.