To the Editor.
—In a recent consensus report by Dr Wilson and colleagues1 on the current treatment of endocarditis in adults, recommendations regarding dosing and pharmacokinetic monitoring of vancomycin hydrochloride warrants clarification and reevaluation. Development of the so-called therapeutic range for vancomycin resulted from the perceived relationship between drug concentration and toxicity. Potential ototoxicity and nephrotoxicity in relation to specific levels of vancomycin have not withstood vigorous challenges to their validity.2 Similar to β-lactams, vancomycin exerts its bactericidal actions by inhibiting bacterial cell wall synthesis, a process that is relatively independent of concentration. Consequently, drug concentrations exceeding four to five times the minimum inhibitory concentration (MIC) are not necessary; instead, maintaining drug concentrations above the MIC of the organism for the entire dosing interval is desired. The current recommendation by Wilson and colleagues requires therapeutic vancomycin peak concentrations of 30 to 45 μg/mL for twice-daily dosing. In clinical
Johns TE, Iafrate P, Sproat TT, Palmer S. Antibiotic Treatment for Infective Endocarditis. JAMA. 1996;275(12):911. doi:10.1001/jama.1996.03530360021028