Appropriate Use of Vancomycin Hydrochloride in Elderly Patients with Methicillin-Resistant Staphylococcus aureus (MRSA) Infections

Objectives: A dose of vancomycin should be reduced for treatment of methicillinresistant Staphylococcus aureus (MRSA) infections in elderly patients with decreased renal function to avoid nephrotoxicity and ototoxicity. By adjusting doses and dosing intervals with therapeutic drug monitoring (TDM), we studied the most appropriate use of vancomycin in 6 elderly patients with MRSA infections.Method: The dosage-regimen was as follows: Vancomycin was abministered intravenously over 60 min at a dose of 0.5 g, b.i.d. in all patients. The same dosage-regimen was maintained when the trough vancomycin concentration was less than 10 μg/ml on the 3rd day with TDM. If the trough concentration was≥10μg/ml, 0.5 g of vancomycin was given once daily. Three days after a change of dosing interval, the dose of vancomycin was reduced to 0.25 g if the trough concentration was≥10μg/ml with TDM, otherwise the second dosage-regimen was maintained. The primary endpoint was disappearance of MRSA and the second was improvement of clinical findings (CRP, body temperature, white cell count).Results: MRSA disappeared in all patients. Adjustment of the dosage-regimen was made in 4 out of 6 patients through the treatment. The global improvement rating was 83.3% in this study. Adverse events included the mild increase of serum GOT, GPT and ALP in only one patient. The values of these enzymes returned to normal range after cessation of the antibiotic without additional medical treatment.Conclusion: We recommend a dosage-regimen of vancomycin of 0.5 g, b.i.d. at the start of treatment of MRSA infections in elderly patients. TDM should be performed after steady-state vancomycin concentration is reached (usually 3 days after the start of treatment) in order to assure efficacy and safety of the antibiotic. Patients with decreased renal function (CLCR≤40 ml/min) should be treated with a much lower dose or a longer interval from the start of treatment, and TDM is strongly recommended for those patients.