[Initial dosage of vancomycin in neutropenic hematologic patients]

To evaluate the percentage of neutropenic patients who reach the therapeutic threshold when vancomycin is given at standard initial doses of 500 mg/6 hr, and to assess the creatinine clearance and body vancomycin clearance in such patients.

The study was performed on 37 haematological patients with normal renal function. They received intravenous vancomycin at an initial 500 mg/6 hr doses. The plasma concentration of the drug was assessed 48-72 hr later, pharmacokinetic parameters being calculated. Creatinine clearance was estimated by two different methods.

The concentration attained was beyond the therapeutic threshold in 100% of the patients. The correlations between vancomycin and creatinine clearance were r = 0.42 and r = 0.47 when the Cockroft-Gault's and the Jellife's methods, respectively, were used. Administration of vancomycin at initial doses of 500 mg/6 hr renders a very high percentage of patients with plasma concentration of the drug beyond the therapeutic margin.

1) The poor correlation between creatinine and vancomycin clearance in the patients with normal renal function does not allow using nomograms based on such values for estimation of the initial doses. 2) The estimation of initial doses based on the patient's weight (20-25 mg/kg) may render a higher percentage of patients with therapeutic concentrations from the beginning of treatment. The maintenance doses can be adjusted at 48-72 hr, after measuring the plasma concentrations. 3) Therefore, it seems advisable to perform further clinical assays on different groups in order to verify an increase of the drug's efficacy with no higher toxicity when the initial vancomycin doses is adjusted according to the patient's weight, as recommended here.