A recent meta-analysis has shown that the serum cystatin-C concentration is a superior marker to serum creatinine for estimating the glomerular filtration rate (GFR).In this study,we investigated the relationship between serum vancomycin (VCM) and cystatin-C concentrations to establish a simple method of setting initial doses for VCM therapy.
We conducted a non-parametric analysis in which data from 140 patients treated with VCM for Methicillin-resistant Staphylococcus aureus (MRSA) infection were divided into 2 groups (a once-a-day group (n=54)and a twice-a-day group (n=86)).The GFR was estimated using the equation of Hoek based on the serum cystatin-C concentration.
In the once-a-day group,VCM dose/serum VCM trough concentration (D/C) ratios were significantly different among 4 -subgroups established on the basis of GFR.The subgroups were GFR<20,20-40,40-50 and 50>mL/min and the average D/C ratios in them were 28.4,57.2,87.9 and 170.3,respectively.In the twice-a-day group,D/C ratios varied signifi-cantly among 3 subgroups based on GFR,which were GFR<50,50-80 and >80 mL/min,and the average D/C ratios in them were 75.0,149.9 and 264.0,respectively.
Based on these findings,we simply established the following initial dosage regimens for VCM using GFRs estimated from serum cystatin-C concentrations : 500 mg q.o.d for GFR<20,500 mg s.i.d for GFR of 20-40,1000 mg s.i.d for GFR -of 40-50,1500 mg b.i.d for GFR of 50-80 and 2000 mg b.i.d for GFR>80.In conclusion,we consider that serum cystatin-C concentrations are a useful basis for setting initial doses of VCM,in particular for patients with a GFR<80.
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