Changes in the serum protein binding of vancomycin in patients with methicillin-resistant Staphylococcus aureus infection: the role of serum alpha 1-acid glycoprotein levels.

The relationship between albumin or alpha 1-acid glycoprotein (AAG) levels and vancomycin (VCM) protein binding was studied in 44 serum samples from the 10 patients with methicillin-resistant Staphylococcus aureus (MRSA) infection receiving VCM therapy. Eighty serum samples from 80 healthy subjects were used as a control for albumin and AAG levels. The protein binding percentage of VCM in the serum of the patients varied widely from 27 to 62%. The mean albumin level (34 g/L) was significantly lower than that in healthy subjects (46 g/L). There was no correlation between the binding percentage and serum albumin level in the patients (r = -0.25, p > 0.1). The mean AAG level in the patients (1.51 g/L) was significantly higher than in healthy subjects (0.59 g/L). There was a significant correlation between the binding percentage of VCM and serum AAG level (r = 0.63, p < 0.001). The binding percentage of VCM individual patients changed in parallel to serum AAG and C-reactive protein (CRP) levels, which is a useful marker of acute phase response. There were also significant correlations between AAG, albumin, and CRP levels. The present results indicate that the increased AAG level in serum of the patients appeared to have a significant effect on the protein-binding characteristics of VCM.