Plasma beta 2 microglobulin as a means of predicting gentamicin serum concentrations

A novel and accurate method for predicting gentamicin peak serum concentration is described. The method considers body weight and renal function as determined by the concentration of beta 2 microglobulin in plasma. In 32 subjects whose renal function ranged from normal to severely impaired, the peak serum concentration of gentamicin was more closely correlated with beta 2 microglobulin (r = 0.69) and with creatinine clearance (r = 0.69) than with serum creatinine (r = 0.53). A nomogram was constructed which related plasma beta 2 microglobulin concentrations and body weight to predicted gentamicin peak serum concentrations. When the nomogram was clinically applied, the predicted peak gentamicin concentrations corresponded closely to the actual measurements obtained (t = 0.64; P is not significant). We suggest that plasma beta 2 microglobulin concentrations compare favorably with serum creatinine values in the prediction of gentamicin peak concentrations in patients with renal impairment.