Continuous perineural infusions of bupivacaine for prolonged analgesia--a rapid two-point method for estimating individual pharmacokinetic parameters.
Results of previous studies have shown a 5-10 fold range in the clearance total and half-life of bupivacaine. Since bupivacaine has a narrow therapeutic range and highly variable pharmacokinetic parameters, rapid estimation of the parameters allows early dosage regimen adjustments, and hence, better pain management. The pharmacokinetic parameters in 17 patients were estimated based on two samples drawn within 18 h after initiation of therapy. Based on the estimated parameters, a later sample's concentration was predicted. Results of this study confirm the previously reported large variation in pharmacokinetic parameters. An excellent agreement between actual and predicted concentration was found. The use of this method allows early readjustment in the dosage regimen, resulting in effective pain management without compromising patient safety.