Simultaneous liquid-chromatographic determination of carbamazepine and its epoxide metabolite in plasma.

We describe a liquid-chromatographic method for the simultaneous quantification of carbamazepine and its 10,11-epoxide metabolite in plasma. The method is used routinely in the analysis of carbamazepine and its epoxide in 0.5 mL of plasma at concentrations of 1 to 20 and 0.2 to 5 mg/L, respectively. The use of peak-height ratios as a measure of detector response appeared to provide better precision and accuracy than peak-area ratios.