Development and validation of a method for phenobarbital in serum: anticonvulsant pharmacotherapy monitoring

The therapeutic drug monitoring (TDM) is an important strategy for the effectiveness and safety of long-term pharmacotherapy, such as the use of phenobarbital as an anticonvulsant drug in epilepsy. In this sense, HLPC has been presented as a technique for the measurement of phenobarbital in serum. However, the ideal conditions for carrying out the method must be established for each laboratory reality. An analytical method using HPLC was developed and validated in order to identify and quantify Phenobarbital in blood. The chromatographic conditions were C-18 column (Shimpack XR-ODS 50L x 3.0), acetonitrile-water mobile phase (30:70, v v-1), 0.2 mL min-1 flow and reading wavelength of 210 nm. Linearity was established in the range of 2.5 to 80 μg mL-1, the linear correlation coefficient was 0.9981. The average of the coefficient of variation of the precision was 5.30%. The relative standard error of the accuracy was -2.17% and of the recovery coefficient was 97.83%. In all eleven patients, phenobarbital concentrations were below the therapeutic range. The tested method was selective, linear, precise, accurate and showed good recovery.