Concomitant HPLC method for determination of lamotrigine, carbamazepine, and 10,11-carbamazepine epoxide in plasma using dual UV 240-220 nm wavelength detection

This paper presents a rapid, low cost, specific, high-performance liquid chromatographic (HPLC) method using an internal standard (pipamperone: PIP) for concomitant determination of lamotrigine (LMG), carbamazepine (CBZ), and its major metabolite, 10,11-carbamazepine epoxide (EPOCBZ). Drug detection is performed using a dual wavelength detection (200-240nm) to check the purity of chromatographic peaks. Mean retention times for LMG, EPOCBZ, PIP, CBZ were 3.73, 4.34, 5.41, and 7.93 minutes, respectively. Recovery ratios averaged 88.1% +/- 1.0 for LMG, 101.1% +/- 1.4 for CBZ, 101.0% +/- 1.6 for EPOCBZ, and 97.2% +/- 2.5 for PIP, respectively (n=6). In the range investigated, both the intra-day and the inter-day % relative standard deviation were less than 6.5% (n=6). Absorbance ratios of 240 versus 220 nm (AR 240/220 nm) averaged 0.401 +/- 0.0037 for LMG, 0.227 +/- 0.0046 for EPOCBZ, 0.525 +/- 0.0042 for CBZ, and 3.234 +/- 0.115 for PIP, respectively (n=4). Albeit, no interference was detected with any of the drugs (or metabolites) tested, which might be associated with LMG or CBZ; determination of AR 240/220nm is of interest in laboratory routine while minimizing the risk of possible interferences without additional cost and waste of time.