Solubility Enhancement and Pharmacokinetic Assessment of Chemically Modified Lamotrigine in Rat Blood Plasma by HPLC
Authors: R. Gupta Krishna , R. Gautam Ashok , V. Ganorkar Anvesha , J. Umekar Milind 
Published: October 2019

Aims:

Synthesis/preparation of Lamotrigine (LMN) complexes with β-CD, Caffeine, Nicotinamide, EDTA and

Development of a new reverse phase liquid chromatographic (HPLC) method for the investigation of Lamotrigine in rat plasma after oral administration and pharmacokinetic assessment of Lamotrigine.

Study Design: The present work describes the formation of LMN drug complexes with β-Cyclodextrin, Caffeine, Nicotinamide and Disodium EDTA. Physical mixture, kneading and solvent evaporation methods were used to prepare LMN complexes (In ratios 1:1, 1:2, 2:1). Further characterization was performed by UV, FTIR, PXRD, and DSC. A reverse phase HPLC method was developed for the investigation of LMN in rat plasma using internal standardization method after oral administration of LMN and its complexes.

Place and Duration of Study: Department of Pharmaceutical Chemistry, Smt. Kishoritai Bhoyar College of Pharmacy, RTMN University, Nagpur, between July 2018 and June 2019.

Methodology: LMN complexes with β-CD, Caffeine, Nicotinamide, EDTA was prepared in three ratios i.e. 1:1, 1:2 and 2:1 and characterized by UV, FTIR, PXRD, and DSC. In-vitro Solubility study was performed by saturation solubility study, further % practical yield, drug content, melting point was determined. In-vitro dissolution study of prepared complexes was performed in dissolution apparatus using the paddle method, according to USP Type II. Dissolution studies were carried out using 900 mL 0.1M HCl at 37± 0.5°C at 50 revmin−1 (US FDA guidelines).The interaction of LMN with these hydrophilic complexing agents was characterized by UV, FTIR, PXRD and DSC.

A reverse phase HPLC bioanalytical method was developed and validated as per ICH guidelines for the quantitative determination of LMN in rat plasma using internal standardization method (HTZ) after oral administration of LMN and its complexes. The method was successfully applied for the pharmacokinetic study in rat. The pharmacokinetic parameter like AUCt, AUCi, MRTi, Cmax, Tmax, t1/2, were calculated using pharmacokinetic software PK solver 2. The efficient separation was carried out for High Performance Liquid Chromatography (HPLC) method on Eclipse XDB-C18 (150×4.6×5 µ) column using a mobile phase consisting of filtered and degassed mixture of potassium dihydrogen orthophosphate buffer (pH 7.0) and Methanol in the ratio 65:35 v/v at a flow rate of 0.8 mL/min and UV detection at 307 nm.

Results: The LMN complexes were successfully prepared and characterized by UV, FTIR, PXRD, and DSC from which solvent evaporation method was found to be best as per result of in-vitro dissolution study. In-vitro dissolution study reveals that LMN-Caffeine (C1) and LMN-NTM (N1) complexes showed 100.14 and 100.01% drug release at 15 min and 20 min respectively as compared to pure drug (LMN) which shows only 50.56% drug release at 75 min.

LMN concentration in blood plasma reached (Cmax) was found to be 19.4732 µg/mL at Tmax of 5h, Whereas Cmax of LMN complexes were found to be 48.4876 (B1), 72.2160 (C1), 62.2739 (N1) and 49.3170 (E1) µg/mL at Tmax of 5h out of which complex C1 and N1 in the present study resulted in a sharp increase in Cmax. All complexes showed 4 to 5 time enhancement of Cmax as compared to LMN.. The results demonstrated that complexes of Lamotrigine were successful strategy to improve the solubility and dissolution behavior of Lamotrigine. The complex B1 shows maximum t1/2 and MRTi of 36.224 h and 52.441 h as compared to C1, N1 and E1 having t1/2 of 14.1575, 16.258 and 21.702 h and MRTi  of 19.997, 22.994 and 30.883 h respectively. Hence B1 required lesser dosing frequency as compared to other complexes.

Conclusion: The Lamotrigine complexes were prepared and confirmation of prepared complexes was done by physical characterization (FTIR. DSC, PXRD and UV) and solubility determination by saturation solubility study. The bioanalytical method was developed for estimation of plasma drug concentration of LMN. The method was validated according to ICH guidelines to estimate the mean plasma concentration of LMN after oral administration using internal standardization method (HTZ). Method was reproducible and high recovery of LMN from its complexes was achieved. The method was found to be highly satisfactory sensitive, accurate, linear and specific.