Stress Degradation Assessment of Lamotrigine Using a Validated Stability-Indicating HPTLC Method

In this work, a sensitive and stability-indicating HPTLC method for the determination of lamotrigine is presented. According to the International Conference on Harmonization guidelines Q1A, lamotrigine was exposed to a variety of stress conditions; these include heating in acidic, basic and neutral media. Its stability towards oxidative stress, humidity, high temperature and direct sunlight was also examined. Separation of the drug from its forced degradation impurities was achieved using TLC silica gel plates and a mobile phase composed of ethyl acetate: methanol: ammonia. The linear regression analysis of the data obtained for the correlation plots showed good linearity over the concentration range of 10-300 ng/spot. The forced degradation studies showed that lamotrigine is susceptible to degradation under acidic, basic, neutral and oxidative conditions, among which alkaline-induced hydrolysis had the highest degradative potential. Alternatively, the drug was stable under heat, humidity, and daylight stress factors. In order to assess the purity and stability of the drug in tablet formulations, the developed method was applied to the analysis of commercial tablets in brand and generic products. The obtained results showed that the degradation of the drug has not occurred in the marketed formulation that were analyzed by the described methodology.