2.2.7. Stability studies for optimum LZ nanoemulsion and solid nanoemulsion formulations

Three batches of both nanoemulsion and SNE were taken separately and subjected to the different temperatures of 30, 40, 50, and 60 °C for 90 d at constant humidity. At specific time intervals, samples of each patch were taken to assess the LZ content using a UV spectrophotometer study at a lambda max of 240 nm. The amount of drug that remains and that decomposed through time was calculated. The LZ degradation order was determined graphically and for each temperature, degradation rate constant ‘K’ was obtained. To determine the shelf life of the optimum nanoemulsion and SNE formulations, an Arrhenius plot was drawn between K and 1/T. From this plot, the rate constant at room temperature ‘K₂₅′ was obtained. The shelf life of each optimum formulation was calculated according to the following equation (Alam et al., 2012, Krishna et al., 2013, Mohima et al., 2015, Ali and Hussein, 2017a, Ali and Hussein, 2017b):