The main objective of carrying out stability studies of the drug product is to establish shelf life of drug during storage. Stability of drug is defined as “The capability of a particular formulation in a specific container/closed system, to remain within its physical, chemical, microbiological, therapeutic, and toxicological specifications throughout its shelf life”. As mentioned in the International Conference on Harmonization (ICH) guideline Q1A (R2), stability studies are commonly the activity on the critical path to regulatory filing and approval. Stability studies are of different types and different methods are useful for the determination of stability like real-time stability testing, accelerated stability testing, retained sample stability testing and cyclic temperature stress testing. pH and temperature are the main factors influencing the stability of the drug. The pH-rate profile (log(k)vs pH) is the pH dependence of the specific rate constant of degradation of compounds. Forced degradation includes deterioration of new drug substances and products at more severe conditions than the accelerated conditions and it indicates the accuracy of stability-indicating methods. The different conditions applied during the forced degradation include hydrolytic, oxidation, photolytic and thermal stress etc. The techniques utilized for evaluation of stability studies can be LC-MS/MS, HPLC-DAD, HPLC-MS, HPLC-UV, HPTLC, TLC, LC-NMR etc. amongst them some techniques shows high sensitivity and resolution power to establish more effective stability-indicating method while for shelf life estimation of drugs and products the different methods mentioned are FDA’s method, the direct method, inverse method, simulation results and Garret and Carper method. Thus stability testing of pharmaceutical products inputs specific scheme in the evolution of a new drug as well as new formulation.

Aim: The current study dealt with the degradation behavior of Bilastine and degradation kinetics of a drug in solution state. Background:  Very limited information on the effect of pH on maximum stability has been published. In order to understand the degradation kinetics of bilastine, aqueous stability studies were carried out, because such studies on bilastine have not been reported in the literature, further no methods have reported about shelf-life determination of bilastine. The study design involves selection of stability indicating RP-HPLC method for estimation of drug then evaluation of degradation kinetics, shelf-life determination and validation of proposed method. Results: The Shimadzu HPLC series 1100 was used for stress degradation analysis of bilastine in tablet dosage form. The analysis was performed using Agilent ZORBAX SB-C8 (4.6×150×5µm) column and Phosphate Buffer: Acetonitrile (pH-5.0) in the ratio of 60:40 as mobile phase; wavelength selected for analysis was 254nm with the flow rate of 1mL/min at which drug showed sharp peak. The analysis was performed on the isocratic pump mode with the injection volume of 20µl. The mobile phase is used as diluent. The proposed method was found to be linear over the range 10 to 50 µg/mL. The analysis was performed by placing standard and samples with 7 different pH buffer, oxidative and neutral hydrolytic solutions in oven at 40ºC, 60⁰C and room temperature for an interval of 30, 60, 90, 120, 150, 180 mints for standard and samples. The results indicated that the pH, temperature, ionic strength and oxidation greatly influence the stability of Bilastine and the degradation behavior of Bilastine followed pseudo-first-order kinetics. Bilastine was most stable in neutral, alkaline, lower temperature conditions and lower ionic strength. Conclusion: The proposed method was found to be specific, selective and robust and successfully applied for its assay, degradation (stress testing) of drug and degradation kinetics in solution state. Keywords: Degradation, Stability, Bilastine, RP-HPLC, Kinetics