Development of Stability Indication Assay Method and Degradation Studies of Selected Drugs Targeting Cardiovascular and Kidney Disorders

Abstract

Stability testing of pharmaceutical products is important to assure their stability and efficacy throughout the shelf life. It is a mandatory requirement by various regulatory agencies across the globe. In the first part of the study, accelerated stability studies of Levosimendan (LEV) were performed as per ICH Q1A (R2) guideline. Under accelerated stability conditions (40°C/75%RH), two unknown degradation impurities were found at a level of 0.05-0.15% by the HPLC analysis. Further, these impurities synthesized in a larger quantity and isolated from the crude sample using preparative chromatography. The structure of isolated impurities were characterized using various spectrometric and spectrophotometric methods including LCMS/ MS, NMR (1H, 13C, COSY, HMBC, and HSQC) and FTIR. Based upon the results, the structure of impurities were proposed as (2Z)-2-cyano-2-(2-{4-[(4S)-4-methyl-6-oxo-1, 4, 5, 6- tetrahydropyridazin-3-yl] phenyl} hydrazinylidene) ethanamide (DP1) and (5S)-5-Methyl-6- phenyl-4,5-dihyropyridazin-3(2H)-one (DP2). The origin of the impurities was also postulated by proposing the plausible mechanism of formation. In second part of thesis, solid state degradation study was carried out on Mirabegron (MIR) in its various forms i.e. amorphous, crystalline and equal ratio of both forms. All were subjected to 25°C/65% RH, 40°C/75% RH, 50°C/90% RH and 60°C/0% RH conditions along with and without solid stressors with open and closed conditions for different time interval. Also, liquid state degradation was carried out under acidic conditions to understand the degradation behavior of drug. The samples were analyzed by using HPLC and their degradation profile were compared to understand degradation behavior of drug under in its different forms. The formed degradation products were characterized using LC-MS analysis. Two degradation products were isolated using conventional column chromatography having purity of more than 95%. The isolated DP1 converted to DP2 upon storage due to its thermolabile nature. Further, the plausible mechanism of formation of impurities was postulated. In the next part of the thesis, a stability indicating method was developed for Sacubitril/Valsartan (SAC/VAL) complex using UHPLC in presence of their seven related impurities and degradation products. The developed method was validated as per ICH Q2 (R1) guideline and all the validation parameters were found within the acceptance criteria. Further, forced degradation study of SAC/VAL was carried out and the results indicated that the drugs were prone to acidic, alkaline, neutral hydrolytic conditions and oxidative stress conditions. The newly developed method can be used for estimation of assay and related substances from bulk drug and their finished formulations with good efficiency.