Determination of impurities of montelukast which is used in asthma therapy and in vitro evaluation of their probable genotoxic effects

During manufacturing and storage of drugs that include montelukast used chronically in asthma theraphy, various impurities can form. Impurities affect safety, efficacy, quality of drugs, particularly when they pose genotoxic effects, causing serious health problems. Current study aims analysis of montelukast impurities and toxicological assessment via considering the regulatory approaches regarding control of impurities. Quantitation of impurities (sulfoxide, cis-isomer, Michael adducts I&II, methylketone, methylstyrene), already indicated in USP was conducted using RP-HPLC analysis on pediatric and adult drug products on market. Validation of analytical method was conducted according to ICH guideline. For sulfoxide impurity that was above qualification limits, having no report of toxicity data, prediction analysis in in silico QSAR method, bacterial gene mutation test in S.typhimurium TA98, TA100, TA1535, TA1537, E.coli wp2[pKM101] and wp2uvrA were performed. The cytotoxicity and genotoxicity assessment was investigated respectively by determining mitotic index and using in vitro chromosomal aberration (CA) test. Impurities except sulfoxide were under qualification limits in the analysis of different batches of 20 products at 4 mg/10 mg doses for 11 companies. The sulfoxide exceeds limits in 2 companies for pediatric chewable tablets and in 7 companies for adult tablets. Sulfoxide impurity was not mutagenic in Leadscope QSAR analysis and bacterial gene mutation assay (Ames MPF Penta I) w/wo metabolic activation system. Sulfoxide impurity was dose-dependent cytotoxic in human peripheral lymphocytes w/wo metabolic activation system, however, it was nongenotoxic in CA test. Results have shown sulfoxide impurity as nonmutagenic/nongenotoxic and to be classified as an ordinary impurity according to guidelines. Keywords: genotoxic impurities, QSAR analysis, Ames test,chromosomal aberration test, hplc, regulations