Factors affecting the stability of drugs and their metabolites in biological matrices

Measuring the drug and its metabolite in the biological sample provides a fundamental relationship between the dose administered and superior clinical efficacy. Hence, during analytical method development and validation, the drug concentration at the time of analysis and sample acquisition must be identical. The drugs and their metabolites might undergo degradation in acquired samples due to physical and chemical reactions, which results in the underestimation of the drug quantity in the original sample. Therefore understanding the factors influencing the stability of the drug and their metabolites, both in vitro and in vivo play a critical role in the bioanalysis and estimation of the drug pharmacokinetics. This chapter demonstrates different in vitro and in vivo factors that influence the drug and metabolite stability in the acquired biological sample with relevant examples.