Degradation processes quite often involve free radicals and transition metals that are responsible for most of the damage that occurs in drug products. By analyzing an EPR signal, one can identify, quantify and monitor time behavior of the free radicals involved in product degradation.
Forced degradation (stress testing) is routinely used in pharmaceutical development to predict the stability of drug products that affects purity, potency, and safety. EPR can successfully detect and monitor short-lived free radicals produced during stress testing via chemical, thermal, or photochemical reactions. EPR can also determine radical scavenging effectiveness and efficiency of antioxidants.
Chemistries involving radicals, transition metals and other unpaired electron species are integral components of maximizing product yield and minimizing the environmental footprint of synthetic reactions. Reaction monitoring is critical for process understanding, optimization and scaling up, leading to cost savings and ensuring the quality of the final product. The quantitative and non-intrusive nature of EPR makes the technique extremely powerful for the identification and characterization of radical and transition metal reaction intermediates, providing insights into the mechanisms and kinetics of chemical reactions.
Sterilization of pharmaceuticals often generates free radicals that are responsible for degradation and drug potency decrease, toxicity of the sterilized materials, etc. EPR can determine stability of drug products after sterilization, characterize the free radicals and identify their source.
Identification, quantification, and control of impurities in APIs and formulation products are critical in drug development. EPR can detect and identify traces of transition metals and monitor degradation processes that involve free radicals, transition metal catalysts, and other impurities.