**3.1 Chemical reactions that cause drug degradation**

Many drugs are derivatives of carboxylic acid or contain functional groups based on this moiety, for example esters, amides, lactones, lactams, imides or carbamates [5]. Accordingly, various chemical reactions can result in the degradation of the drug. These reactions include hydrolysis, oxidation, photochemical reactions, polymerization, isomerization, racemization and dehydration [4, 5, 8].
