Analytical aspects of the stabilization of drugs in pharmaceutical formulations.

: The selection of a suitable procedure for stabilizing a drug in various pharmaceutical formulations requires highly specific and accurate analytical methods. In this paper the general problems associated with the specificity of the selected analytical methods (spectrophotometry, HPLC etc.) are discussed through the examples of phenyl-alkylamine and phenothiazine drugs. Studying the influence of different antioxidants on the rate of decomposition and detecting simultaneously the decomposition products, radicals and intact active ingredients enabled a better understanding of the degradation mechanism. The impurity profile (different decomposition products in the mixture) was found to be the function of the type and concentration of the stabilizers. A kinetic study demonstrated on phenylalkylamine type drugs using selective analytical methods clarified the mechanism of stabilizer action and allowed the perfect description of the degradation pathway.