Quantitative Determination of Drugs in Dosage Forms as a Tool of Quality Control Studies

Pharmaceutical stability may be defined as the capability of a particular formulation, in a specific container/closure system, to remain within its physical, chemical, microbiological, therapeutic, and toxicological specifications, during transport, storage and use. Chemical degradation may results in a loss of potency or an increase in drugs toxicity, so that clinical use of a medicine must be unacceptable if the degradation is relatively great. When a drug dosage form is altered (by dissolution, pulverization, or addition to other materials) or the environment of the drug is modified by changes in storage conditions, the stability of a drug may be affected [1-5]. Although there are exceptions, 90% of labeled potency generally is recognized as the minimum acceptable potency level (Gennaro, 2000). Stability testing forms an important part of the process of drug development; it provides evidence on how the quality of drug substance or drug product varies with time under the influence of a variety of environmental factors, such as humidity, temperature, and light. The stability studies of drugs can be performed at the original product (“real-time” tests or long-term tests at specific temperatures and relative humidity representing storage conditions experienced in the distribution chain of the climatic zone(s) of the country or region of the world concerned; accelerated stability tests; pharmacies storage tests) or at remainder doses of these products. The chemical stability is evaluated by testing quantity of drug at different time during the storage (Lund, 1994; USP, 2007). The aim of the stability studies is to determine the shelf life of the product and its optimum storage conditions (Connors et al., 1986; Lund, 1994; The Sixth ICH International Conference on Armonization of Technical Requirements for Registration of Pharmaceuticals for Human Use [ICH], 2003; The United States Pharmacopeia [USP], 2007; Watson, 2005; Yoshioka, 2000). Therefore, the authors have been developing and validating HPTLC methods with the aim of quantification of drugs in dosage forms, suitable for stability and quality control studies, as at original products as at its remainder doses.