Degradation studies experimental design

Experimental designs also have been used to study the influence of tablet composition and storage conditions on the chemical stability (degradation of the drug) [e.g. 14-17]. 

Kinetic information on the chemical changes of excipient compatibility samples is a direct outcome of most formulation compatibility studies. Because accelerated conditions of thermal and thermal humidity stress are employed, degradation will often occur at these conditions. A brief kinetic evaluation of the data can address the behavior and extent of decay such that degradation data can effectively be utilized to determine levels and conditions of compatibility (96). It is not the aim of this section to recommend full kinetic treatment of decay rather it is to describe simple concepts and exercises that will help the excipient compatibility formulator utilize their data most effectively. Several experimental factors can be included in the initial experimental design of excipient compatibility studies to make kinetic analysis more powerful, and even with small studies having a limited amount of samples for analysis, a brief kinetic treatment of the data is recommended. 

The number of experiments and the experimental design of photostability studies conducted under the "forced degradation studies" are left completely to the judgment of the applicant. Careful studies designed to discover photostability problems early in development could provide significant savings by avoiding costly surprises later on. 

---