Forced degradation studies Leading

The use of different photon sources (i.e., QIB Option 1 vs. Option 2) for forced degradation studies and confirmatory studies is not specifically discussed in the ICH guideline however, the use of different photon sources can lead to differences in the photostability results (i.e., different photodegradation rates and potentially different photodegradation profiles). Thus, it may be prudent to use the same photon source for both studies, as was shown in the work of Sequeira and Vozone (4-6). 

Tomita, et al., 1970 Meilhac and Tardy, 1970.) The prevalence of montmorillonites, in river sediments and those studied as deep-sea cores in the numerous JOIDES reports leads one to believe that montmorillonite is a very common weathering product. Certainly a portion of it is derived from degraded micas but if one considers that the next most common sedimentary mineral is illite, one is forced to conclude that either continental rocks are for the major part made of micas or that many other minerals are transformed into montmorillonite during the weathering process. 

The degradation of sterols and related compounds has been extensively studied and, for bile acids, involves a complex sequence of reactions that illustrate additional metabolic possibilities. For compounds oxygenated at C3, initial reactions lead to the formation of the l,4-diene-3-one, but the critical reaction that results in cleavage of the B-ring is hydroxylation at C9 with formation of the 9,10-seco compound under the driving force of aromatiza-tion of the A-ring (Figure 6.17) (Leppik 1989). 

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