Photostability

Handbook of Pharmaceutical Manufacturing Formulations Semisolid Products 

A systematic approach to photostability testing is recommended, covering, as appropriate, studies such as 

The formal labeling requirements for photolabile drug substances and drug products are established by national/regional requirements. [ICH Q1B] 

The light sources described below may be used for photostability testing. The applicant should either maintain an appropriate control of temperature to minimize the effect of localized temperature changes or include a dark control in the same environment unless otherwise justified. For both options 1 and 2, a pharmaceutical manufacturer or applicant can rely on the spectral distribution specification of the light-source manufacturer. [ICH Q1B] 

For option 2 the same sample should be exposed to both the cool white fluorescent and the near-ultraviolet lamp. 

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Peng Xet al 997 Epitaxial growth of highly luminesoent CdSe/CdS oore/shell nanoorystals with photostability and eleotronio aooessibility J. Am. Chem. Soc. 119 7019... 

When chlorine is employed for outdoor swimming pool sanitation, it is relatively rapidly decomposed by sunlight. Isocyanuric acid stabilizes chlorine by formation of photostable chloroisocyanurates (12). By contrast, bromine is not stabilized by isocyanuric acid. 

Likewise there are no reports of systematic photochemical studies, but the pyrido[2,3-ii]pyrimidine ring system appears relatively photostable, as photolytic removal of D-ribityl and hydroxyethyl A -substituents was employed in structural confirmation studies (74JCS(P1)1225). Photo adducts of deazafiavins with cyclohexadienes have been studied, however (77ZN(B)434), as have several other aspects of deazafiavin photochemistry. 

A closely related reaction is the formation of 5T/-1,3-diazepines 7 when 2-azidopyridines 6B are irradiated in the presence of a base, such as sodium methoxide or diethylamine. The reaction only succeeds in the presence of electron-donating substituents (R = OMe. OPh or NEt2) other 2-azidopyridines exist predominantly in the tetrazolopyridine form 6 A and are photostable.161... 

A number of highly substituted photostable 6//-l,4-diazepines 8 can be obtained by irradiating 4//-l,2-diazepines.188 No details were reported. 

Stability Testing of New Drug Substances and Products Stability Testing Photostability Testing of New Drug Substances and Products Stability Testing for New Dosage Forms... 

Storage conditions will be used. Standard conditions to simulate normal storage are temperatures of 25 or 30 °C and relative humidity of 60 or 65%. A minimum of 12 months real-time data is required for a marketing authorisation application. Real-time data should be supported by accelerated and intermediate stress testing at higher temperature/relative humidity. Photostability should be verified using a single batch. 

GL5 Stability 3 Stability testing photostability testing of new drug substances and products... 

GA is mainly used for fat microencapsulation because it produces stable emulsions in the case of most oils in a wide pH range, and it has the ability to form films (Kenyon, 1995). Barbosa et al., 2005 studied the photostability of the microencapsulated carotenoid bixin in different edible polysaccharide. They found out that microencapsulated bixin in GA was three to four times more stable than the one microencapsulated with maltodextrin, and about ten-fold than in homogeneous solvents. 

Methyl 4-[2-(ethylthiocarbonyl)ethenyl]cinnamate (3 SMe) crystallizes into a typical a-translation-type packing structure in which the distances between the ethylenic double bonds are 3.988 A and 4.067 A, respectively. However, the 3 SMe crystal is entirely photostable even though it should be photoreactive based on the topochemical rule (Sukegawa, 1991). Several examples of exceptionally photostable diolefin crystals have been found in compounds having a thioester moiety. Such anomalous behaviour of crystals such as 2 OMe and 3 SMe cannot be explained simply in terms of the topochemical rule since this rule involves only the positional relationship between the reactive olefin pair. 

In previous studies in the author s laboratory it has become clear that, in most diolefin derivatives, replacement of the oxygen atom of an ester moiety by a sulfur atom is possible without changing the photopolymerizable molecular arrangement, and that all of the thioester derivatives and even mixed crystals of the ester containing a small amount of thioester derivatives of 1,4-phenylene diacrylate (PDA) are photostable (Hasegawa et al., unpublished data). 

From the results of the fluorescence spectroscopic study it is concluded that excitation energy at the lowest excited state of a PDA derivative having a thioester moiety is localized at the thioester group intra- or inter-molecular energy transfer from the conjugated system of the PDA to the thioester moiety must have occurred in the crystalline state to afford a photostable crystal (Hasegawa et al., unpublished data). 

The photoreaction of 2,3-distyrylpyrazine (2,3-DSP) derivatives has been investigated in the crystalline state (Tsutsumi et al., 1991 Takeuchi et al., 1993). On photoirradiation, 2,3-di(4-chlorostyryl)pyrazine and 2,3-di(4-cyanostyryl)pyrazine crystals give eight-membered [2.2]orthocyclophanes in 76 and 56% yields, respectively (Scheme 14). On the other hand, 2,3-DSP and 4-nitro or 4-methyl derivatives of 2,3-DSP are photostable in the crystalline state. These results are reasonably interpreted on the basis of X-ray crystallographic analysis of these crystals. 

Kopas-Lane, L.M. and Warthesen, J.J., Carotenoid photostability in raw spinach and carrots during cold storage, J. Food ScL, 60, 773, 1995. 

Jung, H., Kim, C., and Shin, C.S., Enhanced photostability of Monascus pigments derived with various amino acids via fermentation, J. Agric. Food Chem., 53, 7108, 2005. 

When the reaction of [AujCgFsjjtht)] is carried out with C6F4NCSPPh2 the complex [56] shovm in Figure 3.5 was obtained and its structure was determined by X-ray diffraction. The benzothiazole ligands are known to display photophysical properties vdth an improvement of the photostability and emission intensity in conjugated systems as well as in the complexes that contain them, and the presence of... 

J.H. Massey and S.K. Singles, Photostability of two fungicides on spray application monitors, in Terrestrial Field Dissipation Studies Design, Interpretation and Purpose, ed. E.L. Arthur, V.E. Clay, and A. Barefoot, ACS Symposium Series No. 842, American Chemical Society, Washington, DC (2003). 

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