Photostabilization of Tablets

The influence of the drug concentration, surface area, and sample volume has already been described. As a result, the photostability of a tablet formulation can positively be enhanced by developing small tablets with a high drug concentration (Thoma K, Aman W. In preparation) (4). 

In order to protect photosensitive drugs, the amount of undesirable radiation penetrating the drug molecules must be reduced. One way of protecting drugs is the photostabilization by spectral overlay, which has been successfully applied to drug solutions (12). According to this principle, excipients, with absorption spectra 

This example clearly illustrates the importance of spectral correlation. Daylight behind window glass only contains radiation of wavelengths above and about 310 ran. Due to its better overlay with the absorption spectrum of molsidomine in this region, Eusolex 9020 is a more effective photostabilizer for molsidomine compared to Eusolex 6300 and ferulic acid. 

A combination of the two Eusolex types results in even better photostabilization. The mixture has a higher absorption in the region between 310 nm (lowest wavelength emitted by daylight if filtered by window glass) and 350 nm (absorption limit of molsidomine). 

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