Photoinduced color changes in two different qualities of riboflavin in the solid state and in various tablet formulations photoreactivity of biologically active compounds. XX.

There has been a gradual change in the relative amounts of synthetic and biosynthetic bulk riboflavin (RF) supplied to the overall market over the past years. The two sources of drug substance seem to have different photochemical properties that cannot be readily predicted. Alternating between the two qualities of RF therefore seems to influence the photochemical properties of the final product in a rather unpredictable way. A change in production method introduces the possibility of a change in polymorphic form which may alter the photoreactivity of the substance. The drug substance and tablets become green upon light exposure. The biosynthetic bulk material appears to be less photostable than the synthetic bulk material after inadvertent exposure to radiation or at elevated humidity. The observed color change cannot be explained by the formation of degradation products but is strongly dependent on the humidity level within the drug substance or preparation. The change in color was dramatically increased (by a factor up to 7) when the drug substance was formulated as tablets. Interactions were observed between RF and individual tablet components by mixing and compression at low pressure prior to exposure.