Triprolidine hydrochloride, C19H22N2HClH2O (TPH) is a well-known antihistamine drug, which is reported as being photosensitive. Solid-state photostability studies
of TPH were undertaken by irradiating TPH and its binary mixtures with β-cyclodextrin (BCD) and glucose, using an Atlas Suntest
CPS+ irradiation chamber and conditions according to the guidelines of the International Committee on Harmonization (ICH). HPLC
analysis was used to determine the extent of photodegradation. XRD results showed that changes in the TPH crystal structure
had occurred during irradiation and that these changes increased with the time of irradiation. Although the potential for
isomerization under the influence of UV-light to the pharmaceutically inactive Z-isomer exists, results have proved that this
transformation for solid-state TPH would require more extreme light conditions. The results of this study thus illustrate
the general light stability of TPH in the solid-state.