Photoallergenic potential testing by online irradiation and HPLC.

: A simple screening method was developed for testing the photoallergenic potential of drugs. The photolysis of the drugs under UV-A irradiation was investigated in aqueous buffer solution alone and in combination with a model dipeptide. As an useful tool for this, high performance liquid chromatography (HPLC) based on an automated column-switching system with aqueous online UV-A irradiation was used. For testing the system, hydrochlorothiazide (HC) with well-known photoallergenic properties was used as a drug and alanyltryptophane (ALATRP) as a model for proteins. Promethazine (PMZ) as a second drug was investigated by the developed screening system. The screening was performed at pH 3 and pH 7. Both cleavage of the peptide binding and formation of new products could indicate a photoallergenic potential.