The chapter presents a synthesis of results obtained on resonant interaction of laser radiation with medicines, in bulk, such as: cytostatics (methotrexate, 5-fluorouracil), phenothiazines (thioridazine, promethazine), quinazoline derivative (BG 1188) and hydantoin derivative (SZ-2). The effect of laser radiation on the studied samples is evaluated by analytical techniques out of which steady state absorption spectroscopy, laser induced fluorescence and FTIR spectroscopy, phosphorescence of generated photosensitised singlet oxygen and thin layer chromatography (TLC) used for qualitative photoproducts evidencing are approached. The molecular structural changes are suggested and the obtained photoproducts under laser exposure are analysed by spectroscopic means. This kind of data is related to a new method to combat multiple drug resistance acquired by microorganisms and tumours which develop new chemicals with bactericide or antitumour effects by exposing existing medicines that have low effects or are un-efficient, to laser beams.
Keywords: Absorption spectroscopy, Cytostatics, 5-fluorouracil, FTIR, Hydantoin derivatives, Laser induced fluorescence, Laser photochemistry, Methotrexate, Phenothiazine, Photosensitive medicines, Promethazine, Quinazoline derivatives, Singlet oxygen phosphorescence, Thin layer chromatography, Thioridazine.