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The primary photophysical properties of several antibiotic drugs of the fluoroquinolone class have been studied in order to understand better and rationalize the mechanisms leading to phototoxicity due to these drugs. The light absorption and emission properties of various fluoroquinolones have been characterized and, in most cases, they were found to be dependant on medium conditions such as pH and buffer content. Fluoroquinolones have been found capable of binding to DNA, affecting their emission from the excited state. Light-induced production of excited species by FQs and their subsequent reactivity are thus influenced by the characteristics of the medium. Finally, an unprecedented behaviour has been found for the triplet state of fluoroquinolones ciprofloxacin, sarafloxacin, enoxacin norfloxacin when it is formed in the presence of certain inorganic salts commonly used as buffers. The triplet state formed at the end of the excitation pulse reacts with anions such as phosphate and bicarbonate to form another triplet state of lower energy. This previously unreported effect has implications in the photo toxic potential of fluoroquinolones in cellular environments.