Norfloxacin, doxycycline and mefenamic acid have been photolysed with UV-C radiation (254 nm) in the presence and absence of inorganic peroxides (hydrogen peroxide or sodium monopersulfate). Quantum yields in the range (1.1-4.5)x 10(-3) mol Einstein(-1) indicate the low photo-reactivity of these pharmaceuticals. Inorganic peroxides considerably enhanced the contaminants conversion, although no appreciable mineralization could be obtained. A simplistic reaction mechanism for the hydrogen peroxide promoted experiments allowed for a rough estimation of the rate constant between hydroxyl radicals and norfloxacin (k > 1 x 10(9) M-1 s(-1)), doxycycline (k > 1.5 x 10(9) M-1 s(-1)) and mefenamic acid (k > 11.0 x 10(9) M-1 s(-1)). (C) 2009 Elsevier B.V. All rights reserved.