Fluorescence spectroscopic behaviour and redox reactions of trifluoperazine (TFP) were studied in aqueous solutions in the presence of silica (SiO) particles. The effect of surface heterogeneity on the secondary reactions of the transients was determined using optical absorption and fluorescence techniques. It appears that electrostatic interaction is the driving force for adsorption of TFP over SiO particle. Contrary to the change in fluorescence intensity with time observed in an aqueous solution, fluorescence intensity of TFP did not change significantly with time over the surface of SiO . Fluorescence microscopic observations of spleen cells treated with TFP over SiO₂ showed that the drug got distributed in cells similar to that observed in homogeneous aqueous solution.