A simple and fast solid phase extraction (SPE) method allowing the preconcentration, clean-up, and subsequent separate elution of phenothiazines (chlorpromazine hydrochloride, acetopromazine, and propionylpromazine hydrochloride) and glucocorticoids (dexamethasone, betamethasone acetate, and phenylbutazone) from serum samples has been developed. Both fractions were separately collected and analyzed without any additional treatment by high performance liquid chromatography with UV-Vis. The performance of the complete procedure was satisfactory irrespective of the spiking level with recoveries in the range 64-85% for all analytes investigated but for phenylbutazone (20%). Repeatability, evaluated as the relative standard deviation, was globally better than 12%. LC-MS was used for final confirmation of the results.