The disclosure provides a method for quantitatively determining risedronate in a urine sample by adding an internal standard to the urine sample, applying the urine sample to a polymeric water-wettable reverse-phased sorbent preconditioned with methanol, washing the sorbent with TEA in water and formic acid in methanol, eluting risedronate with a mixture of methanol and water containing EDTA under vacuum, evaporating the eluted solution and reconstituting with a mixture of methanol and NH4OH buffer and analyzing the sample with a LC-MS/MS system.