The structural information of the active pharmaceutical ingredients and indepth insights on the modes of molecular interactions is very important aspects in drug development. In the present work, the process of the molecular self-assembly of two sulfonylurea oral hypoglycemic drugs, glipizide and gliclazide, has been studied in the solid-state using FTIR spectroscopy. Interaction patterns in the respective crystalline states were obtained from the single crystal data. Quantitation of the studied drugs and their binary mixtures has been performed by integrating the peak areas of the characteristic well resolved CCC bending and ring deformation bands at 1527 and 706 cm-1 for glipizide and gliclazide, respectively. The results from this study provide data that can be used for the preparative process monitoring of glipizide and gliclazide in various dosage forms, and their interactions with pharmaceutical excipients.