Ultrasonic velocity, density, and viscosity have been measured experimentally in the solutions of hydrates in nonaqueous medium i.e., methanol at two temperatures 30 and 40oC. From the derived parameters like internal pressure, adiabatic compressibility, free volume etc., the solute-solvent and solute-solute interactions are estimated. Also in all the three hydrates in methanol, apparent molar volume, apparent molar compressibility are computed and the limiting / partial molar volumes and compressibilities have been obtained to reveal the nature of interactions. Jones – Dole constants also evaluated are of high value in estimating the nature of interactions. On the whole, the dominance of solute-solute interactions in the solutions of levofloxacin hemihydrate is observed. In the solutions of tacrolimus monohydrate, mostly solute-solute interactions and strong solute-solvent interactions in the solutions of lisinopril dihydrate are found to be dominant.