In glassforming organic materials, the addition of water usually has a direct plasticizing effect, visible in a lowering of the glass-transition temperature Tg upon hydration of the material (the lower the Tg the higher the relative water content). We have observed an antiplasticizing effect in a small molecule, prilocaine, caused by the addition of water. This shift in Tg has been observed both with Differential Scanning Calorimetry experiments and Broadband Dielectric Spectroscopy. The microscopic hydrating mechanisms underlying the macroscopic antiplasticizing effect upon the addition of water to prilocaine are still unknown. Here we propose to investigate the hydration structure of prilocaine in solution using neutron diffraction coupled with both EPSR and Molecular dynamics simulations.