Influence of Hydrophilic Co-Monomer on the Drug Release from Hydrogels with Thermosensitive -(isopropyl)acrylamide Derivatives.

Polymers sensitive to external stimuli are intensively studied. They are used for preparation of controlled drug delivery systems for variety of active pharmaceutical ingredients. Poly--isopropyl acrylamide is a temperature sensitive polymer, and its properties have been used to obtain a series of thermally sensitive polymeric structures. The present study evaluates the effect of hydrophilic co-monomer, -(2-hydroxyethyl)acrylamide on the properties of thermosensitive hydrogels with hydroxypropyl methylcellulose and assesses the release rate of the model drug naproxen sodium embedded into the hydrogel. -isopropyl acrylamide derivatives were synthesized by surfactant free precipitation polymerization. The chemical structure of the particles was evaluated via nuclear magnetic resonance spectroscopy, whereas the hydrodynamic diameter was measured by dynamic light scattering method. The molecular weight was determined using the static light scattering. Hydrogel formulations with naproxen sodium were assessed in the terms of model drug release rate at two temperatures: 22 °C and 42 °C, using the pharmacopoeial method. The assessed formulations released lower amounts of drug, as compared to the control formulation, containing only hydroxypropyl methylcellulose as the main hydrophilic component.