Antinociceptive and antipyretic properties of a biocompatible polymer, poly(N-(4-(2-(4-isobutylphenyl) propionyloxy) phenyl) methacrylamide (PolyMIA) (Fig. 1) as a carrier drug has been investigated. This new polyacrylic compound and its monomeric form (MIA) were prepared by coupling methacrylic acid, p-aminophenol and 2-(4-isobutyl phenyl) propionic acid (Ibuprofen, IB) by means of well-known esterification and amidation reactions and finally by free radical polymerization of the monomeric acrylic derivative in solution, using a conventional free-radical initiator. Plasma levels were determined by gas-liquid chromatography (GLC) after the administration of IB, MIA and PolyMIA in mice. The results obtained indicate that PolyMIA acts as a controlled IB delivery system. Practically constant plasma levels of IB, about 20 μg/ml, were obtained at least for 6h after the intraperitoneal administration of PolyMIA. Antinociceptive in vivo tests confirm the existence of a prolonged release of IB from the macromolecular systems. PolyMIA shows a time-extended activity and equal or even higher intensity of antinociceptive effects than that of free IB. In antipyretic test, PolyMIA was the only compound which increased its activity beyond the sixth hour of treatment (84.8%, p < 0.01 vs. control and vs. IB), doubling the traditional IB activity. The appearance of pharmacological activity of PolyMIA in a very short time after administration, seems to indicate that the system could be active in its polymeric form, since the hydrolytic behaviour followed in vitro in alkaline medium, showed a rate of cleavage of the side IB residue much lower than that indicated by the effects observed in vivo.