Drug-polymer interaction affecting the mechanical properties, adhesion strength and release kinetics of piroxicam-loaded Eudragit E films plasticized with different plasticizers

Abstract

In order to design a self-adhesive drug-loaded film for transdermal application of drugs, piroxicam was used as a model drug and triacetin-plasticized Eudragit E was chosen as a film-forming material. In a previous study, we had examined the effect of secondary plasticizers on the mechanical properties and adhesion strength of drug-free Eudragit E film [1]. In the present study, piroxicam did not serve as a simple model drug, but acted as an additive by molecularly dispersing it in the Eudragit E film. The effect of piroxicam on the mechanical properties, adhesion strength and release kinetics of piroxicam-loaded Eudragit E films plasticized with four secondary plasticizers (polyethylene glycol 200, propylene glycol, diethyl phthalate and oleic acid) was investigated. The results indicated that piroxicam was compatible with Eudragit E. A yellowish, transparent film was formed. The tensile strength decreased but the elongation increased with the increase in plasticizer concentration v.hether Eudragit E film contained piroxicam or not, suggesting the plasticizing efficiency of the plasticizer added. It was also found that the tensile strength of the piroxicam-loaded film was significantly higher and the elongation significantly tower than that of the drug-free film. The drug-polymer interaction between piroxicam and Eudragit E film by intermolecular hydrogen bonding might be responsible for this result. The adhesion strength of the piroxicam-loaded film without secondary plasticizer was significantly lower, but this adhesion strength increased again with the plasticizer concentration. The tendency of the adhesive strength of these piroxicam-loaded films to increase whether plasticized with hydrophilic or hydrophobic plasticizers, was similar, This might be attributed to the decrease in the aggregate force caused by the intermolecular attraction of the polymer, resulting in an increase of the adhesive strength of the film. Piroxicam released from the Eudragit E film with or without secondary plasticizer was mainly dependent on the amount of drug-loaded and showed a rate-controlled release behaviour. The release behaviour of piroxicam from the film can be described by a Higuchi equation for matrix controlled release. All the results demonstrate that the release rate of piroxicam from film clearly increases with the amount of drug-loaded but is only slightly enhanced by the increasing the plasticizer concentration. The release rate of piroxicam from four different films whether plasticized with hydrophilic or Hydrophobic plasticizer was almost the same. The drug-polymer interaction occurring between piroxicam and Eudragit E seems to cause a drag effect, leading to a delay of the piroxicam release from the Eudragit E film.