Effect of Microwaves on a nimesulide/BCD solid dispersion

The aim of this work was to test the efficiency of a domestic microwave oven in order to evaluate a simple, rapid and cheap method to modify a chemical system promoting different technological properties to make it more suitable to dissolution and improve availability. The method takes advantage by the absorption of the microwave radiation at 2450 MHz by permanent dipoles (especially water molecules) that undergo to rapid vibration. The systems examined contain nimesulide and beta-cyclodextrin either alone or combined in a solid dispersion. The broad endotherm of de-hydration of a sample of beta cyclodextrin disappears after 4 min microwave irradiation without any apparent change; the same can be observed for the drug. The thermal effect of the microwaves was coupled to the mechanical action of a turboemulsifier obtaining a complete amorphization of the system: in a system containing BCD and nimesulide, kneaded together, and irradiated for 7 min at 400W as above reported, the melting endotherm of the drug reduces its surface area, while its release is dramatically increased: after 8 min the release of nimesulide is complete, while it is released 45% from a physical mixture of the same composition and only 12% from the pure drug.