Controlled Microwave Processing Applied to the Pharmaceutical Formulation of Ibuprofen

The first successful development of controlled microwave processing for pharmaceutical
formulations is presented and illustrated with a model drug (ibuprofen) and two excipients (stearic acid
and polyvinylpyrrolidone). The necessary fine temperature control for formulation with microwave
energy has been achieved using a uniquely modified microwave oven with direct temperature
measurement and pulse-width modulation power control. In addition to comparing microwave and
conventional heating, the effect of the presence of liquid (water) in aiding the mixing of the drug and
excipient during formulation was also investigated. Analysis of the prepared formulations using
differential scanning calorimetry and dissolution studies suggest that microwave and conventional
heating produce similar products when applied to mixtures of ibuprofen and stearic acid. However, the
differences were observed for the ibuprofen and polyvinylpyrrolidone formulation in terms of the
dissolution kinetics. In all cases, the presence of water did not appear to influence the formulation to any
appreciable degree. The application of controllable microwave heating is noteworthy as fine temperature
control opens up opportunities for thermally sensitive materials for which microwave methods have not
been feasible prior to this work.