Theophylline formulation by supercritical antisolvents

Supercritical antisolvent precipitation has been used to produce theophylline particles as pure crystals or as a solid formulation with poly lactic acid (PLA). Experiments were carried out as batch or semi-continuous process and with carbon dioxide (CO2) or trifluoromethane (CHF3) as antisolvent. Both modes led to micronized theophylline, but the semi-continuous produced smaller particles than the batch. The particle morphology was sensitive to the antisolvent, since CO2- and CHF3-samples exhibited hexagonal and triangular shape, respectively. The most distinguish feature of CO2-powders was that theophylline exhibited a different crystal lattice than the crude- or the CHF3-materials, accredited by new diffraction peaks in the XRD patterns not attributable to hydration of samples. However, neither the shape nor the new crystal lattice influenced the dissolution kinetics of Theophylline. For co-precipitation with PLA, the successful recovery of a powder occurred only in conditions of CHF3-batch and CO2-semi continuous. The powder retained the shape and the crystallinity of the corresponding pure processed theophylline, indicating that PLA did not interfere with the precipitation behavior of the drug. Moreover, only the CO2-semi continuous products exhibited a decreased release rate and a prolongation of the total release time of the drug.