title: Micronization of anti-inflammatory drugs for pulmonary delivery by a controlled crystallization process.
abstract: Jet-milling as the common way for micronization of drugs shows several disadvantages. Drug powder properties are decisive for pulmonary use because, besides a small particle size, a good deagglomeration behavior is required. In this study, several anti-inflammatory drugs [beclomethasone-17,21-dipropionate (BDP), betamethasone-17-valerate (BV), triamcinolone acetonide, ECU-R2, budesonide, and prednisolone] were micronized by controlled crystallization without any milling processes. First the drug is dissolved in an organic solvent (BDP/BV: 4%; ECU-R2: 1% in acetone) and precipitated by a solvent change method in the presence of a cellulose ether (hydroxypropylmethylcellulose) as stabilizing hydrocolloid. By rapid pouring the solution of hydroxypropylmethylcellulose in water (BDP/BV: 0.005%; ECU-R2: 0.025%) into the drug solution under stirring in a relationship (v/v) of 1:16 (BDP/BV), 1:4 (ECU-R2), the previously molecularly dispersed drug was associated to small particles and stabilized against crystal growth simultaneously. This dispersion was spray-dried, resulting in a drug powder with a uniform particle-size distribution and a drug load of up to 98% (BDP, BV). The mean particle size of the drug was lower than 5 microm in most cases and consequently in the respirable range. Whereas the fine particle fraction (<5 microm, measured without excipients and without an inhalation device) of jet-milled drugs is 9.5 (BDP) or 13.1 (ECU-R2), fine particle fractions of 25.6% (BDP) resp. 78.2% (ECU-R2) are obtained with the spray-dried powders. As the formation of the small crystals requires a rapid solvent change process, the affinity of the hydrocolloid, and a high difference between the solubility in the solvent and nonsolvent, the drug's partition coefficient limits the method as drugs which are more hydrophilic form larger particles.
authors.affiliation: Department of Pharmaceutics and Biopharmaceutics, Christian Albrecht University Kiel, Gutenbergstr 76, D-24118 Kiel, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Rasenack
authors.forename: Hartwig
authors.initials: H
authors.lastname: Steckel
authors.forename: Bernd W
authors.initials: BW
authors.lastname: Müller
mesh_terms: D000280:Administration, Inhalation; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage*; D003460:Crystallization; D016503:Drug Delivery Systems / Q000295:instrumentation / Q000379:methods*; D008863:Microspheres; D010316:Particle Size; D011208:Powders
chemical_list: D000893:Anti-Inflammatory Agents; D011208:Powders