title: Sustained release of human growth hormone from microcapsules prepared by a solvent evaporation technique.
abstract: Biodegradable microcapsules for sustained release of recombinant human growth hormone (rhGH) were prepared by a solid-in-oil-in-water (S/O/W) emulsion solvent evaporation technique using lyophilized protein microparticles. The minimum mean particle size of rhGH in S/O dispersions was 2.8-3.0 microm when ammonium acetate was added at molar ratios of 10-20 times against rhGH. High entrapment of rhGH in microcapsules was achieved by incorporating rhGH powder with a smaller particle size obtained by lyophilizing with ammonium acetate. As the particle size of rhGH decreased, the in vivo initial release decreased, while subsequent serum levels of rhGH in sustained release phase were higher. Addition of zinc oxide to microcapsules resulted in higher serum levels than those prepared without zinc oxide, suggesting a stabilizing effect of zinc oxide after subcutaneous injection into rats. The release profile of rhGH from microcapsules was controllable by selecting the proper copoly(DL-lactic/glycolic)acid (PLGA) with L/G ratio and molecular weight. Utilization of rhGH powder with a smaller particle size obtained by lyophilizing with ammonium acetate is essential for preparation of microcapsules with high entrapment and well-controlled sustained release profile with small initial release.
authors.affiliation: Drug Formulation Research Laboratories, Takeda Chemical Industries, Ltd., 2-17-85, Juso-honmachi, Yodogawa-ku, Osaka 532-8686, Japan. takada_shigeyuki@takeda.co.jp
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Takada
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yamagata
authors.forename: Masafumi
authors.initials: M
authors.lastname: Misaki
authors.forename: Keiko
authors.initials: K
authors.lastname: Taira
authors.forename: Tomofumi
authors.initials: T
authors.lastname: Kurokawa
mesh_terms: D000085:Acetates / Q000737:chemistry; D000818:Animals; D002214:Capsules; D003692:Delayed-Action Preparations; D004339:Drug Compounding / Q000379:methods; D004655:Emulsions; D005612:Freeze Drying; D013006:Growth Hormone / Q000008:administration & dosage* / Q000493:pharmacokinetics; D006801:Humans; D007279:Injections, Subcutaneous; D008297:Male; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D011208:Powders; D051381:Rats; D017207:Rats, Sprague-Dawley; D012997:Solvents; D015032:Zinc / Q000008:administration & dosage / Q000493:pharmacokinetics
chemical_list: D000085:Acetates; D002214:Capsules; D003692:Delayed-Action Preparations; D004655:Emulsions; D011208:Powders; D012997:Solvents; D013006:Growth Hormone; D015032:Zinc; C018824:ammonium acetate