Hiroaki Okada

Bio: Hiroaki Okada is an academic researcher from Tokyo University of Pharmacy and Life Sciences. The author has contributed to research in topics: PLGA & Glycolic acid. The author has an hindex of 44, co-authored 128 publications receiving 6979 citations. Previous affiliations of Hiroaki Okada include Wako Pure Chemical Industries, Ltd & Takeda Pharmaceutical Company.

A New Technique to Efficiently Entrap Leuprolide Acetate into Microcapsules of Polylactic Acid or Copoly(Lactic/Glycolic) Acid

Abstract: The aim of this work was to develop injectable microcapsules containing leuprolide acetate, that would deliver that drug at a zero-order rate over a period of about one month. A large amount of leuprolide acetate, a hydrophilic drug, was entrapped into polylactic aicd (PLA) and copoly-(lactic/glycolic) acid (PLGA) microcapsules prepared by an in-water dring method using a (w/o)/w emulsion. The basic techniques were designed to increase the viwcosities of the inner water phase and w/o emulsion. Under the conditions used, it was possible for the drug to be completely entrapped by the microcapsules in the range of 10 to 20% on the basis of the polymer. However, the release profiles of the drug in vitro were inadequate for controlled release for one month.

Biodegradable microspheres in drug delivery.

Abstract: General aspects of biodegradable microspheres prepared from natural and synthesized polymers used in drug delivery systems are reviewed first from various viewpoints: characteristics of biodegradable polymers (physicochemical properties, bioerosion mechanism, biocompatibility), preparation method for the microspheres, drug release from parenteral products and briefly nonparenteral products. The relationship between release pattern and pharmacological activity of therapeutic peptides and proteins and rational controlled release design are also discussed. In the latter half, successful sustained release depot formulations of peptides, leuprorelin acetate, and thyrotropin-releasing hormone (TRH), utilizing poly(lactic acid) (PLA) and poly(lactic/glycolic acid) (PLGA) microspheres are reviewed with respect to preparation, drug release, biocompatibility, pharmacological effects, and results of clinical studies. Thereafter, studies on antitumor therapy by chemoembolization using PLGA microspheres containing an angiogenesis inhibitor (TNP-470) are described as an example of targeted drug delivery with biodegradable microspheres.

Prolonged release microcapsule and its production

Abstract: A microcapsule produced by preparing a water-in-oil emulsion comprising an inner aqueous layer containing said water-soluble drug and a drug retaining substance therefor and an oil layer containing a polymer substance, then thickening or solidifying said inner aqueous layer to a viscosity of not lower than about 5000 centiposes and finally subjecting the resulting emulsion to in water drying gives prolonged release of water-soluble drug.

Sustained-release preparation capable of releasing a physiologically active substance

Abstract: Disclosed is a sustained-release preparation comprising 1) a polymer of lactic acid having a weight-average molecular weight of about 25,000 to about 60,000 and 2) a physiologically active substance, and which releases the physiologically active substance over a period of at least about 5 months; the sustained-release preparation shows an almost continuous zero order release of the physiologically active substance over a period of as long as about 5 months.

New methods of drug delivery.

Abstract: Conventional forms of drug administration generally rely on pills, eye drops, ointments, and intravenous solutions. Recently, a number of novel drug delivery approaches have been developed. These approaches include drug modification by chemical means, drug entrapment in small vesicles that are injected into the bloodstream, and drug entrapment within pumps or polymeric materials that are placed in desired bodily compartments (for example, the eye or beneath the skin). These techniques have already led to delivery systems that improve human health, and continued research may revolutionize the way many drugs are delivered.

Biomedical Applications of Biodegradable Polymers

Abstract: Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clinically as surgical sutures and implants. In order to fit functional demand, materials with desired physical, chemical, biological, biomechanical and degradation properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications.