Introduction

Abstract

“Particle-design engineering” has emerged as a new engineering concept in modern powder technology. Since the early 1980s, micronized active pharmaceutical ingredient (API) powders composed of particles with diameters smaller than 5 μm and exhibiting poor water solubility or dispersible properties have been frequently formulated to improve the bioavailability of original API particles that are larger than around 50 to 100 μm, classified as Class 2 in the biopharmaceutical classification system (BCScriteria [1]. Specifically, fine particles, smaller than 1 μm in diameter, have very large surface energy and specific surface area, resulting in an increased solubility and activity of the original particles. However, it is difficult to disperse such fine particles uniformly in the finished product, due to the segregation caused by their strong cohesive properties. Such fine particle systems should be carefully handled according to the good manufacturing practice (GMP) introduced almost at the same time in the Japanese industry to guarantee the quality of finished products and a reliable manufacturing process. To ensure an optimum process and a suitable formulation for obtaining high-quality pharmaceutical preparations at the industrial scale, the division of Pharmaceutical Preparations and Particulate Design (PPD) [1] was established by the Society of Powder Technology of Japan in cooperation with the Association of Powder Process Industrial Engineering, Japan [2]. As an industry-oriented association, the New Pharmaceutical Technology and Engineering research institute (NPTE Inst.) [3] was first established in Japan in 2005, supported by Powrex Co. Japan. The mission of PPD is to create a new pharmaceutical process and innovative resulting products by paradigm shifting through a particle-design concept, defined as follows: “Particle design is to provide a new function to pharmaceutical preparations or to modify that of pharmaceutical preparations to create innovative medicine or medical device by designing physicochemical properties of particulate material as long as to reserve original chemical properties.” The physicochemical properties of particles are classified as intrinsic primary properties of discrete particles and integrated secondary properties of interacted particles (= powder) and their correlations, as listed in Table 1.1.