ABSTRACT
Two-piece hard capsules are one of the most established dosage forms for pharmaceutical products. Two-piece hard capsules have been traditionally made of gelatin, which exhibits unique physicochemical properties of gel and film formation within a very narrow temperature range. The manufacture of two-piece capsules is based on the formation of a thin and consistent film formation on the surface of the dipping pins occurring within seconds of the pins being removed from the polymer solution. To achieve this film formation with hydroxypropyl methylcellulose (HPMC), capsules can be manufactured by two basic principles: thermo-gelation, and gelation through gelling systems. HPMC is a material that is widely used in pharmaceutical product development and manufacturing. One of the basic differences between gelatin and HPMC capsules is a temperature-dependent dissolution profile of the gelatin capsule. With the introduction of HPMC capsules for dry powder inhalation (DPI), several technological advantages that substantially extended the design space of capsule-based DPI systems were achieved.
