CHAPTER 2: Hard Capsules in Modern Drug Delivery
Published:25 Jun 2018
S. Stegemann, W. Tian, M. Morgen, and S. Brown, in Pharmaceutical Formulation: The Science and Technology of Dosage Forms, ed. G. D. Tovey, The Royal Society of Chemistry, 2018, pp. 21-51.
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Hard capsules are one of the oldest and yet most innovative dosage forms, which can address many of the challenges of modern day pharmaceutical development. For many years, hard capsules made of gelatin served as a drug delivery vehicle for different types of oral and pulmonary formulations. Over the past decades capsules made of hydroxypropylmethylcellulose (HPMC) and pullulan have reached the market, which has opened up a range of possibilities for drug delivery in hard capsules. These include HPMC-based hard capsules providing enteric or bioavailability-enhancing properties. Moreover, an understanding of the science behind the manufacturing technologies of hard capsules has advanced, fulfilling the requirements of quality by design as well as allowing further customization of hard capsules to provide capsules with low moisture or low powder retention, which can be critical to their performance in certain applications such as inhalation. With the development of new capsule designs additional applications of hard capsules became viable e.g. the filling of liquid formulations, secure double blinding in clinical trials or the use for sprinkle forms for patients with swallowing issues. As a result, hard capsules are being used globally for a wide range of formulations. Hard capsule technology takes advantage of its flexibility and the simplicity of the manufacturing process, requiring just mixing and filling. In conjunction with the broad range of available small- to large-scale manufacturing equipment and capsule filling technology established around the world, hard capsules play an important role in global healthcare provision.