While hard gelatin capsule formulations for earlyphase studies have many desirable features, they are not commercially viable most of the time.^3,4 The reason for this is that the manufacture of early clinical formulations cannot usually be transferred to large-scale production equipment and, as such, the development of a second drug product for latephase clinical studies that can be manufactured on a large-scale and is chemically compatible, stable and bioavailable, is necessary. Based on economic and certain marketing considerations, tablets are most often formulated for latestage clinical trials and commercialization; they are more tamper-resistant than hard gelatin capsules and may be compressed in a myriad of shapes. Tablets are preferentially film coated to obtain a vast array of aesthetic images and these film coatings may also provide a vehicle for anti-counterfeiting measures (brand security), brand identification, functional characteristics such as odour, oxygen and moisture vapour barriers, and enhancing ease of swallowing. The preference for tablets is borne out by approval statistics from the FDA: from 1996 through to 2006, a total of 10139 tablets and 2700 capsules were approved by the FDA, which corresponds to an approximate 4:1 preference of tablets versus capsules.⁵

The Capsule-to-Tablet formulation concept, owned by Colorcon Inc. (PA, USA), is proposed to reduce the amount of work required to develop capsule and tablet formulations. Ideally, the same formulation would be used in capsules for early clinical phases and, subsequently, in tablets for commercialization. As the excipients are identical, the stability of the clinical capsule formula and commercial tablets should be similar. By using a common formulation, the amount of excipient compatibility testing can be reduced, which would lead to corresponding decreases in analytical testing and report writing. Realizing that the amounts of APIs may be very limited, it is suggested that starting Capsule-to-Tablet formulations be developed based on model drugs that have the same dose and solubility characteristics of the APIs if they are in short supply.