Manufacturing hard gelatin capsules

Fig. 1 View of a hard gelatin capsule manufacturing machine. (Courtesy of Elanco Qualicaps, formerly a Division of Eli Lilly Co., Indianapolis, IN)... 

LC Lappas. The manufacture of hard gelatin capsules, paper presented to Research and Development Section, The American Drug Manufacturers Association, Atlantic City, NJ, October 8, 1954. 

I. Cherrette, J. Plaizier-Vercammen, Evaluation of a water dispersion of aquateric for its enteric coating properties of hard gelatine capsules manufactured with a fluidized bed technique, Pharm Acta Helv 67 227-230 (1992). 

The preparation of powders as dosage forms comprises many steps that are the same as for the preparation of powders used to manufacture other solid dosage forms such as tablets or hard gelatin capsules. 

Good flow properties are a prerequisite for the successful manufacture of both tablets and powder-filled hard gelatin capsules. It is a property of all powders to resist the differential movement between particles when subjected to external stresses. This resistance is due to the cohesive forces between particles. Three principal types of interparticle force have been identified (Harnby et al. 1985) forces due to electrostatic charging, van der Waals forces and forces due to moisture. 

The manufacture of tablets, and to a lesser extent powder-filled hard gelatin capsules, involves the process of powder compaction, the purpose of which is to convert a loose incoherent mass of powder into a single solid object. Knowledge of the behaviour of powders under pressure, and the way in which bonds are formed between particles, is essential for the rational design of formulations. 

After tablets, hard gelatin capsules are the most common solid dosage form. Hard gelatin capsules are rigid two-piece capsules made from gelatin, water and colourants. The capsules are produced as empty shells consisting of a cap and body, which during the manufacture of the finished product are separated, filled with the formulation and then rejoined. 

The manufacture and formulation of hard gelatin capsules has not been the subject of as much research as tabletting, partly because encapsulation unlike compression is not a science shared by many other disciplines. Nevertheless, there has been important work performed on this dosage form, and much of it is captured in Hard Capsules Development and Technology (Ridgway 1987). 

Unlike hard gelatin capsule shells which are manufactured empty and subsequently filled in a separate operation, soft gelatin capsules are manufactured and filled in one operation. This is a specialised process and tends to be performed by a limited number of companies. One consequence, therefore, of selecting a soft gelatin capsule formulation is that the product will probably be manufactured by a contract manufacturer. A desire to keep all manufacturing in-house is one of the reasons for companies considering the use of liquid-filled hard gelatin capsules as an alternative. 

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