Hard Gelatin Capsules

The hard gelatin capsule consists of a base or body and a shorter cap, which fits firmly over the base of the capsule. For human use, eight sizes of capsules are available. The capacity of each size varies according to the combination of drugs and their apparent densities. Capsules are available as clear gelatin capsules or in a variety of colors. The pharmacist can use the different colored capsules to distinguish two capsule formulations for the same patient, or to encapsulate unattractive ingredients. The pharmacist can add a dye to the powder before filling a clear capsule to impart a color for identification or esthetics.

Some types of hard gelatin capsules have a locking cap, which makes it more difficult to reopen the capsule.

To aid in the selection of the appropriate size, a table, with the capacity of five common drugs for that particular size capsule, is printed on the box of the capsules. As a guide, the relative sizes and fill capacities of capsules are given below. By knowing the bulk density of fill material, proper choice of capsule size is usually made easier; however, trial and error soon develops the judgment of the beginning pharmacist.