The Empty Capsule is a drug form (or galenic form) used when the drug (or any other substance to be used by oral way) it contains, has a strong odor or an unpleasant taste that you wishes to mask. It's also used when the drug has a texture not easy to put in the form of tablet.
Normally, the active product must be a dry powder, because the gelatin disaggregates when in contact with water. It's possible to putliquids in a capsule, but only is included in an absorbing substate (aerosil for example), or right before swallowing the capsule (it is the case for essential oils). Therefore, the Gelatin Capsules or Empty Gelatin Capsules are widely used. Nevertheless, the capsules can be filled with oily liquids, but in industrial environment only. It's possible to hide in a capsule a smaller product as a compressed tablet or another smaller capsule, for example for clinical trials (known as in "double blind").
Especially treated capsules "gastro-resistants" or with "enteric coating" allow to avoid the anactivation of a substance by the stomach acidity, or allow to obtain a delayed release, in the intestine.
The capsule is mostly a packaging form easy to realize, with a cheap material, from where its success in hospital, in pharmacies, and even at private individuals doing themselves their mixtures of plants. Thanks to the many combinations of colors that it allows, and with the possibility to print logo and reference n°, the capsule makes it possible to personalize a drug or a food complement, with a marketing aim for example. This personalization is also useful for the poisons centers to recognize a product when there is an intoxication There is also many other more "exotic" uses of the capsules. For example, they are used to store electronics components, or fossils of small size.
Structure
The capsule consists of two encased parts: the "head" and the "body": The body is longer and a little less broad than the head. It is the body that is filled filled with powder, and thus it is the volume of this body which is the normal volume of filling. When one inserts the two parts one in the other (after filling), a light relief allows to block the body in the head, with the result that the filled capsules are less long than the empty capsules.
Composition
The traditional capsule consists of gelatin of ox or pig (this gelatin is obtained by partial hydrolysis of the collagen contained in the bones or the skin); the gelatin can be added with opacifying products (titanium dioxide for example) and with dyes. It can also be simply left transparent.
There is also vegetable capsules, containing modified cellulose (Hydroxypropylmethylcellullose, or "HPMC", or "Hypromellose") which had a certain success at the time of the "mad cow" epidemic (or "ESB|"). It should be noted that the traditional gelatin capsules from now on are guaranteed free from risks related to this disease. The vegetable capsules continue to be preferred for the "bio" products. Finally, there is also capsules made with fish gelatin.
Except that, there are other different kinds of capsules like Halal Capsule, Pearl Capsules, Color Capsule, Hpmc Capsules and Pullulan Capsules.
Size and weight
For the regular capsules, the various sizes go from "000" (largest) to 5 (smallest). There is also much larger capsules, for veterinary use, as well as "lengthened" capsules, or even capsules especially reserved for the clinical trials