Gelatin capsules are one of the ways medications and supplements are formulated for oral consumption. Encapsulation protects the active ingredients in gelatin capsules from exposure to outside contaminants, environmental degradation and possible loss or exposure to unwilling parties. Manufacturers describe gel capsules by their texture and the manufacturing process. Consumers choose gel capsules for their ease of digestion or palatability. Despite these differences, little variation exists between the types of gelatin capsules available on the market.
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Two types of gelatin capsule textures exist: hard gel capsules and soft gel capsules. Hard gelatin capsules usually contain dry or powdered medications or supplements, whereas soft gelatin capsules typically contain oils or solutions in which the active ingredient is mixed with or dissolved in oil, according to the book “Pharmaceutical Capsules,” edited by Fridrun Podczeck and Brian E. Jones. Some people prefer one type of gel capsule over the other for ease of swallowing, storage and shelf life or feel.
Gel capsules come in one or two pieces. Soft gelatin capsules are always one-piece capsules. Although the initial rudimentary process for manufacturing soft gels was patented in 1834 by Mothes and Dublanc, modern one-piece gelatin capsules are manufactured using variations on a process patented in 1933 by R.P. Scherer. One-piece gel capsules provide a distinct advantage to workers dealing with potent drugs, according to Mark Gibson's book “Pharmaceutical Preformulation and Formulation: A Practical Guide.” Since workers can easily reclose the capsule, they can inject the drugs into the gel capsules without exposing themselves to the drugs.
First patented by James Murdock in 1847, two-piece gelatin capsules are manufactured from gelatin that dries hard. Two-piece gel capsules are molded in two separate pieces and sealed back together. The supplier of the drug or supplement purchases the gel capsules and separates them again for the insertion of the drug or supplement powder. The company filling the capsules recloses the gel capsule. The powdered drug or supplement is placed inside the capsule by pouring a premeasured dose into one end of the capsule and closing it; alternatively, a compressed slug in the shape of half of the capsule is placed inside, a process outlined in "Encyclopedia of Pharmaceutical Technology: Volume 5." The second method decreases losses associated with spilled powder but requires the use of more complex machinery.
Gelatin is the substance that encapsulates normal gel capsules. Gelatin itself is manufactured from collagen harvested from animal skin or bones. Despite a popular misconception, hooves are not used in the manufacture of gelatin because they are made of a different substance called keratin, which does not gel in the same way as collagen. The use of animal skin and bones presents a problem for vegetarians, vegans and those observing certain religious laws. In order to meet this niche market, vegetarian gel capsules are also available. According to "Modern Pharmaceutics, Fifth Edition, Volume 1," vegetarian gel caps are made from a modified form of cellulose called hypromellose.