Definition
Capsules are solid and single-dose dosage forms of medicine of various shapes and sizes, usually intended for ingestion. This article refers to hard capsules. Soft capsules are covered in a separate article. Hard capsules, unlike them, do not contain plasticizers. Capsules consist of a capsule shell and the filling material, which contains the active ingredient and excipients. They were invented in the 19th century and, like tablets, are among the successors to pills, which are no longer manufactured today. Capsules are important oral dosage forms, but they are used somewhat less frequently than tablets.
Capsule shells
Capsule shells are traditionally made from gelatin of animal origin. Celluloses such as hydroxypropylmethylcellulose (= hypromellose) can also be used as a vegetable alternative. These so-called vegetable capsules are suitable for vegans or people who avoid gelatin for religious reasons. The larger wafer capsules made of starch are hardly used today. The shell may contain excipients such as colorants. The functions of color include protection from light, identification and aesthetics. Dyes or titanium dioxide can be used to make capsules opaque (“opaque”). Capsules can also be printed on the surface for identification or other purposes.
Filling
The filling consists of a single or multiple active ingredients and various excipients. These include fillers such as lactose, mannitol and starch, colorants, and lubricants such as magnesium stearate and silicon dioxide.
Production
Hard capsules consist of two prefabricated cylindrical parts, known in English as the (body) and (cap). These are each terminated at one end with a hemispherical base, while the other end is open. The capsules can be filled with powders, granules, pellets, small tablets (micro tablets) and sometimes even semi-solid preparations and liquids. The content is filled by machine into one of the two parts and closed with the other. It must be compatible with the shell. Capsules can also be produced in small quantities in pharmacies using a manual capsule filling machine. In principle, even laymen with the appropriate equipment can fill capsules. However, due to various risks, we advise against this – see under DIY medications. Empty capsules are available in pharmacies.
Advantages
Capsules can be taken quickly, easily, and discreetly. Unlike liquid medicines, they have a longer shelf life. They require only small packaging, can be stored easily, and contain a defined amount of the active ingredient. Capsules can be produced inexpensively in large quantities. There is no unpleasant odor or taste because the substances are enclosed in a shell.
Disadvantages
Swallowing can be a problem for children, patients with swallowing difficulties, and the elderly, among others. The dose cannot be adjusted individually, or only with restrictions – this, for example, in contrast to drops or other liquid medications. In addition, the active ingredient must be available orally and the effect is delayed.
Can capsules be divided or opened?
Unlike tablets, ordinary hard capsules cannot be divided. However, some can be opened and the contents sprinkled into water or yogurt, for example. The product information will tell you if this is allowed. Opening capsules with an altered release of active ingredient may not be permitted. Opening can also be problematic for drugs with potent active ingredients, such as cytostatics or hormones, and for pregnant women. There may also be an unpleasant odor or taste. The contents may irritate the mucous membranes of the mouth and throat.
Swallowing capsules
To make it easier to swallow capsules, they can be moistened with a little water or saliva. This will make the surface slippery.
Release of capsule contents in the digestive tract.
The gelatin shell of the capsules dissolves at body temperature (about 37°C) in contact with the food pulp. During this process, the active ingredients are released, dissolved or suspended and can be absorbed.
Storage
Capsules are usually stored at room temperature and dry according to the directions in the package insert.If the humidity is too high, the gelatin begins to dissolve. If it is too low, capsules become brittle. Therefore, capsules should be left in the blister or package until before ingestion.