Capsule (pharmacy)

• Hard-shelled capsules, which contain dry, powdered ingredients or miniature pellets made by e.g. processes of extrusion or spheronization. These are made in two-halves: a smaller-diameter "body" that is filled and then sealed using a larger-diameter "cap".
• Soft-shelled capsules, primarily used for oils and for active ingredients that are dissolved or suspended in oil.

Both of these classes of capsules are made from aqueous solutions of gelling agents, such as animal protein (mainly gelatin) or plant polysaccharides or their derivatives (such as carrageenans and modified forms of starch and cellulose). Other ingredients can be added to the gelling agent solution including plasticizers such as glycerin or sorbitol to decrease the capsule's hardness, coloring agents, preservatives, disintegrants, lubricants and surface treatment.

Since their inception, capsules have been viewed by consumers as the most efficient method of taking medication. For this reason, producers of drugs such as OTC analgesics wanting to emphasize the strength of their product developed the "caplet", a portmanteau of "capsule-shaped tablet", to tie this positive association to more efficiently produced tablet pills, as well as being an easier-to-swallow shape than the usual disk-shaped tablet medication.

Single-piece gel encapsulation ("soft capsules")

In 1833, Mothes and Dublanc were granted a patent for a method to produce a single-piece gelatin capsule that was sealed with a drop of gelatin solution. They used individual iron molds for their process, filling the capsules individually with a medicine dropper. Later on, methods were developed that used sets of plates with pockets to form the capsules. Although some companies still use this method, the equipment is no longer produced commercially. All modern soft-gel encapsulation uses variations of a process developed by R. P. Scherer in 1933. His innovation used a rotary die to produce the capsules. They were then filled by blow molding. This method was high-yield, consistent, and reduced waste.

Softgels can be an effective delivery system for oral drugs, especially poorly soluble drugs. This is because the fill can contain liquid ingredients that help increase the solubility or permeability of the drug across the membranes in the body. Liquid ingredients are difficult to include in any other solid dosage form, such as a tablet. Softgels are also highly suited to potent drugs (for example, where the dose is <100 μg), where the highly reproducible filling process helps ensure each softgel has the same drug content, and because the operators are not exposed to any drug dust during the manufacturing process.

In 1949, the Lederle Laboratories division of the American Cyanamid Company developed the "Accogel" process, allowing powders to be accurately filled into soft gelatin capsules.