Solid capsules are intended for dispensing loose powdery or granular substances. They have the shape of a cylinder with hemispherical ends and consist of two parts: a body and a cap; both parts must fit freely into each other without forming gaps. Hard capsules are filled after the molding process has been fully completed and they have acquired the appropriate elasticity and rigidity. Hard capsules have a two-part structure and can be manufactured in advance and filled with drug substances as needed. Soft capsules are designed for liquid or paste-like drug substances. Capsules have different shapes: spherical, ovoid, oblong or cylindrical with hemispherical ends. Soft capsules got their name due to the fact that in the process of their manufacture, the filler is placed in a still soft elastic shell. The capsules are then subjected to further manufacturing processes that may result in the original elasticity of the shell being partially or completely lost. Such capsules have a one-piece shell, which may be elastic or rigid. Sometimes the shell of soft capsules contains the active substance.Capsules are intended for oral, less often rectal, vaginal and other routes of administration. Depending on the localization of oral capsules are divided into sublingual, gastric-soluble and intestinal-soluble (resistant to the action of gastric juice, but easily destroyed in the environment of the small intestine). Modified-release capsules have special excipients in the contents or shell designed to change the rate or location of release of active ingredients. Intestinal soluble capsules are also classified as modified-release products, which must be stable in gastric juice and release the active ingredients in the intestine. They can be manufactured by coating hard or soft capsules with an acid-resistant shell or by filling capsules with granules or pellets coated with acid-resistant shells.

Currently, the dosage form in the form of gelatin capsules has become very popular with pharmaceutical manufacturers, consumers and physicians due to a number of advantages and positive characteristics. These include, among others:
High dosing accuracy of the drug substances placed in them. Modern equipment ensures high accuracy of filling capsules with filler (with a tolerance not exceeding ±3%) and minimal losses. High bioavailability. Studies have shown that capsules often disintegrate faster in the human body than tablets or dragees, and their liquid or unabsorbed solid contents are more quickly and easily absorbed. The pharmacological action of the drug substance is manifested in 4-5 min. High stability. Drug substances in capsules are protected from various unfavorable environmental factors – the effects of light, air, moisture, mechanical influences – due to the shell, which provides a sufficiently high tightness and isolation of components. Therefore, in the manufacture of capsules it is possible to avoid the need to use antioxidants or stabilizers or reduce their amount.
Corrective ability – unpleasant taste and odor of medicinal substances is eliminated, which is especially important in pediatrics. High aesthetics – achieved through the use of various dyes in obtaining capsule shells. Today, leading pharmaceutical companies use up to 1,000 different colors and shades for coloring capsule shells.
Possibility to set specific properties of drug substances – creation of intestine-soluble capsules, as well as urethard capsules (with prolonged drug release), which can be achieved by various technological methods.