Soft gelatin capsules represent the dosed soft dosage form consisting of the medicine concluded in a cover. Soft capsules can be various form (round, oval, oblong, etc.), the different size, color and consistence of filler. To receive covers of capsules, use the various high-molecular film-forming substances which are characterized by a certain mechanical durability and capable to create elastic films. The most widely modern pharmaceutical industry applies gelatin, thus, the majority of the made capsules are gelatin capsules. To receive a cover of a soft gelatin capsule it is necessary to prepare gelatinous weight, with inclusion in its structure, besides gelatin, various auxiliary ingredients. These ingredients promote improvement of structural and mechanical properties of a cover of the capsule and also protect it from moisture influence, protect from microbic contamination, give it a necessary smell and color and so on. The detailed description of properties of gelatin and characteristics of the excipients included in structure of covers of gelatin capsules can be found in the section on production of firm gelatin capsules. The capsules concluded in a cover medicines, are called "filler".
Soft gelatin capsules are intended for encapsulation of very fluid or pastelike fillers (for example, oils, fats, vitamins, oil or other nonaqueous solutions, suspensions, MAZ - Pasto - or gel substances. Some foreign firms and researchers carried out also works on encapsulation to soft gelatin capsules of solid filler (powders or their mixes), however these developments were irrational and did not gain practical distribution. For giving to filler of capsules of certain technical characteristics and a task to it biopharmaceutical properties, biologically indifferent auxiliary ingredients are entered into composition of filler, except pharmacological active agent.
As a rule, it is the thinners giving necessary optimum volume to filler of capsules. Such indifferent thinner for soft gelatin capsules are vegetable oils, various mixes of polyethylene oxides, is much more rare them the silicone oils and complex component structures containing except specified, the twin-80, propylene glycol, glycerin and others are. If necessary, except above-mentioned, it is possible to enter into fillers also other additives.