A REVIEW REPORT ON: COATING OF SOFT GELATIN CAPSULES
A REVIEW REPORT ON: COATING OF SOFT GELATIN CAPSULES

Highly developed soft capsules are currently being applied widely in the pharmaceutical, chemical, food and cosmetic industry. This is attributed to the features of softgels like desirable aesthetic properties and ‘swallowability’, safety enclosure, precise contents, and pleasing appearance. This has enabled their use as an effective delivery system for hydrophobic drugs, low melting-point drugs, easy-oxidized drugs, and a variety of health care oil. Since the introduction of Soft Capsule Making Machine in the 1970s, formulations have continually become more popular with rapid developments in recent years. This could be illustrated by emergency of a more than 560 sets of soft capsule making machine with transfer mode having a production rate of up to 60 billion pills/year (i.e.more than 3600 kinds of drugs) in the world. Up to now, there are more than 30 manufacturers producing more than 40 kinds of soft capsules by using over 60 sets of advanced machines. Softgels’ ability to enhance bioavailability not only makes them the preferred dosage form for new chemical entities with poor oral bioavailability, they can also be used for reformulation of existing drugs, with the purpose of life-cycle extension.

The softgel delivery system is a unitary package, formed with gelatin outer layers, which contain between them the active ingredients in solution, suspension or paste form. Hydrophobic drugs do not dissolve readily in water, gastric or intestinal fluid. When they are compounded in solid dosage forms, their dissolution rate is usually low and absorption varies resulting in poor bioavailability. Bioavailability of these drugs can be improved in the presence of fatty acids e.g. mono or diglycerides. Fatty acids do solubilize hydrophobic drugs in the gut and enable more rapid absorption. The softgel delivers drugs in solution and yet offers solid dosage form. These hydrophobic drugs are dissolved in a hydrophilic solvent, which, when crushed or chewed, releases the drug immediately to produce a solution of the drug in gastric juice ready for absorption from the gastrointestinal tract into the blood stream. This results in rapid onset of desired therapeutic effects6. For example, Ibuprofen soft gel gives rise to a shorter time to peak plasma concentration and greater peak plasma concentration compared to a marketed tablet formulation. Cyclosporine does give therapeutic blood levels which are not achievable from tablet form. Similarly oral hypoglycemic glipizide in softgel is also known to have better bioavailability results compared with tablet form. Softgel delivery systems can also incorporate phospholipids or polymers or natural gums to entrap the drug active in the gelatin layer with an outer coating to give desired delayed/control release effects.

The designs for a specific soft gelatin capsule formulation involve appropriate selection of the shell and fill composition. This is followed by optimization of the two to allow for efficient production of a chemically and physically stable product with the desired biopharmaceutical properties. The shell of a soft gelatin capsule is composed of gelatin, a plasticizer or a combination of plasticizers and water. In addition, it may contain preservatives, coloring and opacifying agents, flavorings and sweeteners, possibly sugars to impart chewable characteristics to the shell, gastroresistant substances and in special cases even active compounds8.The formulation of the fill is individually developed to fulfill the requirements for optimum therapeutic action.This entails optimizing the chemical stability of the active compound to improve bioavailability. Emphasis is also put on efficient and safe filling process in order to achieve a physically stable capsule product. http://www.jiangnan.co/