Formulating Softgels

Formulating a softgel is obviously different than producing tablets or capsules. Generally speaking, softgels are a non-aqueous and/or oil-based medium. There are many variables to making softgels, and many times there is no single answer or formula that applies to all situations, since a multitude of factors influence how a softgel will work. Each formula is unique and has its own possibilities and properties.

Good softgels are engineered. Every successful softgel is the result of two formulasthe fill material and the shell material. Unless the formulator understands and formulates the fill material to work successfully with the shell, softgel failure will likely result. A good formulation will optimize the chemical stability and uniformity of the active(s), optimize the physical stability of the shell, and improve the absorption and bioavailability of the active(s).

Understanding Softgel Basics

Softgel capsules are flexible, hermetically sealed (air-tight), one-piece capsules consisting of the liquid fill material and the outer gelatin shell. The shell is comprised of gelatin, plasticizer, water and, sometimes, coloring. The shell is filled with oils and non-aqueous liquids. Oftentimes solids (various powders) are added to the liquid fill (suspensions), forming what are known as paste products. The softgel delivers compounds in solution while offering the convenience of a solid dosage form. Upon ingestion, the gelatin capsule ruptures quickly, releasing its contents. It is important to create a homogeneous fill mixture to ensure content uniformity of each softgel dose. Unlike solids, softgels contain a liquid and do not first have to disintegrate prior to exhibiting any pharmacological action.

There are three basic types of fill materials used in softgels.

There are some fills that pose serious challenges to a softgel delivery system, for example, formulations with very high solid material content or powders with large particle size (<80 mesh). Similarly, materials with a high water content or hydrophilic (hygroscopic or hydroscopic) compounds that have high water affinity pose a challenge since water can migrate from the shell to the fill. Those with high water solubility are also challenging since they may move from the fill to the shell. Moreoever, highly water-soluble compounds pose stability concerns.

Other ingredients that may be contraindicated for softgel fills include: formulations containing high concentrations of various salts, materials with very low molecular weight (i.e. alcohols), materials with very high or low pH, and high viscosity liquids. Finally, formulations containing high amounts of fatty acids may not work effectively, as their acidity and reactive carboxyl groups can create chemical instability.

When examining shell ingredients, it is important to address possible concerns surrounding the use of gelatin. All of the reputable gelatin suppliers in the industry can show documentation that their beef gelatin is BSE free. However, non-animal gelatin is starting to enter the marketplace. Compared to previous generations of non-animal gelatin, newer seaweed extracts show vastly improved strength and stability.

Because of the gelatin formulation, softgels are more susceptible to heat and humidity than their hard shell capsule and tablet counterparts. Great care must be taken during the summer months to ensure the products are properly shipped to protect the softgels from excessive heat and humidity. Generally speaking, softgels should be stored around 60°F at 30-percent to 50-percent relative humidity. During the hot summer months, bulk softgels should be shipped in refrigerated trucks to maintain proper temperature conditions.

Robin Koon, senior vice president, Best Formulations (www.BestFormulations.com), has more than 25 years of pharmaceutical experience in clinical pharmacy as a drug chain executive overseeing operations and managed-care, and in retail mass market; he is licensed by the California State Board of Pharmacy. Eugene Ung, director of marketing, Best Formulations, has a bachelors of science degree in nutritional sciences from Cornell University and more than 10 years experience in the dietary supplement industry.