According to the Dietary Supplement Health and Education Act of 1994 (DSHEA), a dietary supplement is defined as a product that is intended to be taken by mouth, in forms such as a tablet, capsule, powder, softgel, gelcap or liquid. Dosage forms are classified in one of two basic ways: 1) the physical state of the ingredient (solid, liquid or gas), or 2) by route of administration (ROA) pathway into the body. Generally, the ROA forms are: enteral (oral, buccal, sublingual and rectal), topical (transdermal), parenteral, inhaled (nasal), vaginal, ophthalmic and otic. Essentially, dietary supplements are designated as enteral orally ingested dosage forms. Many choices and types of oral dosage forms are available. Each of these solid-dosage forms has advantages and disadvantages.

Choosing a delivery form

Consumers have many more choices of dosage forms available these days. Solid dose (tablets/capsules) is still the major oral dosage form sold; however, preferences for other dosage forms continue to grow.

Consumers’ preferences include:

Clearly, the difficulties swallowing tablets or capsules is an issue experienced by a wide range of people regardless of age or gender, with the elderly and young having the most difficulty. More user-friendly dosage forms are now available: chewable tablets, effervescent, lozenges, gummies, powders, liquids and softgels.

Ideally, the key consideration in choosing an oral dosage form is in using one that serves as the optimal vehicle for both metabolic purposes and for maintaining efficacy of the product. Of the oral dosage forms available, tablets and capsules are probably the most well-known and therefore the default choice for healthcare companies. However, marketers are looking for other dosage forms to provide product differentiation, improve product compliance, and give options to their customers. There is a learning curve with these novel dosage forms in terms of product stability, ingredient interaction, supply chain considerations, and overall efficacy of the product.

The selection choice should be based on a consideration of several factors, including functionality (absorption, bioavailability and stability), suitability of ingredients (chemical, form, physical, pH, solubility, etc.) availability of ingredients/excipients, costs involved, and marketing preferences. Some other key considerations are minimal dosage administration frequency, minimal and preferred excipients, convenience and transportability.

Tablet supplementation

A tablet is a compressed solid dosage form containing medicinal or beneficial substances with or without suitable binders or excipients. It may vary in shape, size and weight (i.e., round, oval, oblong, square or wafer). The term (tablet) comes from the French word tablette (little table), and is also sometimes referred to as a “pill." They also come in many forms: soft (chewable), effervescent, lozenge (pastille), multi-layered, control-release (slow-release) and orally disintegrating (quick-dissolve). Further, many of these can be uncoated or coated (film, sugar or enteric).

Buccal and sublingual tablets have had issues with some regulatory experts. Since they do not technically get ingested (absorption occurs in the mouth), some have argued they are not “ingested" oral dosage forms (which are listed above as being “eaten" or “taken by mouth.")

Advantages of tablets:

Disadvantages of tablets:

Capsules

There are two variations when it comes to capsules: hard-shell capsules and softgel capsules. 

Hard-Shell Capsules

A capsule is a solid dosage form in a two-piece gelatin or vegetarian container (shell). Normally used for dry, powdered ingredients and non-aqueous liquids. Capsules typically can be coated, banded or enteric.

Advantages of hard-shell capsules:

Disadvantages of hard-shell capsules

Softgel Capsules

Softgels are a liquid-filled dosage form. Primarily non-aqueous liquids (lipids, polyethylene glycol [PEGs], etc.) are used as an oil fill or to suspend powder ingredients; a great non-aqueous dosage form for oils or oil-based ingredients. The shell can be composed of gelatin (bovine, porcine or piscine) or non-animal (starches, carrageenan, etc.). They can be coated or enteric coated.

Advantages of softgel capsules:

Disadvantages of softgel capsules:

Both hard or soft capsules can be modified-release capsules (including delayed-release capsules [gastro-resistant/enteric capsules] and sustained-release capsules [extended-/prolonged-release capsules]).

Powder supplementation

A solid dosage form that allows for multi-dose preparations consisting of solid, loose, dry particles of varying degrees of fineness. Powders can contain one or more active ingredients, with or without excipients and, if necessary, coloring matter and flavoring, and they can be effervescent.

Advantages of powder supplements:

Disadvantages of powder supplements:

Liquid supplementation

There are various formats when it comes to liquid supplementation. 

Advantages of liquid supplements: 

Disadvantages of liquid supplemets:

Robin Koon is executive vice president at Best Formulations, and has more than 35 years of pharmaceutical experience in clinical pharmacy, as a retail drug chain executive, in managed-care and in manufacturing.