Dietary Supplements in Tablet Format

There are multiple ways of delivering dietary supplements. Consumers now have the choices of powders, liquids, pre-packaged beverages, soft gelatin capsules, hard gelatin and vegetarian component capsules, and varieties of tablets, also known as solid-dosage forms.

Originally, drugs that were developed as painkillers were compressed into tablet forms to allow pre-measured doses and greater portability. Their use was widespread in battlefield conditions by medical personnel attending to wounded combatants. The most powerful of these substances were opiates, such as morphine or codeine, and later variations of these products that are synthesized, such as Vicodin, Lordan and Percocet, oxycodone and others. The German chemist Friedrich Bayer isolated the compound found naturally in the bark of the white willow tree, salicylic acid, and created the first compression of aspirin, which is still the most commonly used drug in the world.

The advent of dietary supplements first became widespread after the discovery of compounds known as vitamins, and has been widely formulated to include other components essential to human metabolism, such as minerals, micronutrients and related pigments or phenols.

Of paramount concern to the formulator of dietary supplements is the requirement to maintain a stable finished product that will appropriately release the contents into the alimentary canal at appropriate points of absorption and utilization. Radiologists often spot undigested and undissolved dietary supplements in X-rays taken of human intestines, particularly in people complaining of digestive discomfort. It is therefore essential that tablets be properly formulated and tested to demonstrate compliance with disintegration and dissolution requirements established by the United States Pharmacopeia (USP), the group responsible for setting manufacturing and testing standards for many common dietary supplements of vitamins and minerals.

In order to be effective in the human body, if the tablet is not enterically coated (meaning it is designed to pass through the stomach without breaking down in the harsh acidic environment, but rather in the small intestine for absorption requirements) or if the tablet is not a “sustained-release" product (intended to release active components over a graduated period of several hours), the tablet must break down (dissolve) within 30 minutes of ingestion. You can perform a simple test of this yourself. First, take a cup of water and heat it to approximately body temperature—just under 100 degrees Fahrenheit. Then drop the tablet into the cup and stir the liquid, being careful not to touch the tablet with the stirrer. Most tablets will disintegrate within a few minutes of ingestion, so do not be surprised to see the tablet disintegrate in less than 15 minutes. But if it takes up to 30 minutes, it will still pass the USP test for disintegration. This does not apply to chewable tablets, which have an entirely separate form of evaluation.

The dissolution of a tablet refers to releasing the nutrients or components of the tablet into the gut to allow the body to absorb the nutrients along the specific sites of the human gut where the villi interface with food nutrients. This is not a test that can be conducted in the kitchen, but requires sophisticated laboratory equipment, specific pH adjusted fluids, and specific test and assay requirements.

As industry formulates products into tablet format, manufacturers should make certain the finished tablet has at least 100 percent of the label claim of the nutrient label. The entire process of making a tablet requires compression in a confined space, where an upper punch and a lower punch press together from opposite directions within a die at specific pressure, sometimes up to six tons, to create the finished tablet. Formulators need to take into consideration the generation of heat through the physics associated with incredible pressure of forming the tablet. That heat is often deleterious to sensitive components in tablets, so the formulator must provide overages of these sensitive nutrients to assure product potency.

Compounds that are sensitive to heat, moisture or ultraviolet light also need to be protected in the tablet environment, which is why many tablets go through an extra process of film coating involving a protein or polymer, and usually with a finished thickness of between 20 and 100 micrometers (very small thickness). The reason tablets are often coated is to protect the ingredients from decay, to help reduce tablet edges from eroding during packaging and transportation, and to mask unpleasant taste or aroma of ingredients. In some cases, the formulators need to place additional components in the coating solution to protect the tablet in the harsh environment of the stomach in order to release sensitive components into the chyme of the small intestine. This type of coating is called an enteric coating. One of the first enteric coatings deployed was in aspirin, because aspirin can lead to stomach lining ulceration in some sensitive patients.

Under U.S. law, if a product has a stated shelf life of one or two years, and an expiration date, the nutrients listed in the Supplement Fact panel must be present at levels at least 100 percent of claim at the end of this shelf life, and producers need to provide written evidence of that fact when requested. Failure to provide this evidence means that the product was not produced under GMPs (good manufacturing practices), and that is a violation of law in the United States. It also subjects the finished product to the allegation by FDA or local health authorities that the product is misbranded and therefore should not be sold.

Tablets that have discolored or appear to “rust" should not be consumed. Tablets that are broken in the bottle or finished package should likewise be considered suspect, especially if the intact tablets are film coated or color coated in some fashion.

The world of tablet compression and preparation is a complex one indeed. Not only do companies have to take into consideration issues of shelf life, stability, exposure to UV rays, oxygen, etc.; they must also elect the appropriate tablet processing aids to actually create the compressibility of the compound. These aids are often known as excipients, because they are not nutritive, per se. Common excipients are forms of sugar such as sucrose or dextrose (often used in chewable tablets), maltodextrin or micronized cellulose powder (for compression binding, to provide a matrix to hold the nutrients and the tablet together), lubricants such as vegetable- or metallic-derived fatty acid molecules (stearic acid, magnesium stearate), disintegrants (such as croscarmellose sodium, starch or starch derivatives) and finally, glidant agents such as silicon dioxide, which helps a sticky powder to flow more efficiently into the compression chambers and allow uniform compression.

Clearly, there is much more to the science of tablet manufacturing than meets the eye, and the consumer needs to be informed regarding these critical components, as well as many of the hallmarks of well-made products versus those of questionable value.

Mark A. LeDoux is founder, chairman and chief executive officer of Natural Alternatives International Inc., an organization with facilities in the United States and Switzerland engaged in the research, design and manufacture of nutritional supplement programs and products for multinational clients.