A delicious, well-presented meal is a pleasure for everyone. When it comes to dietary supplements, these should also be a feast for the eyes. An attractive product leads both to good acceptance and compliance among consumers. Good compliance ensures not only regular intake of the supplements, but can even contribute towards the body being better able to absorb the nutrients these provide. When it comes to pharmaceutical products, it has been proven that the bioavailability of the active ingredients is higher when the patient has a positive attitude towards their medical therapy. In addition to the sensual components, the form of dosage also influences technical characteristics such as shelf life, as it can provide protection against light and air. There are many different forms of dosage, which we shall briefly present in this article as an overview. Over the next few pages, we shall discuss various types of capsules (hard capsules, soft capsules), tablets, as well as the “stick” form of dosage. 

Hard capsules

Hard capsules are particularly well-suited for vitamins and minerals, as well as plant powders and powdered extracts. They consist of two prefabricated halves. The lower half – which is somewhat smaller in diameter and called the “body” -is filled, while the “cap”, larger in diameter, is placed onto the filled lower half like a cap. Fine grooves ensure that the body and cap are tightly sealed, meaning that the capsule cannot fall apart into its two halves and the powder cannot escape through the seam. Capsule shells exist in various sizes. These are internationally standardised. When it comes to dietary supplements, sizes 1, 0, through to 00 are most commonly used. Depending on the density of the powder, hard capsules can generally contain between 290 and 850 mg of material. Hard capsules can be made from various basic materials. The most important of these are gelatine, and HPMC (hydroxypropyl methylcellulose) as a vegetarian alternative. Even organic products can be developed with hard capsules as, according to Annex VIII of Regulation (EC) No. 889/2008, the use of HPMC capsules is permitted as long as the capsule shells contain no other additional ingredients. This is something which is guaranteed in, for example, nature caps®.

Soft capsules

Soft capsules are particularly well-suited for oils, emulsions or other similar materials up to a paste-like consistency. Unlike the two halves of a hard capsule, these capsules are not prefabricated. Instead, they are made directly during the filling process from two ribbons of capsule material which run one on top of the other via the so-called “rotary die” process, which uses rotating rollers. The material which is to be placed inside the capsule is then enclosed in two equally-shaped capsule shells which are tightly sealed with a seam. There are various shapes of capsule: from round, to oval, up to oblong, or even the so-called “twist-off” capsules. These capsules have a small extension which can be manually twisted off. This means that the material inside the capsule can be emptied and consumed through the thus created opening – without also having to consume the capsule. A wide range of sizes is also available, whereby filling quantities of around 1200 mg tend to represent the upper limit of what a person can reasonably be expected to swallow. Soft capsules can be made from gelatine or come from a vegetarian source, e.g. on the basis of carrageenans. Carrageenans are a group of long-chained carbohydrates (polysaccharides) which can be found in the cells of various species of red algae.

The shells of both hard and soft capsules can be kept transparent for an appealing look, can be made opaque using titanium oxide, or can be dyed a variety of colours. An opaque capsule shell offers the contents additional protection from light. Generally, non-chewable capsules considerably undercut the disintegration time of 30 minutes prescribed by the European Pharmacopoeia. 

Gelatine capsules contain a certain percentage of moisture. This can lead to undesirable interactions with very hygroscopic ingredients, such as magnesium oxide or tannins. Hygroscopic powder deprives gelatine capsules of their necessary residual moisture. This makes the capsule shell brittle and fragile. This is something to be inherently kept in mind when developing the formula for a capsule.

The biggest advantages of capsules is that they can be filled without any or with relatively little pressure. Putting thermal stress on the nutrients is another aspect which can be kept to a minimum or avoided entirely. What’s more, the shell not only protects the contents from environmental influences, but also protects our taste receptors from a potentially unpleasant taste. For example, many people prefer fish oil capsules whose surrounding capsule shell prevents the oil from coming into direct contact with the oral mucosa, or hard capsules which encase active substances with healthy bitter substances, thus lending them a form which can be easily ingested.

Tablets

Sometimes, creating a formula for a tablet which is technically optimal requires a complex development process. However, tablets do allow for some variations which a capsule does not offer. Effervescent tablets or tablets with a breakline which allow for them to be broken into smaller pieces are just a few examples. Coatings are another aspect which can be easily implemented among tablets, whether for optical and technical reasons, or to ensure the gastro-resistance of the tablet. After being swallowed, a tablet very quickly disintegrates into increasingly-smaller units until finally dissolving altogether. According to the European Pharmacopoeia, a maximum disintegration time of 15 minutes is to be expected. With film-coated tablets, this is extended to 30 minutes.

High pressure is required to press tablets. This is why not all raw materials are suited for tablets. For example, high pressure can have a negative effect on the oil matrix structure of most oil powders, which leads to free oils escaping either immediately or after a time, a phenomenon which can be seen on the surface of the tablet in the form of “grease stains”.

Here, the gentlest process is the so-called “direct compression”. When the raw materials are suitable for this, these are directly mixed with the tablet excipients and pressed. This means that performing granulation in advance, which is time-consuming, expensive and potentially aggressive towards the contents, need not be carried out.

Sticks

In the field of dietary supplements, sticks are a new and very trendy alternative to capsules and tablets. They are receiving a great deal of interest among consumers. Depending on their concentration, sticks can contain approx. 1 – 10 grams of powder or granules. In this manner, products can also be developed which meet health claims that provide for multiple grams of a substance. One stick can replace many capsules, and the reduction in intake to one portion a day makes a product less complicated and more popular among consumers. A powder stick can be taken individually in accordance with the tastes of the consumer: directly, dissolved in water, juice or milk, stirred into yoghurt or mixed into many other dishes.

Granules and powders have different benefits. While granules can well be mixed together homogeneously, and while they create less fine dust, powders have the advantage of not going through any costly and time-consuming preliminary treatments. Granulation puts strain on the contents due to the drying heat. What’s more, carrier material – usually sugars – and to some extent solvents, need to be added.

As with all forms of stick, it is important that the finished mixture is uniform and free-flowing. What’s more, when it comes to sticks, the components should not have too much of a strong individual taste. Should the basic mixture of ingredients be relatively neutral, this can be easily combined with flavourings, as well as with sweet and fruity-acidic ingredients. This enables a wide range of product diversity, which benefits the consumer. A portion of powder or granulate in the form of a stick is also the ideal form of dosage for those who have problems swallowing capsules or tablets. Individual portions are also easier to carry around with you in a bag than a blister pack or an entire box.

All of these possibilities reflect the individuality of today’s modern, flexible and quick lifestyle. In this manner, dietary supplements are becoming an attractive and, at the same time, practical manner in which we can improve our quality of life with essential nutrients.

Author

Susanne Kühnl is the Projects and Development Manager at Goerlich Pharma GmbH. She completed her studies in food chemistry at the Technical University of Munich and will soon be completing her PhD at the University of Innsbruck on the subject of new anti-inflammatory and immunomodulating natural substances.

November 2013