Herbal dosage forms

Herbs are consumed in various ways, most commonly in the form of a tea or tisane prepared from the dried plant material. Both of these terms refer to what is technically known as an infusion, prepared by pouring boiling water over the herb and allowing it to steep for a period of time. In such cases, the herb and the water are not boiled together. Time of steeping is important, for many of the desired components are not very water soluble. For example, in the case of chamomile, where much of the desired activ- ity is present in the volatile oil, even a prolonged steeping of ten minutes extracts only about 10–15 percent of the desired components. 24

Occasionally, an herbal preparation is made by boiling the plant material in water for a period of time, then straining and drinking the resulting extract. Technically, the process is called decocting, and the resulting liquid is known as a decoction. Boiled coffee is prepared in this way as opposed to beverage tea, which is an infusion.

The quantity of herb to be extracted is usually rather imprecise, being stated in terms of level or heaping teaspoonfuls. A standard teaspoonful of water weighs about 5 g (approximately 1/6 oz) and a heaping teaspoonful of most herbal materials approximately half that (2.5 g). Very light herbs such as the flower heads of chamomile may weigh only 1.0 g per heaping teaspoonful. The same quantity of a leaf drug might weigh

1.5 g and of a root or bark about 4.5 g. Even these weights are variable according to the degree of comminution (chopping or grinding) of the plant material. Finely powdered herbs are obviously going to have less space among the particles, and an equal volume will weigh more. A heaping teaspoonful of finely powdered ginger weighs about 5 g. Standard instructions for the preparation of a tea call for one heaping teaspoonful per cup of water (240 mL or 8 oz). It must be noted that the stated sizes of teaspoons are those established by long-standing convention. Experience indicates that modern teaspoons have a capacity some 25 percent greater

than these standards. 25 For most herbal preparations, this difference is probably of minor significance. As previously noted, herbs are often marketed as phytomedicinals in various dosage forms. Some of the more common ones include powders in hard gelatin capsules or, together with suitable fillers and binders, as compressed tablets. When the active principles are not soluble in water or when a more concentrated product is required to allow adequate dosage, various extracts of herbs are prepared. These are usually hydroalcoholic solutions or tinctures of such concentration that 10 mL will contain the active constituents in either 1 or 2 g of herb. Even more concentrated preparations are known as fluidextracts, 1 mL of which represents 1 g of plant material. Tinctures or fluidextracts are consumed as such or by diluting

a specific quantity—usually a certain number of drops—in water so that

Chapter one: Basic principles

15 it may be easily swallowed. The most concentrated form of an herb is a

solid extract prepared by evaporating all of the solvent used to remove the active constituents from the herb. Extracts are often available in powdered form; 1 g usually represents 2–8 g of the starting material. They are nor- mally encapsulated for ease in administration.

If consumers decide to purchase the herbs themselves, rather than

a processed dosage form, they should remember certain guidelines that will help ensure the acquisition of a quality product. Lacking expert knowledge, however, there is no sure way to avoid all of the pitfalls. Buying clean, dried herbs that are as fresh as possible from a reputable source—preferably in a form allowing positive identification—and ensur- ing freedom from insect infestation by careful inspection is probably the best general advice. Many herbs are valued for their aromatic principles. These are stable in whole plant parts for a longer period of time than in finely powdered material. Such plant parts can easily be reduced to the desired fineness in a small electric coffee grinder just before making a tea. Maintain all herbs in tightly closed, preferably glass containers, away from sunlight and in a cool, dry place.

Herbal dosage forms