CHAPTER 14 Herb Manufacture, Pharmacy, and Dosing
Aplethora of products is available on the market. Why wouldn’t we simply recommend that our clients go and buy one off the shelf for their animal? Quite apart from the standard practice of prescribing according to individual needs, one of our main concerns is whether the practitioner can be confident of product quality. Is it safe? Will it be effective? Quality control is covered in Chapter 8, and integral to this is the matter of how herbs are manufactured. This chapter looks at how herbs are made into various useful forms and how they can be dispensed and dosed appropriately.
GOOD MANUFACTURING PRACTICE
In the first instance then, the source and quality of raw materials play a pivotal role in the quality and stability of herbal preparations. Other factors such as use of fresh or dried plants, season, light exposure, water availability, nutrients, period and time of collection, storage and transportation of raw material, age and part of the plant collected, and methods of collecting, drying, and packing can greatly affect the quality and consequently the therapeutic value of herbal medicines. These factors also account for variability of individual constituents or markers in herbal preparations. This variability is not a feature of conventional drug manufacture.
SOURCES OF HERBS
A third source of herbs may be your own garden. Home production of locally endangered plants lightens the strain of commerce in that plant and provides the herbalist with an opportunity to better study his or her medicine from germination to patient administration. Even if regulatory pressures discourage veterinarians from assuming liability for their home-prepared herbal medicines, the use of home-grown plants in their own personal family pharmacy supports the learning process and is highly recommended for recreation and exercise. An excellent reference for home medicine-makers is Cech (2000).
FORMS OF HERBAL MEDICINES
Veterinarians are usually too busy to make their own herbal medicines, but it is important that they know how the herbs are prepared. Herbal products begin as fresh or dried plant, or as plant extracts (Box 14-1). These preparations form the basis for capsules, tablets, pills, salves, oils, liniments, juices, and tinctures.
Dried Forms
Dried herbs
Tinctures and Liquid/Fluid Extracts
Alcohol is a useful solvent and forms tinctures with nearly unlimited shelf-life, unless precipitation occurs over time. For extraction of water and lipid-soluble herb components, alcohol and water proportions may range from 20 : 80 to 40 : 60 (vodka is conveniently made this way) up to 100% alcohol. The percentage of alcohol needed varies according to the constituents to be dissolved, and good manufacturers vary the alcohol:water ratio to reflect the ideal extract for each individual herb (Table 14-1). For instance, mucilage does not dissolve well in ethanol, so a low alcohol percentage is best at 15% to 25%, and resinous herbs dissolve only in high-alcohol menstruum (90%+). Many herbs extract well in plain 80 proof (40% alcohol) vodka. Tinctures must contain at least 24% to 26% pure alcohol to be well preserved. Some manufacturers decoct herbs that are traditionally used this way (concentrated through multiple boiling water extractions), then preserve with alcohol.
Component | Example Plants | Solubility |
---|---|---|
Alkaloids | Goldenseal, lobelia, bloodroot, corydalis | High solubility in alcohol, low water solubility. Vinegar may enhance extraction |
Essential oils | Peppermint, lavender, thyme, tea tree | High solubility in alcohol, low water and glycerin solubility. Extract well into fixed oils |
Glycosides | Hawthorn, licorice, milk thistle, gentian | Soluble in water and alcohol |
Mucilage | Slippery elm, marshmallow, purslane | Water soluble only and best extracted in cold water; will precipitate if alcohol is added. Usually used fresh or simply dried |
Polysaccharides | Astragalus, mushrooms, boneset, echinacea | Water soluble only, will precipitate if alcohol is added |
Resins | Kava, rosemary, grindelia, propolis, sweetgum | Soluble in alcohol and hot oil; not soluble in water. To make an ointment, use tincture in 95%—100% alcohol; add oil, then gently heat to evaporate the alcohol |
Saponins | Ginseng, wild yam, yucca | Water soluble |
Tannins | Witch hazel, blackberry leaf, self heals | Water and glycerin soluble |
One interesting variation on this theme is to extract some of the herb in 100% alcohol and decoct the other portion of herb, then add the two together at an optimal proportion; presumably, this allows maximal extraction of both water- and alcohol-soluble ingredients. It is wise to know what the concoction smells and tastes like when it is first made, so that one can check for spoilage later.
Glycerin Extracts, Glycerites, and Glycetracts
Supercritical CO2 Extracts
DISPENSING TINCTURES AND FLUID EXTRACTS
Various flavoring agents can be used to improve palatability.