Complementary medicines

Last updated: February 07, 2020

1. Herbal medicine

Aloe vera
Herbalists use plant-derived medicines at doses where true pharmacological effects can occur and can be measured. (This is in contrast to homeopathic medicine.) For example, the herbal product guarana comes from a plant Paullinia cupana which naturally contains large amounts of caffeine so it is taken to produce wakefulness, but it can also produce the side effects of caffeine such as insomnia and anxiety. Conversely, valerian is from the flower Valeriana officinalis and its constituents have CNS depressant actions so it is taken as a sedative. This means it can generate unwanted sleepiness as a side effect and it has even been reported to cause a withdrawal-type reaction after long-term use, similar to benzodiazepines.

Herbal products may be administered by various routes. Usually they are taken orally, but Aloe vera, is an example that is commonly applied topically, and mistletoe (Viscum album) is sometimes given by injection.

Kava-kava    Courtesy of Wowbobwow12 via Wikimedia Commons
Many patients perceive herbal medicines as ‘safe’ because they occur naturally. However, some herbal medicines can be potentially harmful at therapeutic doses, e.g. kava-kava, now banned in the UK, can cause hepatotoxicity; St John’s wort can interact with many conventional medicines.

In addition, the quality of some unregulated herbal products such as those used in traditional medicine may be causes of harm. Potential problems include:

✦  Failure of good manufacturing practice; incomplete or inaccurate labelling sometimes leading to inability to identify the product or its ingredients; incorrect dosage or instructions.
✦  Adulteration (e.g. inclusion of pharmaceuticals or toxic metals); mis-identification of herbs; substitution (i.e. different herb used to that which is supposed to be in the preparation); varying strengths of active ingredient between brands or batches (e.g. for St John’s wort preparations).

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