Herbal Medicine I - Herbal safety Flashcards
Herbal safety
- Herbal medicine is a powerful therapy and full attention must be given to safety:
- Before taking or recommending herbs check for cautions and contraindications. Liquorice root for example can increase blood pressure (therefore avoid for people with hypertension).
- Herbal medicine textbooks provide this information, and checks can be made using the internet. The following is a example database:
- http://www.nlm.nih.gov/medlineplus/druginformation.html
Schedule 20 herbs
- Schedule 20 herbs are a special group of herbs that are subject to usage and legal dosage restrictions:
- Can only be prescribed and dispensed by qualified herbalists.
- Must be kept in a locked cupboard.
- At the correct dose they are completely safe, but at higher doses they are poisons!
- Don’t take Schedule 20 herbs unless prescribed to you by a qualified herbalist, or recommend them to anyone unless you are a qualified herbalist.
Schedule 20 herbs Examples
A full schedule 20 list has been provided with your lecture notes, but it includes the following herbs:
* Aconite (pain) external use only.
* Arnica**(pain, inflammation) external use only.
* Deadly nightshade (gastro-intestinal pain).
* Lily of the valley (heart failure).
* Ephedra (allergy).
* Gelsemium (pain).
* Henbane (severe uterine pain).
* Lobelia (bronchodilator).
Herb allergies
Herb allergies are rare, however our immune systems are becoming increasingly sensitive, so take care:
* People with a ‘ragwort’ allergy may also be allergic to chamomile and feverfew (for migraines).
* With atopic patients (asthma, eczema, hay-fever) test herb drops on the skin of inner wrist / elbow to check for sensitivity. Avoid if there is a reaction.
* If people report side effects from herbs, they should stop taking them, wait till effect passes, try again at ½ dose. If effect happens again —discontinue.
Toxic compounds: Pyrrolizidine alkaloids
Some traditional herbal medicines have been
found to contain toxic compounds:
* For instance, chemicals called ‘pyrrolizidine alkaloids’ (PAs) in the comfrey and borage plant family can damage the liver in high doses. Comfrey root is banned for internal use.
* Borage and comfrey leaf tea / tincture is fine, but:
o Use small doses (½ - 1 teaspoon herb per cup).
o Use for short periods (one month maximum).
o Avoid in all pre-existing liver diseases.
Herbs and Pregnancy / Breastfeeding
Pregnant and breast-feeding women must not take herbal medicines, unless advised by a qualified herbalist:
* Always ask female patients if they are pregnant, could be pregnant, or are breast feeding before recommending they take herbs.
* Simple teas such as peppermint and fresh ginger are traditional remedies for morning sickness.
* Fennel seed is good for breast milk production.
* These are safe in moderation (½ - 1 tsp infused 3 x daily), but not in higher doses!
Considerations in pregnancy: Teratogenic herbs
Some herbs contain a chemical called ‘thujone’ which increases risk of birth defects (teratogenic effect):
E.g. thuja, wormwood, sage, rosemary, thyme, basil (*OK in small culinary amounts).
Considerations in pregnancy: Emmenagogue herbs
Some herbs encourage menstruation:
E.g. agnus castus, angelica, motherwort, yarrow.
Considerations in pregnancy: Laxatives
Strong herbal laxatives (contain anthraquinone glycosides) may increase miscarriage risk:
E.g. senna, rhubarb root, cascara sagrada, aloe root.
Breastfeeding
Nursing mothers must be cautious and evaluate safety of herbal medicines as plant chemicals may enter breast milk, and could adversely affect infant:
- Other unsafe herbs in pregnancy and breast feeding include: celery seed, berberis, blue cohosh, celandine, black cohosh, cinnamon, myrrh, golden seal, juniper, pennyroyal, parsley root, poke root, turmeric, feverfew, mistletoe.
- Check all herbs using texts and reputable databases. Avoid using herbs if there is any doubt, and focus instead on gentler naturopathic tools such as nutrition or homeopathy at this important time.
Herb drug interactions:
Herbal medicines work on the same biochemical pathways as pharmaceuticals, which can lead to ‘herb drug interactions’:
- Many interactions are theoretical only, whilst others are based on animal and test tube (in vitro) research.
- Nevertheless, we need to be cautious.
- Always cross-check herbs and drugs carefully and avoid potential interactions if there is any doubt.
- There will always be safe alternatives.
Additive interactions
‘Additive’ interactions occur when the effect of a herb is the same as a drug, leading to excessive effects:
* Herbal sedative e.g. valerian+ prescription sedative may cause very strong sedation.
* Herbal blood thinner e.g. garlic + warfarin could lead to spontaneous bleeding.
* Herbal hypoglycaemia e.g. gymnema + metformin or insulin could lead to extreme drop in blood sugar.
* Garlic has antiplatelet activity. Therapeutic amounts should be used with caution with antiplatelet and anticoagulant medications.
Antagonistic interactions
‘Antagonistic’ interactions can occur if herbs and drugs have opposite effects, potentially reducing herb or drug efficacy:
* E.g. liquorice and Korean ginseng can raise blood pressure, which could potentially reduce or cancel out the effects of conventional blood-pressure-lowering medicines.
Antagonistic interactions: St John’s Wort
St John’s wort is antagonistic to many drugs because it speeds liver detoxification, so clears drugs from the system faster:
* This is dangerous for patients taking ‘life-maintaining’ medicines such as:
o Immuno-suppressants following organ transplant.
o Digoxin for heart failure.
o Warfarin following stroke.
* May also clear birth control pill out of the system resulting in unplanned pregnancy.
Herbal safety check list:
Before prescribing, check all herbs for safety issues:
* Always ask patients if they are pregnant, could be pregnant, or are breast feeding.
* Always check what medications they are taking.
* If there is a caution or interaction don’t proceed.
* There will be safe ways to support patients using different herbs or different approaches.
* The most up-to-date information is found on databases such as Medlineplushttp://www.nlm.nih.gov/medlineplus/druginformation.html
