DRUG / NUTRIENT INTERACTIONS
The growing research into the proven benefits and safety
of dietary supplements and herbs has led to a significant
increase in their use over the past decade. It is the issue
of the combined use of natural and drug treatments that
is perhaps the most difficult to mange for the natural medicine
practitioner. Certain nutrients and herbs can adversely
affect the bioavailability and utilisation of certain drugs.
The most common interactions are:
- Inhibiting the absorption of the drug - e.g. supplements
containing soluble fibre, such as pectin or oat bran,
may impair the intestinal uptake of the anti-cholesterol
drug lovostatin.
- Inhibiting the bioavailability of the drug - iron supplements
can impair the bioavailability of several common drugs
such as carbidopa (an anti-convulsant), tetracycline (antibiotic),
thyroxine and captopril.
- Enhancing the bioavailability of the drug-e.g. it is
thought that more than 1g of vitamin C per day may enhance
the bioavailability of oestrogen replacement drugs.
- Inhibiting or modifying the drugs’ ability to
carry out its primary function - e.g. taking high dose
vitamin B6 with the anti-convulsant levadopa can lead
to increased peripheral levels of the drug, while reducing
the amount that enters the brain (thus reducing clinical
effectiveness).
- Enhancement of drug action - e.g. taking high doses
of nutritional or herbal anticoagulants along with the
anticoagulant drug warfarin may lead to significantly
extended bleeding time and a higher risk of haemorrhage.
The examples of potential drug amplification by supplements
are too numerous to cover but just a short list of examples
relating to amplification of cardiovascular drugs should
give a idea of just how common an occurrence such interactions
can be:
Coenzyme Q10:
anti-hypertensive, anti-angina and anti-arrhythmic drugs
Magnesium:
anti-hypertensive, anti-angina, anti-arrhythmic and anti-coagulant
drugs
Potassium:
anti-hypertensive, anti-angina and ant-arrhythmic drugs
Vitamin E:
anti-coagulant and anti-arrhythmic drugs
Omega 3 fish oils:
anti-coagulant and lipid-lowering drugs
Hawthorn berry:
Anti-hypertensive, anti-angina and anti-arrhythmic drugs
Cayenne:
anti-coagulant drugs
Garlic:
anti-coagulant, lipid-lowering and anti-hypertensive drugs
Ginkgo biloba:
anticonvulsant drugs
Terrass, S.
NUTRIT. PRACT. 1999, 1 (3) 32-4
SURGERY PATIENTS AT RISK FOR HERB-ANAESTHESIA INTERACTIONS
The use of herbal medicines and nutraceuticals among patients
about to have surgery is becoming more widespread, yet most
patients do not tell their physicians. In one study 979
patients who were about to have surgery were asked about
their use of herbal remedies and nutraceuticals (supplements
not derived from plants). One hundred and seventy (17.4%)
patients reported taking such products. The most often used
herbs were ginkgo biloba (32.4%), ginseng (26.5%), and garlic
(26.5%). Patients are recommended to stop taking herbal
preparations at least 2 weeks before elective surgery. Warning
about possible side-effects are given for the following
herbal remedies:
Ephedra: May interact with antidepressants
or antihypertensives to cause increases in blood pressure
or heart rate.
Feverfew: May increase bleeding, especially
in patients already taking anticoagulants.
Ginkgo: Side effects as feverfew.
Garlic: Side effects as feverfew.
Ginseng: May decrease effectiveness of
some anticoagulants; use associated with hypertension, tachycardia,
bleeding.
Kava-kava: May increase effects of some
anti-seizure medications or prolong effects of some anaesthetics.
St John’s Wort: May prolong effects
of some narcotics and anaesthetics.
Larkin, M
LANCET 2000, 354 (9187) 1362
