Herbal therapies, taken for medicinal and health reasons, are becoming increasingly popular and are often regarded as innately safe. But their interaction with other medicines is less well known – and could be dangerous.
One fifth of patients on prescription medication also use herbal remedies, high dose dietary supplements or both, according to the South African Journal of Anaesthesia and Analgesia. When herbal medicines sold by traditional healers are included, that figure shoots up to 80%.
Herbal therapies are plant-derived products. They have been part of human existence since the beginning of time and span the spectrum from home-brewed teas prepared from collected leaves and herbs to products with official approved status granted by drug-regulating authorities.
The danger of herbal medicines lies in the widespread perception that because they are “natural”, they are safe. This perception is ill informed. The manufacture of herbal medicine is poorly regulated in South Africa. This means the true content of different preparations vary greatly between manufacturers. Some tend to under-report or omit the side effects of their therapies and overemphasise the positive effects.
How it can be bad for you
How herbal medicines and conventional drugs interact is not fully understood. For patients who fail to disclose using herbal medicines before they go into surgery, the side effects can be dire. Among the most dangerous adverse effects are increased bleeding and resultant blood loss throughout the surgery.
Research from the New England Journal of Medicine shows that 70% of patients don’t tell the doctors and physicians treating them that they are using any of these drugs.
A survey looking at the increased surgical risk from herbal products found up to 51% of surgical patients used herbal medicine in the two weeks before a procedure. Of the drugs patients used, 27% altered clotting, 30% had a direct influence on heart rhythm, rate and blood pressure and 20% increased sedation.
These are the three most high risk problems during operations and could result in complications - or even death.
Numerous research publications have shown that these could have serious implications if they are used with other medication.
For instance, when used in clinically effective doses, garlic’s interaction with oral contraceptives may result in contraceptive failure. Ginger can cause decreased blood pressure, exaggerating the effects of blood pressure medication and interfering with blood pressure therapy.
And although wounds are often treated with kava, its side effects include anxiety, insomnia, restlessness, muscle pain and headaches, drowsiness and depression of motor reflexes. This may be the result of kava interacting with the central nervous system depressants such as sedatives and tranquilisers or alcohol.
When evening primrose oil interacts with anaesthetics, it could increase the risk of seizures during or after an operation. And when ginger, evening primrose oil or gingko interact with medicine to prevent the blood from clotting these interactions could increase the risk of bleeding.
At the South African Society of Anaesthesiologists, we have anecdotal evidence of patients not disclosing their use of herbal medicines such as omega oils, arnica tablets, evening primrose oil and St. John’s wort. In most instances it meant the physicians had to return to theatre because their patients' excessive bleeding.
The science behind it
Some physicians may not be familiar with all the clinical effects of the herbal medication or the action of a specific herb and would therefore underestimate the risk it poses to their patient.
The bioactive components contained in a single herb may contribute, in varying degrees, to the observed effect and interaction, leading to difficulties in predicting and explaining herb-drug interactions.
Other herbal medicines compete for the same cytochrome pathway as anaesthetic agents commonly used, which may slow down the clearance of the anaesthetic drug administered, predisposing patients to toxic effect as a result of higher plasma concentration. The net effect of such interactions is pharmacological chaos and unexpected drug toxicity.
Most medical authorities agree that the use of herbal supplements and medicines should be stopped at least two weeks before surgery.
Perhaps you, like many others, take herbal medicines because you believe it’s the smart thing to do. In some cases it may well be so. But to tell your healthcare practitioner that you use such therapies, especially in run-up to and after a surgical procedure, may be one of the smartest things you ever do.
Tinus Dippenaar does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.
Authors: The Conversation