Herbal medicines: what risks do they pose?

A review published in today’s Medical Journal of Australia has taken aim at herbal medicines and their possible contribution to morbidity and mortality

The narrative review by researchers at the University of Adelaide, Murdoch University and Curtin University has highlighted issues with the medicines, including lack of tight control of quality and content, as well as interactions with prescription and other medications.

They found that some traditional herbal preparations contain toxic chemicals from both animals and plants, as well as heavy metals and pesticides.

“Toxic side effects of herbal medicines used in traditional societies have typically not been reported, and this is often cited in favour of their safety,” says lead author Professor Roger Byard, Professor of Pathology at the University of Adelaide.

“However, the lack of systematic observation has meant that even serious adverse reactions, such as the kidney failure and liver damage caused by some plant species, have gone unrecognised until recently.”

The review points out that more than half of those who use complementary medicines – including those using herbal products – did not inform their doctors.

This was for several reasons, including the ongoing perception that herbal preparations are “natural” products that can be freely combined with pharmaceutical drugs.

The authors say problems with CMs include:

  • Adulteration with pharmaceutical agents: pharmaceuticals that have been detected in ostensibly herbal products include phenytoin, antibiotics, antihistamines, corticosteroids, aminopyrine, aspirin, bromhexine, chlordiazepoxide, diazepam, diclofenac, glibenclamide, hydrochlorothiazide, indomethacin, mefenamic acid, paracetamol, phenacetin, phenylbutazone, and theophylline;
  • Substituted plant species, which the authors say may be deliberate if the original plant is difficult or expensive to obtain; herbal substitution can also be inadvertent if there has been misinterpretation or inaccurate transcribing of the names or formulae in texts;
  • Presence of toxic substances;
  • Inadequate processing that might not ensure the removal of unwanted components that can cause adverse events: for example, dried aconite root must be soaked in water and boiled before it is safe to use; and
  • Pharmaceutical interactions, described as “a major area of concern”.

“It is likely that the majority of adverse drug reactions and drug interactions associated with alternative medicines are unreported,” the authors write.

“The examples we have discussed in this article indicate that some herbal products should carry clear warnings, and highlight the need for a more open debate about claims regarding their efficacy and risks.”

“We feel it would be appropriate for the Therapeutic Goods Administration to require manufacturers to have samples independently tested before placing them on the market,” says Professor Byard.

“Legal action should be considered in cases of non-compliance with applicable regulations, and preparations containing illegal substances should be banned.”

The review points out that most herbal medicines are listed (AUST L) rather than registered (AUST R) and thus their listing on the ARTG is based on self-assessment, “a system that relies on the honesty of the manufacturer with regard to their composition.

“TGA audits during 2013 and 2014 found that 6–7% of complementary medicines did not comply with regulations regarding formulation, manufacturing or quality.

“With more than one in 20 complementary medicines failing essential composition quality control in Australia, it is clear that more meaningful regulation of the sector is needed.”

Complementary Medicines Australia has hit back at the study, saying that Australian consumers can be confident in herbal products purchased in Australia.

“Australia has some of the most stringent regulations in the world for herbal products, as for all complementary medicines on the Australian market,” says its CEO, Carl Gibson.

“Products are required to be entered onto the Australian Register of Therapeutic Goods which is maintained by the regulator, the Therapeutic Goods Administration.

“Unless entered on the ARTG, these products cannot be legally imported, exported, manufactured, or supplied to consumers in Australia.”

“Products that are medicinal in nature but not listed on the ARTG may not have been made under GMP principles, and may not meet the quality and safety standards expected by Australian consumers.

“Concerns raised by the authors, such as adulteration with pharmaceutical agents, inadequate processing and the presence of toxic substances, have been known to affect products purchased online from overseas, which are not subject to the same regulations as those enforced in Australia.”

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