Two people in San Francisco ended up in intensive care after taking a herbal remedy, it was reported last week. The incident is likely to raise questions about the safety of herbal medicines. But are they any more dangerous than the drugs dispensed by your doctor or those sold over the counter without a prescription?
It is a common belief that herbal medicines are safe and research suggests that they are used by at least a third of people in some countries, such as the UK.
To better understand the relative risks involved, it is helpful to put herbal medicines and pharmaceutical drugs into context. It is generally accepted that pharmaceuticals cause side effects. But, as part of licensing requirements, a risk-benefit analysis is undertaken to determine whether the benefits outweigh the potential harms. In other words, is the possible harm caused by the drug acceptable? If it is, the drug may be granted a marketing authorisation (product licence) by a regulatory authority, such as the Food and Drug Administration in the US or the European Medicines Agency in Europe.
Undeniably, pharmaceutical drugs kill people. In the US, it is estimated that pharmaceuticals kill around 100,000 people every year. For certain conditions, however, there may be no alternative to drug therapy and certain medicines can prolong life, such as drugs used to treat diabetes, heart disease and cancer.
By contrast, herbal medicines are considered by many to be a safer alternative and are preferred by a sizeable section of the public for treating non-life-threatening conditions. And there is some evidence to support the idea that herbal medicines are safer for minor ailments. For example, drugs to treat mild to moderate pain, such as paracetamol and aspirin, are known to cause side effects, including some that – although rare – can be serious, such as gastric bleeds. Whereas with herbal equivalents, such as devil’s claw, the risks of side effects are reportedly lower.
A tricky comparison
Adverse events associated with herbal remedies are reported far less often than those associated with pharmaceuticals. For example, in the UK, between 2006 and 2008, there were only 284 such reports for herbal medicines compared with 26,129 for pharmaceuticals in a similar two-year period.
The reasons for this vast difference are complex, and it has been suggested that adverse events of herbal medicines are unrecognised or underreported. Also, there are many more drugs consumed than herbal remedies so it is to be expected that the figures for pharmaceuticals are higher. However, the enormous difference does suggest that adverse events are far more common with pharmaceuticals than herbal remedies.
When serious side effects are triggered by herbal remedies it is often due to poor quality products, products containing newly discovered plant ingredients, or products that have been adulterated – including with pharmaceutical drugs.
For the public, buying herbal products that are regulated offers some assurance that the medicines are both safe and of acceptable quality. For instance, in the UK, traditional herbal remedies are manufactured to a high standard and include a patient information leaflet, which lists known side effects and, importantly, warns of possible interactions with pharmaceuticals, another cause of adverse reactions.
For example, St John’s wort – a herbal remedy used to treat mild depression – is known to have side effects when taken alongside fluoxetine (Prozac). The makers of these products also have a legal obligation to monitor any adverse reactions and report them to the regulators.
Another way to help avoid adverse reactions, especially when dealing with conditions that are not always suitable for self-treatment with over-the-counter drugs, is to visit a qualified herbalist. The training and regulation of herbalists varies widely from country to country and without government regulation of these practitioners, it is difficult for the public to assess who is legitimate.
However, voluntary regulation by professional associations does exist and is effective in many countries, including the US, Canada, the UK and Australia. This regulation helps to ensure that practitioners are appropriately educated and safe.
Herbal medicines are relatively safe compared with pharmaceuticals provided that they are regulated products or that they are prescribed by herbal practitioners who are registered with an appropriate governing body. But consumers need to be better informed about the dangers of obtaining herbs from unregulated sources if further cases of serious side effects are to be avoided.