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British Medical Journal 2003;327:881-882 (18 October)

Editorial

Herbal medicines put into context Their use entails risks, but probably
fewer than with synthetic drugs

Recent reviews have rightly alerted us to the risk associated with
herbal  medicines.1 This is necessary and important. But the more
important question  probably is-do the risks of herbal benefits outweigh
their potential for  harm? Therefore I will try to put herbal medicines
into context and consider  the benefit they might bring.

The potential benefits of herbal medicines could lie in their high
acceptance by patients, efficacy, relative safety, and relatively low
costs.  Patients worldwide seem to have adopted herbal medicines in a
major way.  Survey data from the United Kingdom show that herbal
medicine has been tried  by about 30% of the British population.2 The
associated out of pocket  expenditure was estimated to amount to £31m
(US$47.7m; ?45m) in the United  Kingdom2 and £1.3bn in Germany.3 Herbal
medicines are used predominantly for  minor and self limiting
indications, with respiratory tract infections  heading the list.3 But
even for those conditions the remarkable acceptance  of herbal medicines
can be a good thing only if they can be shown to do more  good than harm
at reasonable cost.

The efficacy of herbal medicines has been tested in hundreds of
clinical  trials, and it is wrong to say that they are all of inferior
methodological  quality. But this volume of data is still small
considering the multitude of  herbal medicines-worldwide several
thousand different plants are being used  for medicinal purposes.4 A
recent overview included 23 systematic reviews of  rigorous trials of
herbal medicines.5 Eleven came to a positive conclusion,  nine yielded
promising but not convincing results, and three were negative.  The
relative paucity of rigorous clinical trials is mostly due to the fact
that, compared with the pharmaceutical sector, the herbal industry is
small  and can rarely afford the considerable expense of a clinical
trial. Sadly  the traditional use directive, which sets out to harmonise
the registration  of herbal medicines in the European Union,6 lacks any
incentive for  companies to invest further into research. Public funds
are only very rarely  dedicated to research in this area.7

Even though herbal medicines are not devoid of risk,1 they could still
be  safer than synthetic drugs. Between 1968 and 1997, the World Health
Organization's monitoring centre collected 8985 reports of adverse
events  associated with herbal medicines from 55 countries.8 Although
this number  may seem impressively high, it amounts to only a tiny
fraction of adverse  events associated with conventional drugs held in
the same database.8  However, the relative paucity could also be due to
a relatively higher level  of underreporting. More conclusive evidence
on the relative risks of herbal  medicine versus synthetic drugs is
scarce. Linde et al showed that the  herbal antidepressant St John's
wort has only about half the rate of adverse  effects compared with
conventional antidepressants.9 Kava, an effective  herbal anxiolytic,10
has recently been banned in several countries,  including the United
Kingdom, because of the suspicion that, in rare cases,  it causes
hepatotoxicity. None the less, preliminary data indicate that it
probably is still safer than benzodiazepines.11 At present the relative
safety of herbal medicines is undefinable, but many of the existing
data  indicate that adverse events, particularly serious ones, occur
less often  than with prescription drugs.4

A further strength of herbal medicines is that they are inexpensive, at
least this is what the "herbal lobby" wants us to believe. The truth,
however, is that almost no conclusive cost evaluation studies are
available.12 Many, but by no means all, herbal medicines are inexpensive
to  buy; the potential for cost savings by using more herbal medicines
could  therefore be substantial-at present, however, we simply cannot be
sure.

Thus the evidence on herbal medicines is incomplete, complex, and
confusing.  They are certainly associated with both risks1 and
benefits.4 As more and  more people try herbal medicines, the pressure
increases on healthcare  professionals to be well informed about the
subject, and on researchers to  fill the many and somewhat embarrassing
gaps in our current knowledge.  Failing to do (and fund) this work
would, in my view, constitute the true  risk associated with herbal
medicines.

E Ernst, director

Complementary Medicine, Peninsula Medical School, Universities of Exeter
and  Plymouth, Exeter EX2 4NT (Edzard.Ernst@pms.ac.uk)

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Competing interests: EE's unit has received research fellowships from
herbal
manufacturers and retailers: Lichtwer UK, Pharmaton Switzerland, and
Boots
UK. Financial support for other research projects was also received from
Schwabe Germany and Novogen Australia.
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