Importance of plants in modern pharmacy and medicine
Types of drugs derived from plants
Herbal drugs derived from specific parts of a medicinal plant
• the herb of St John’s wort (Hypericum perforatum), used in the treatment of mild to moderate depression
• the leaves of Ginkgo biloba, used for cognitive deficiencies (often in the elderly), including impairment of memory and affective symptoms such as anxiety
Natural products or compounds isolated from nature
Use of herbal medicines
The use of these remedies is extensive,
increasing and complex. In several surveys 20–33% of the UK population
claimed to regularly use CAM alone or in addition to orthodox or
conventional medicine and treatments. In the UK, usage is particularly
frequent amongst those who are over-the-counter medicines-users. There
is not, on the whole, a wide understanding of what herbal medicines are
(or are not) (IPSOS-MORI 2008).
Healthcare professionals and students also commonly use such products.
Forty-three percent of students at a University School of Pharmacy
reported using at least one type of CAM during the last 12 months (Freymann et al 2006).
In the United States, approximately 38% of adults and approximately 12% of children are using some form of CAM (NIH/NCCAM). Kennedy et al (2008)
showed that in the preceding 12 months about 38 million adults in the
US (18.9% of the population) used herbal medicines or supplements, but
that only one-third revealed this use to their physician. Data for other
regions are even more limited, but the usage of herbal medicines is
widespread in countries like India, Indonesia, Australia and China, to
name just a few.
In developed countries, most
purchases of HMPs are made on a self-selection basis from pharmacies and
health-food stores, as well as from supermarkets, by mail order and via
the Internet. Normally, with the exception of pharmacists,
there is no requirement for a trained healthcare professional to be
available on the premises to provide information and advice. In
any case, most HMPs can be sold or supplied without the involvement of a
healthcare professional and several studies have confirmed that many
individuals do not seek professional advice before purchasing or using
such products, even when purchased from a pharmacy (Barnes et al 1998, Gulian et al 2002).
Rather, consumers of HMPs tend to rely on their own (usually limited)
knowledge, or are guided by advice from friends and relatives or the
popular media. Consumers who do seek professional advice (e.g. from
their pharmacist or general practitioner) may find that he or she is not
able to answer their question(s) fully. In some cases this may be
because the information simply is not available, but it is also
recognized that, at present, many healthcare professionals are not
adequately informed about herbal medicines, particularly with regard to
their quality, safety and efficacy. This book attempts to redress that
omission.
HMPs are used for general health
maintenance, as well as for treating diseases, including serious
conditions such as cancer, HIV/AIDS, multiple sclerosis, asthma,
rheumatoid arthritis and osteoarthritis. Older patients, pregnant and
breastfeeding women, and children also take HMPs, and this raises
concerns because, as with conventional medicines, precautions need to be
taken. For example, few medicines (whether conventional or herbal) have
been established as safe for use during pregnancy and it is generally
accepted that no medicine should be taken during pregnancy unless the
benefit to the mother or fetus outweighs any possible risk to the fetus.
Similarly, HMPs should be used with caution in children and the
elderly, who, as with conventional medicines, differ from adults in
their response to, and metabolism and clearance of drugs. The use of
herbal medicines by patients who are already taking prescribed medicines
is of particular concern as there is the potential for drug–herb
interactions to occur. For example, important pharmacokinetic and
pharmacodynamic interactions between St John’s wort (Hypericum perforatum) and certain conventional medicines have been documented (Williamson et al 2009