Traditional and modern medicine have much to offer each other despite their differences. Priya Shetty assesses an uneasy relationship.
Traditional medicine (TM) is due a revival. For millennia, people around the world have healed the sick with herbal or animal-derived remedies, handed down through generations.
In Africa and Asia, 80 per cent of the population still uses traditional remedies rather than modern medicine for primary healthcare.
And in developed nations, TM is rapidly gaining appeal. Estimates suggest up to 80 per cent of the population has tried a therapy such as acupuncture or homeopathy. And a survey conducted earlier this year found that 74 per cent of US medical students believe that Western medicine would benefit by integrating traditional or alternative therapies and practices. 
The industry is worth big money. In 2005, traditional medicines worth US$14 billion were sold in China. And in 2007, Brazil saw revenues of US$160 million from traditional therapies part of a global market of more than US$60 billion. [2, 3]
The truth is that modern medicine is desperately short of new treatments. It takes years for a new drug to get through the research and development pipeline to manufacture and the cost is enormous.
And growing drug resistance, in part caused by the misuse of medications, has rendered several antibiotics and other life-saving drugs useless.
Both these trends mean that scientists and pharmaceutical companies are urgently looking for new drug sources and are increasingly turning their eyes to traditional medicine.
A few major triumphs have stoked interest in traditional medicine as a source for highly successful and lucrative drugs. The best known of these is artemisinin used to treat malaria (see Box 1).
What it is for
Originally used in
Foods such as oyster mushrooms and red yeast rice.
Used to synthesize other compounds such as mevastatin and pravastatin
Vinca alkaloids (vincristine, vinblastine)
But making traditional medicine truly mainstream incorporating its knowledge into modern healthcare and ensuring it meets modern safety and efficacy standards is no easy task and is far from complete.
And there is rising concern among conservationists that a growing traditional medicine market threatens biodiversity through overharvesting of medicinal plants or increased use of body parts from endangered animals, such as tigers, rhinos and elephants.
Beyond the sustainability of natural resources, marrying traditional and modern medicine faces numerous challenges that stem from key differences in how each is practiced, evaluated and managed (see Table 2).
Protection and piracy
One of the most striking differences between traditional and modern medicines is the legal protection given to knowledge.Traditional practitioners have historically shared their knowledge and experience freely defining open-access before the term even existed. Modern medicine, on the other hand, has stringent intellectual property laws and a highly evolved patenting system used to protect knowledge about drugs or medical techniques.
As Western researchers realise the wealth of knowledge stored in traditional medicine systems, and the need for new drugs becomes more urgent, many scientists have begun searching indigenous sources for new drugs: a term dubbed bioprospecting (see Bioprospecting).
In some cases, researchers have sought patent protection for medicinal compounds that had already been used for centuries to treat disease. An example is the 1995 patent on an anti-fungal neem derivative commonly used in Indian traditional remedies. The European Patent Office (EPO) granted a patent to the US Department of Agriculture (USDA) and the multinational WR Grace and Company.
The Indian government convinced the EPO to revoke the patent on the basis of prior use, but it took five years and millions of dollars.
This plundering of freely available indigenous resources has been termed biopiracy and is a strong example of the challenges facing efforts to take traditional medicine mainstream.
Some regions have tried to tackle the problem by enacting laws to protect indigenous knowledge. For example, Cusco, in Peru, last year outlawed the exploitation of native species for commercial gain, including patenting genes or other resources the trees contain (see Peruvian region outlaws biopiracy).
Indias Council for Scientific and Industrial Research (CSIR) takes a more pragmatic approach to bridging the divide. In 2001, it launched a traditional knowledge digital library (TKDL). From last year, the EPO has been able to consult the 24 million page, multilingual database on traditional remedies and medicinal plants before granting patents (see BioMed Analysis: Keep traditional knowledge open but safe).
Many other countries have, or are considering establishing, similar databases to protect their local resources, including China, Ghana, Malaysia, Nigeria, South Africa, Tanzania, Thailand and some nations in the Middle East.
Beyond differences in indigenous and Western knowledge systems, efforts to make traditional medicines mainstream also have to cope with significant differences in regulation.
Every country has a national drug authority of sorts, responsible for administering and managing modern medicines and setting drug policies.
The problem with traditional medicine is that it often means different things to different people. A single medicinal plant may be classified as a food, a dietary supplement or a herbal medicine, depending on where you are.
A 2005 survey of WHO member states found that 8490 countries (around 60 per cent) had no national policy, laws or regulations for traditional medicine (although more than half of these proposed developing them) . These are often the countries where traditional remedies are used the most (see Figure 1).
And those countries with TM legislation take diverse approaches to licensing, dispensing, manufacturing and trading traditional remedies.
The lack of regulation means there are just as many fake remedies and false practitioners as there are genuine treatments. And that can have fatal results. For example, last year, two people died and nine were hospitalised after taking fake anti-diabetic traditional medicine, used to lower blood sugar, in the Xinjiang Uygur Autonomous Region in China. 
For most of the past decade, the WHO has been working to develop international guidelines and technical standards to help countries formulate policy and regulations to control traditional medicines.
If regulation of traditional and Western medicines varies, so too do methods for evaluating and testing them.
Modern drugs go through a rigorous series of laboratory tests and clinical trials before coming to market. Modern medicine has developed powerful methods for proving effectiveness, testing for safety and standardising good manufacturing practices.
In contrast, few scientific tests are done to evaluate traditional medicine products and practices. Quality tests and production standards tend to be less rigorous or controlled and in many cases, practitioners may not be certified or licensed.
Of course, some researchers believe that putting a drug that has been tried and tested in thousands of people for decades or centuries through the same hoops as a brand new chemical is not appropriate.
But many agree that before a traditional medicine can be imported into a conventional framework of pharmaceuticals, it will require reassessment.
In some cases, this means adapting standard methods to cope with ethical issues that do not arise with conventional drug development. US researchers Jon Tilburt and Ted Kaptchuk have, for example, suggested that clinical trials of traditional medicines must follow different rules for research ethics (see Box 2). 
Box 2: Rules of research ethics for clinical trials of traditional medicines*
1. Justifiable social need for the research
The rationale for testing a traditional medicine in a clinical trial cannot simply be that it already exists as a treatment. There must be both a social need and some preliminary evidence that the medicine will not negatively counteract other medicines used to treat the same disease. Different stakeholders will define social need in different ways for example, a government may want to prevent any other party from commercialising the treatment and health campaigners may want the clinical trial to try to produce better drugs.
2. Appropriate definitions of inclusion and exclusion criteria, and outcome measures
Concepts of health and sickness differ between modern and traditional medicine. For example, Western researchers would probably categorise heart failure in patients according to the New York Heart Association classification. But practitioners of traditional Chinese medicine (TCM) would see heart failure as a heart yang chi deficiency or a kidney yang deficiency, categorising patients based on pulse or tongue examination. Researchers testing a herbal remedy for heart failure would need to take both biomedical and TCM criteria into account for the results to be valid from both perspectives.
3. Innovative protocol design
Drugs brought to market by putting traditional medicines through clinical trials must be rigorously tested but researchers will need to think carefully about how best to design their protocol. Standard methodologies may not be appropriate for a medicine that contains a mixture of active ingredients or in treatments that vary between practitioners. But adaptations of standard protocols could accommodate many of these issues. For example, cluster randomised controlled trials could be rigorous while allowing for practitioner variability.
4. Establishing standards for safety and evidence
The familiarity of traditional medicines, and their widespread use, could bias some researchers towards a good safety profile. Care is needed early on to determine safety requirements.
*Derived from an ethical analysis by Jon Tilburt and Ted Kaptchuk. 
Ethical issues aside, it can be extremely difficult to apply modern methods developed to test standardised drugs to the inherently diverse range of products that are traditional medicines.
Many traditional medicines are made by crushing the leaves or bark of plants and trees, and the resulting mixture can contain hundreds of potentially active molecules. Identifying these is hard enough testing each one for safety and effectiveness is practically impossible.
And unlike many modern pharmaceuticals, the quality of source material for traditional medicines varies greatly, even within individual countries. This is true both because of differences in the genetic material used as well as other variable factors such as environmental conditions, harvesting, transport and storage.
Dosage is similarly varied. Modern medicine demands standard dosages that tend to vary only with bodyweight or severity of disease. Traditional healers are more likely to give their patients a unique dosage or combination of medicines that is concocted only during the consultation and based on the patients symptoms.
Poor evaluation results may therefore be the result of any number of factors from the mistaken use of the wrong species of plant to contamination with toxic substances during storage to overdosage. They do not necessarily indicate that the medicine is an inappropriate candidate for modern drug development.
Similarly, if a traditional medicine is deemed clinically ineffective by modern standards, it doesnt mean it cannot work as a therapy. Homeopathy, for example, seems to work despite hundreds of clinical trials suggesting that it has no biological effect. Many scientists believe this is a placebo effect generated because homeopathy practitioners spend far longer listening to what their patient has to say than do conventional doctors. 
But while the placebo effect can certainly be beneficial, many would consider it unethical to prescribe clinically ineffective treatment in order to induce this benefit.
Then there is the issue of combining traditional medicines and modern drugs. The belief system that accompanies traditional medicine can sometimes interfere with modern treatments. In 2009, Kumanan Wilson, of the University of Toronto, Ontario, Canada, and colleagues reviewed barriers to malaria treatment in Africa in the journal BMC International Health and Human Rights. 
In Africa alone, malaria is estimated to kill one million people, more than 90 per cent of whom are children under five. Wilsons team found that a reliance on traditional medicines and linked cultural beliefs such as the idea that a child with convulsions is possessed or haunted by spirits and would die if taken to hospital was a major barrier to effective treatment for malaria.
In many of the studies the team reviewed, respondents said that traditional therapies such as herbal remedies were used as a first-line treatment before modern drugs.
New techniques for old treatments
New scientific techniques are also being applied to traditional medicine in the search for modern drugs. These innovative approaches are developing at breakneck speed (see Table 3).
Researchers start with the end product, a clinically useful compound for example, and work backwards to find out what it contains and how it functions. This can offer clues about how particular medicines work, and where they act in the body.
This advanced screening relies on high-speed data processing and sensitive detectors to conduct millions of biochemical, genetic or pharmacological tests in a few minutes. The process can quickly identify active compounds that affect particular biological pathways.
The systematic study of how specific ethnic groups use medicinal plants.
This holistic approach aims to understanding the way different chemicals and metabolic processes interact within the body. Since traditional medicines often have numerous active ingredients, it could be used to measure the whole bodys response to the mixture of compounds.
Table 3: How to create modern drugs from traditional compounds 
In India, the CSIR has teamed up with several public and private partners to conduct clinical trials on herbal products generated through reverse pharmacology. It says this has resulted in wider acceptance of Ayurvedic traditional medicines and promises cheaper, faster and more effective drugs. 
And in Africa, at the Kenya Medical Research Institute, scientists at the institutes Centre for Traditional Medicine and Drug Research are testing thousands of plants in the hope of finding a new antimalarial (see Turning plants into pills in Kenya). The team has had a handful of promising leads, though none has yet been effective enough to pursue as a candidate drug.
Integrating traditional medicine into modern healthcare is certainly being taken seriously by some of the biggest research bodies worldwide. In 2007, 62 countries had national institutes for traditional medicine up from 12 in 1970. 
The US National Institutes of Health, for example, houses an organisation called the National Center for Complementary and Alternative Medicine (NCCAM), which this year has a budget of US$128.8 million.
NCCAM funds research into how acupuncture, herbal supplements, meditation, or osteopathy can help treat conditions such as cancer, cardiovascular disease, and neurological disorders.
Developing countries with ancient histories of traditional medicine are also hunting for ways to modernise their own medical heritage. In China, modern and traditional medicine are practiced alongside each other at every level of the healthcare system. The government gives equal weight to developing both and China has a large and active research community on integrative medicine.
In Latin America too, several countries are working to provide modern and traditional health care side-by-side (see Modernising traditional medicine must work for locals).
African governments, including those of Ghana and Nigeria, are rolling out educational campaigns and launching anti-counterfeiting technologies to better monitor drug procurement. And initiatives such as the African Network for Drugs and Diagnostics and Innovation are encouraging the mining of traditional medicine.
So traditional medicine has much to offer global health, especially as new drugs have never been more urgently needed. If both developed and developing countries joined research capacities in equitable collaborations, new scientific techniques could spark a revival in global health research and development.
 Abbott, R. B. et al. Medical student attitudes toward complementary, alternative and integrative medicine Evidence-based Complementary and Alternative Medicine (2010)
 WHO factsheet on traditional medicine. WHO (2008)
 WHO Country Cooperation Strategy 2006–2011, India: Supplement on traditional medicine WHO Country Office for India, New Delhi (2007)
 Ghalib, H. The hunt for the next Artemisinin TDR News (2007)
Deadly counterfeit diabetes drug found outside China's Xinjiang Xinhua News (2009)
 Tilburt, J.C. and Kaptchuk, T.J. Herbal medicine research and global health: an ethical analysis Bulletin of the World Health Organization 86 577–656 (2008).
 Ernst, E. Homeopathy: what does the "best" evidence tell us? The Medical Journal of Australia 192 458–60 (2010).
 Maslove, D.M. et al. Barriers to the effective treatment and prevention of malaria in Africa: A systematic review of qualitative studies BMC International Health and Human Rights 9 26 (2009)
 Patwardhan, B. Drug discovery and development: Traditional medcine and ethnopharmacology perspectives SciTopics (2009)
 Potential of traditional medicine should be fostered, Economic and Social Council President tells panel on attaining Millennium Development Goals in public health. UN Economic and Social Council (2009)