Herbal medicine and the Cat Unit

Read "African genesis: A pharmacopoeia for Africa" from The Economist October 5th 2006. (Subscription required.)

The Association for African Medicinal Plants Standards, a collaboration of medicinal-plant scientists from 14 countries, plans to launch an African Herbal Pharmacopoeia.

In Phase One, 23 herbal profiles have been completed. Phase Two will include the preparation of a further thirty herbal profiles to make a total of 53 available for use by farmers, traders, scientists and government health regulators throughout Africa and by importers from the rest of the world.......AAMPS will ensure maximum access to these standards and aim to prepare an interactive database and web site as well as publish CD-ROM and print versions of the profiles. (AAMPS website)

According to the World Health Organization, the global market for medicinal plants exceeds $60 billion a year. IMS reports that "in 2005 total global pharmaceutical sales passed another threshold to reach $602 billion. However, a large number of manufactured pharmaceuticals are based on plant extracts or are chemically manufactured versions of molecules first extracted from plants (about one-third, I believe, last time I looked.) Thus phyto-pharma-chemistry is an important area for research and development. Indeed it is one that is financially supported by the pharmaceutical industry and the U.S. National Institutes of Health.

I welcome the initiative of the 28 scientists to develop an African herbal pharmacopia.

I am also concerned that it be done well. Plants have evolved many protections to keep from being eaten by insects and animals, and many will make you very sick indeed if you eat them. As in any medicine, one has to be careful that the benefits likely to derive from taking a herbal medicine outweigh the risks involved. Regulations have been created for the licensing of ethical pharmaceuticals that require firms to conduct extensive tests of safety, efficacy and effectiveness to assure that the benefits and risks of manufactured drugs are known. A huge effort goes into training those who prescribe and distribute ethical pharmaceuticals to assure that they adequately understand these risks and benefits and can council their patients on their appropriate uses.

In Africa, I suspect that there is a lot of misprescription of herbal medicines now, but at least the traditional knowledge systems should have evolved some safeguards against the worst problems. Making herbal remedies from one part of Africa available in other parts of Africa may not involve even that protection, much less the protections of the modern medical system has evolved for ethical pharmaceuticals. I hope that the African Herbal Pharmacopia does include the appropriate information about risks as well as putative benefits.

There are significant individual differences in reaction to plants. Food allergies illustrate that a plant that is good food for one person may be allergenic to another. Thus G6PD deficiency, which can make a person allergic to faba beans, peas and lentils and is quite common in some African populations (up to 20 percent of the population), carries with it known sensitivities to many pharmaceuticals. A herbal medicine might be quite safe in South Africa, and dangerous to peoples in the Sahel, or quite safe in West Africa but dangerous to peoples in East Africa.

While a great deal of effort goes into producing pharmaceutical chemicals of constant quality, and in the development of standards for pharmaceuticals, plants are inescapably more varied in their chemical contents. Not only does the genome of the individual plant matter, but also the conditions under which it was grown. It can matter what the soil characteristics were, whether it was grown on the sunny or shady side of a hill, how much rain fell, etc. So the safety and efficacy of one herbal preparation may be quite different than that of the same herbal preparation grown in other locations. In practice it apparently is quite difficult to define standards for biological products, and it is certainly beyond the capabilities of the African traditional practitioners prescribing herbal medicines to do chemical testing of the levels of active ingredients in those products.

Which brings me to the Cat Unit.

the dose of a drug (per kilogram of body weight of cat), which is just large enough to kill a cat when administered intravenously; was applied in the standardization of digitalis materials.

Digitalis is an important medicine, and was in the pharmacopia 200 years ago. The druggists 100 years ago sold it as an extract of the foxglove plant. But it is a very powerful drug, and all the variations mentioned above affect its concentration in the plant. So the drug store owner, who often grew the foxglove or obtained it from a local garden, had the problem of how to determine the right dosage of the concoction he distilled.

Thus the cats. Dog units could have been used, but there would have been more upset neighbors had the drug store owners picked up stray dogs for testing than they got with stray cats. Drug stores regularly had caged cats in the back for standardizing the new batches of digitalis.

This may sound strange, but hundreds of papers were published on the standardization of digitalis by means of cat units. It was a practical, if not politically correct, solution to a real problem of safety and efficacy -- too much digitalis was fatal to the patient, and too little did no good.

Will the African Herbal Pharmacopia provide an affordable, practicable means of standardization of the herbal products it recommends? Will the practitioners, such as the gentleman pictured above, be trained in the use of those means?