Toxicity herbal drugs

The single dose of a drug is mo.stly derived from experience it is only possible in a very few cases to calculate it from the activity of the constituents. However, as many herbal drugs arc only weakly active and contain non-toxic substances, i.e, the therapeutic index is large, exceeding the dose is usually only of minor significance nevertheless, the pharmacist must know what the exceptions are in this book, the sections on Side effects and Making the tea draw particular attention to such cases, c.g. arnica flowers, liquorice root, etc. 

Keywords Alangium salvifolium, Sub chronic toxicity studies, herbal drugs... 

All drugs, even conventional drugs, may cause toxic side effects in some people, and herbal drugs are no... 

For each herbal drug preparation, a comprehensive specification must be submitted. This must be established on the basis of recent scientific data and must give particulars of the characteristics, identification tests, and purity tests. This has to be done, for example, by the appropriate chromatographic methods. If deemed necessary by the results of the analysis of the starting material, tests on microbiological quality, residues of pesticides, fumigation agents, solvents, and toxic metals have to be carried out. Radioactivity should be tested if there are reasons for concerns. Quantitative determination (assay) of markers or of substances with known therapeutic activity is required. The content must be indicated with the lowest possible tolerance. The test methods must be described in detail. 

Ma huang (ephedra) is commonly found in herbal weight loss products that are often referred to herbal fen-phen. Some weight loss clinics and herbal outlets promote Herbal fen-phen as an alternative to fenfluramine, the prescription drug that has been withdrawn from the market due to toxicity. Herbal fen-phen products sometimes contain St John s wort and are sold as herbal prozac . Ephedra-containing products are also marketed as decongestants, bronchodilators and stimulants. Other promoted uses include bodybuilding and enhancement... 

Furuya, T. 1957. Pharmacological action, including toxicity and excretion of berberine hydrochloride and its oxidation product. Bull. Osaka Med. School 3 62-67. Cited in De Smet, P.A.G.M. 1992. Adverse effects of herbal drugs. Volume 1. New York Springer. 

Batchelor, W.B., J. Heathcole, and I.R. Wanless. 1995. Chaparral-induced hepatic injury. Am.. Gastroenterol. 90(5) 831-833. Clark, F., and R. Reed. 1992. Chaparral-induced toxic hepatitis California and Texas, 1992. /. Am. Med. Assoc. 268 3295-3298. De Smet, RA.G.M. 1993. Adverse effects of herbal drugs, Volume 2. Berlin Springer. 

Quality-related problems are mostly associated with unregulated herbal drugs and include the (deliberate) inclusion of prohibited or restricted substances (e.g. admixture of synthetic actives, adulteration with toxic plants), contamination with toxic substances (e.g. heavy metals, residues) and incorrect declaration of constituents and content on the packaging labels. 

Adulteration, which can be accidental or deliberate, is another problem. Many herbal products have been found to contain prescription or OTC drugs and dangerous heavy metals. In 1998, for example, the California Department of Health reported that 32% of Asian herbal medicines sold in that state contained undeclared pharmaceuticals or heavy metals. A subsequent study of more than 500 Chinese herbal medicines found that about 10% of them contained undeclared drugs or toxic levels of metals. The FDA and other investigators have also detected sildenafil, colchicine, adrenal steroids, alprazolam, and other prescription drug ingredients in products claimed to contain only natural ingredients. 

In many developing countries of the world, there is still a major reliance on crude drug preparation of plants used in traditional medicines for their primary health care. Pharmacognosists employed in the different institutions are aware of the changing trends of herbal medications and a number of useful texts on the analysis, uses, and potential toxicities of herbal remedies have appeared recently, which serves as useful guides in pharmacy practice. The history of medicine includes many ludicrous therapies. Nevertheless, ancient wisdom has been the basis of modem medicine and will remain as one important source of future medicine and therapeutics. The future of natural products drug discovery will be more holistic, personahzed and involve the wise use of ancient and modem therapeutic skills in a complementary manner so that maximum benefits can be accmed to the patients and the community. 

We are exposed to plant products (many of the earlier drugs and most of the herbal pharmacopoeia in use today are crude plant extracts), some of which are potentially toxic, as, less commonly, are foods of animal origin. Medicinal drugs are just one of a set of chemicals which are exposed to the range of defence mechanisms put up by the body to protect it from the onslaught of foreign chemicals. 

Detractors of herbal medicine use have legitimate concerns about dosage variability, possible toxicity and adulteration, herb-drug interactions, and above all, lack of FDA regulation. Far from being intrinsically harmless, many pharmacologically active plant alkaloids and other compounds are natural defensive poisons their very effectiveness may be an unanticipated consequence of their adaptive toxicity to grazing animals and... 

Clark, F., and D. R. Reed. Chaparral-induced toxic hepatitis. California and Texas, 1992. MMWR Morbid Mortal Wkly Rep 1992 41(43) 812-814. Anon. From the Food and Drug Administration. Public Warning about herbal product Chaparral . J Amer Med Ass 1993 269(3) 328. 

However, the information derived from a detailed pharmacokinetic study will help to anticipate potential botanical product-drug interactions, to optimize the bioavailability, the quality, and hence the efficacy of herbal medicines, to support evidence for the synergistic nature of herbal medicines, and to better appreciate the safety and toxicity of the plant. Because pharmacokinetic studies with herbal medicines are often complicated by their chemical complexity and by the fact that the active compounds are often unknown, it could be one future issue to assess bioavailability by measuring surrogate parameters in plasma or tissue instead of directly assaying putative active compounds in the blood. In summary, to use HMPs in an evidence-based approach and to achieve the status rational phytomedicine, more experimental studies are needed to characterize the bioavailability and pharmacokinetics of botanical products. 

Chapter 62 Drugs Used in the Treatment of Gastrointestinal Diseases Chapter 63 Therapeutic Toxic Potential of Over-the-Counter Agents Chapter 64 Dietary Supplements Herbal Medications Chapter 65 Rational Prescribing Prescription Writing Chapter 66 Important Drug Interactions Their Mechanisms... 

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