Herbalists and laypersons have used herbs for centuries. Interest in and use of herbal products was revitalized in the late 1990s with the passage of the Dietary Supplement Health and Education Act, which allowed dietary supplements to be marketed without enduring the FDA-approval process required of drugs. Thus, despite the widespread use of herbal products, information about their safety and efficacy is generally sparse compared with the information available about prescription drugs. Toxicology and Clinical Pharmacology of Herbal Products was published in 2000 to help fill this information void. Since its publication, additional scientific information has come to light, and the public's interest in particular herbs has changed. Herbal Products: Toxicology and Clinical Pharmacology, Second Edition updates the information presented in Toxicology and Clinical Pharmacology of Herbal Products. Herbs were chosen for inclusion in the current volume based on their popularity, toxicity, and quantity and quality of information available. A companion volume, Dietary Supplements: Toxicology and Clinical Pharmacology, covers nonherbal dietary supplements.

The aim of this book is to present, in both comprehensive and summative formats, objective information on herbal supplements from the most reliable sources, with an emphasis on information not readily available elsewhere (i.e., detailed descriptions of case reports of adverse effects, pharmacokinetics, interactions, etc.). It is not designed to be a "prescribers handbook;" the intended audience is both forensic and health care professionals, particularly researchers and clinicians interested in more detailed or context-oriented clinical information than is available in most "herbal" or "natural product" references.

Although information about dietary supplements is widely available on the Internet, it is usually provided by product distributors, and is designed to sell products rather than to provide objective information about product efficacy and toxicity. Even reviews of dietary supplements in journals, newsletters, books, and electronic databases can be biased or incorrect. In compiling information to be included in Herbal Products: Toxicology and Clinical Pharmacology, Second Edition, emphasis was placed on the use of original studies published in reputable, peer-reviewed journals. Older studies, as well as more current literature, were utilized for completeness, with an emphasis on newer literature and double-blind, controlled trials. Where appropriate, information was obtained from meta-analyses, systematic reviews, or other high-quality reviews, such as those authored by recognized experts. Case reports of adverse effects and interactions, although anecdotal in nature, were used to identify and describe uncommon but potentially serious adverse events that may not have been noted in controlled studies because of small sample size or short duration.

Each of the chapters in this volume includes an Introduction, which contains a review of the product's history and a description of the plant. This is followed by sections on Commonly Promoted Uses, Sources and Chemical Composition, and descriptions of Products Available, which is kept general because of the myriad and ever-changing products on the market. Product quality is also discussed in this section. The Pharmacological/Toxicological Effects section focuses on in vitro data and animal studies chosen to provide an explanation for the herb's mechanism of action, clinical effects in humans, and rationale for clinical studies. It should be noted that because of the nature of herbal supplement claims (see Regulatory Status section), some promoted product uses might not have been studied in humans; conversely, known pharmacological and therapeutic effects might not be promoted commercially as a result of limitations in the ability of manufacturers to make "health claims" related to known pharmacological effects of various herbs. As a result, there is generally a mismatch among the nature of the information presented in the Commonly Promoted Uses and Pharmacological/Toxicological Effects sections. However, emphasis is placed on inclusion of basic science data and clinical studies that relate to the promoted uses.

The Pharmacokinetics section of each chapter covers absorption, tissue distribution, elimination, and body fluid concentrations. Such pharmacokinetic information is usually not included in other sources and may be useful in forensic investigations or in the clinical setting regarding use of the product in patients with renal or hepatic insufficiency. A section on Adverse Effects and Toxicity follows and includes detailed information on case reports of adverse reactions to the herb. The Interactions section includes discussions of interactions between the supplement and drugs or foods. The Reproduction section follows and is generally limited because of lack of information. Each chapter ends with a discussion of Regulatory Status of the product. The amount of information included in each of these sections varies according to availability.

Adverse reactions to herbals appear uncommon compared with those attributed to prescription drugs. This may be a function of health care and forensic professionals' unfamiliarity with the products' pharmacology and toxicology or assumption that the products are "natural" and therefore safe. Thus, an adverse reaction may go unrecognized or be attributed to a prescription medication.

It is hoped that the information in Herbal Products: Toxicology and Clinical Pharmacology, Second Edition will be used to solve clinical or forensic problems involving dietary supplements, promote dialogue between health care professionals and patients, and stimulate intellectual curiosity about these products, fostering further research into their therapeutic and adverse effects.

Timothy S. Tracy, PhD Richard L. Kingston, PharmD

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