Evidence-Based Herbal Medicine
- Sharon E Strauss, MD
The volume of literature on herbal medicines can be overwhelming. The authors of Evidence-Based Herbal Medicine state that clinicians are inundated with data from patients, the media, and the internet and that this material is often confusing because it is based on incomplete or biased knowledge. They maintain that few high quality evidence resources tackle this topic. Rotblatt and Ziment have attempted to meet this need by providing a synopsis of evidence in the field of herbal medicine and offering clinicians “more confident answers to patients’ questions about self-administered herbal remedies”.
Most of the book addresses the use of 65 herbal medications, most of which are well known to clinicians (and patients), including glucosamine, chondroitin, and melatonin. For each herbal remedy, the authors extensively searched the literature for clinical trials using Medline, the Cochrane Library, and bibliographies in herbal textbooks. Unpublished and non-English language studies were included in their searches. Available evidence was analysed and assessed using the authors’ “own judgment as practicing clinicians”. The authors state that they primarily emphasised identifying and appraising randomised clinical trials and systematic reviews of randomised trials. No mention was made of how the authors hope to update the information.
The contents are divided into 4 sections: introduction to herbal medicine, herbal evaluations, special topics, and essays and commentaries. The first section includes an introduction to evidence-based herbal medicine, herbal practices in the US, quality assurance, understanding herbal dosage forms, chemistry of herbal medicine, and herb–drug interactions. The challenges to evidence-based herbal medicine are highlighted, including the poor designs used in many studies, trials that are often done by manufacturers (not unlike many pharmaceutical trials), and the use of non-standardised herbal preparations. Indeed, the authors mention that laboratory analysis of different brands shows that the amounts of important ingredients can vary by up to 40-fold, some samples may contain no labeled product, and some may contain unsafe contaminants. The chapter on herb–drug interactions is useful and highlights a list of herbs, medications that might interact with the herbs, and the type of evidence supporting the putative interaction.
The second section of the book includes evaluations of various herbal medicines. The benefit of each medicine is rated using a scale of 1–3 leaves. One leaf indicates minimal or no evidence of clinical benefit from controlled clinical trials. Two leaves indicate that clinical benefit is suggested by controlled clinical trials, but results conflict or the evidence is not convincing. If convincing evidence of clinical benefit has been shown in several randomised controlled trials, the herbal medication rates 3 leaves. Each medication is also rated for safety: a “+” indicates that the herb is safe and well tolerated with minimal or no adverse effects based on controlled clinical trials and widespread experience, and a “−” safety rating suggests that the medicine causes significant adverse effects or interactions. Each evaluation outlines use of the herbal medicine, its pharmacology, clinical trials of the herbal medicine (including randomised controlled trials and systematic reviews), adverse events (summarising information from clinical trials and from herbal pharmacopoeias), a summary evaluation, and a list of references. A table at the end of this section provides a list of the herbal medicines categorised by levels of evidence (using the authors’ “leaf” rating scale) and indications for use.
The third section of the book includes a discussion of such special topics as Chinese and Mexican herbs. The final section includes discussions about the placebo effect, aromatherapy, and what the authors have learnt. In the last chapter of this section, the authors address problems with the herbal medication literature and provide a list of questions that clinicians might find useful in reviewing literature in this field.
Evidence-Based Herbal Medicine is clear and easy to read. Information on herbal medications can be identified and read quickly. For example, each evaluation begins with a textbox summarising the evidence. Chapters on herb–drug interactions, herb dosages, and herb evaluations are particularly useful for clinicians. I believe that the authors have achieved their goal of creating a useful resource to familiarise clinicians with the evidence in the field of herbal medicine.
Clinical usefulness: ★★★★☆