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PDR for Herbal Medicines, 2nd ed

by Dennis V.C. Awang, Ph.D., F.C.I.C.

PDR for Herbal Medicines, 2nd edition, edited by Joerg Gruenwald, Ph.D., Thomas Brendler, Christof Jaenicke, M.D. Medical Economics Co.: Montvale, NJ; 2000. 858 pp. hardcover $59.95 ISBN 1-56363-361-2

When the late Prof. Varro E. (Tip) Tyler, reviewed the first edition of this work in HerbalGram 46, he made a number of criticisms of it, as well as suggestions for its improvement. The German editors, given the opportunity to comment on Prof. Tyler’s review, promised to implement his suggestions in a timely fashion "wherever possible and appropriate." Salient among Tyler’s criticisms of the volume was the uncritical character of its monographs, omission of significant botanicals, and inclusion of a number of toxic and clinically "insignificant" herbs. This from a book touted as "The Information Standard for Complementary Medicine" and aimed at physicians. He further advised that "The clinical utility of the PDR for Herbal Medicines could have been greatly improved by judicious editing."

The second edition is similarly in need of expert scientific editing – as well as proof reading. The carelessness evident in both areas is prevalent enough to enervate knowledgeable herbal scientists. A number of egregious examples will be provided later in this review, but the shoddiness of editing is nowhere more evident than in the kava kava entry, where, under the contraindications heading, two virtually identical sentences caution against its use in patients with endogenous depression because of an increased risk of suicide.

The number of entries in the second edition increased from 600 or so in the first to more than 700. While in their comments about the review of the first edition the editors expected it "to steadily improve and expand," such a large expansion does not seem to be warranted given the rate of development of new medicinal plant treatments. They have not eliminated any of the monographs dealing with very toxic and clinically insignificant plants, and only one of Tyler’s noted omissions (cat’s claw) has been included (Unicaria [sic] tomentosa) in the Alphabetical Index which precedes the main body of the text. Soybean is still represented as the wild species Glycine soja instead of the commercial cultigen G. max. It would be interesting to review the rest of the hundred or so new entries, roughly equal in number to the herbs of major significance in North America.

Nevertheless, the second edition is considerably improved over the first, including recent literature references and information on herb-drug interactions such as those involving St. John’s wort (SJW). However, even with these additions there is a lack of critical attention to published research results, as in perpetuating the erroneous notion that SJW has potential for reproductive toxicity, and promoting the long-discredited theory that hypericin is the SJW principle responsible for its anti-depressant activity: "In general a range of 200 to 1000 micrograms/day of hypericin is recommended for treatment of depression (Anon, 1996)."

While much prominence is given to the judgments of the German Commission E, these bulleted lists of abbreviated indications neglect the Commission’s findings that some 600 plants did not have sufficient research to support safety or efficacy recommendations. Occasional inaccuracies appear, such as in the case of rosemary and yarrow: the PDR erroneously states that the Commission E approved rosemary’s use for: blood pressure problems, loss of appetite, rheumatism. However, the Commission cites rosemary leaf use only for dyspeptic complaints, at least insofar as the monograph published in ABC’s The Complete Commission E Monographs, for which Dr. Gruenwald was an associate editor. Interestingly, Tyler wrote in Tyler’s Honest Herbal (Haworth Herbal Press, 1999) that it is used to treat low blood pressure, while the British Herbal Pharmacopoeia lists as indication: "headaches migrainous or hypertensive." Also inexplicably, the PDR adds to the Commission E approvals for yarrow: "Liver and gallbladder complaints," which are not listed in the ABC publication.

Regarding format, the second edition, sensibly, has altered the vast majority of monograph headings to give priority to common names, inferiorly listing Latin binomials in their accustomed italics. However, the binomials are not italicized in the main text, as they ought to be. It also seems unnecessary to retain the original heading entries in the main body of text since the Latin binomials are available in the Alphabetical Index for those unfamiliar with the respective common names. A final note regarding Latin binomials: No naming authorities are given, nor are any synonyms. While this neglect is often inconsequential, there are instances where confusion could occur with inexpert readers. For example, in much of the European literature saw palmetto is referred to as Sabal serrulata rather than the designation Serenoa repens common in North America. Also, while German chamomile is currently widely represented as Matricaria recutita, the earlier binomials M. chamomilla and Chamomilla recutita are still occasionally encountered today.

There is a disconcerting situation respecting the literature listings and textual references, when they occur. There are some monographs with numerous literature listings that have no correlation with the monograph text (e.g., 34 unreferenced literature listings under wormwood). The situation is further confounded by the fact that a number of literature citations do not include the title of the publication, and some are incorrect: in both the ginger and wormwood monographs, a paper by Marles et al. is cited as being "In: JNP 55: 1044-1056, 1992". However, the JNP paper included me as an author and has a different author list than that cited. In any event, ginger was found not to inhibit serotonin release from blood platelets, the scientific focus of the subject bioassay – and there is no indication in the wormwood monograph of any relation to such function. In the case of feverfew, there are two references to "Groenewegen, 1986" in the monograph text but the literature listing notes two publications attributed to Groenewegen in 1986, both without titles.

In addition to annoying misspellings – notably "partholide" repeatedly for parthenolide, which is particularly confusing to those unfamiliar with feverfew chemistry, since secotanapartholide A is regarded as one of the plant’s significant actives – more serious is the attribution of dominant activity to parthenolide, especially regarding feverfew’s anti-migraine effect. It is stated that "the usual standardization level is 0.2 percent parthenolide content," but since 1996 it has been apparent that parthenolide is not a significant contributor to feverfew’s migraine prophylactic effect. In fact, the 0.2 percent parthenolide minimum was meant as an identity criterion, established by the Canadian regulatory agency in an attempt to ensure similarity to the clinically tested feverfew chemotype: at least two other feverfew sesquiterpene lactone chemotypes contain no parthenolide. Finally, regarding feverfew drug interactions, the statement that "there is a strong possibility that Feverfew may interact with thrombolytics, anticoagulants and platelet aggregation" is simply not supported by recorded experience: no case of a bleeding problem has ever been associated with feverfew use. Such speculation is based entirely on in vitro laboratory observation of an anti-platelet aggregation effect.

The heading Ginseng, Panax ginseng, (Asian Ginseng)is followed by a list of Trade Names, which include "Siberian Ginseng…American Ginseng Root…Standardized Siberian Ginseng Root….Siberian Ginseng Power Herb…Eleuthero Ginseng Root, Siberian Ginseng Root." A later listing is Siberian Ginseng, Eleutherococcus senticosus. The American Herbal Products Association wisely recognizes eleuthero as the preferred common name for E. senticosus, acknowledging, as the U.S. Congress has recently, that only Panax species may legitimately be claimed to be ginseng.

Under Actions and Pharmacology are listed protopanaxadiol ginsenosides, "protopanaxytriol" [sic] ginsenosides, and oleanolic acid ginsenosides. No mention is made of the significant panaxatriol ginsenoside Rg2, and mentioned as oleanolic acid derivatives are ginsenoside Ro, chikusetsusaponin—V and Rb1, Rb2, Rc, Rd, Re and Rg1: Rb1, Rb2, Rc and Rd are protopanaxadiol glycosides, while Re and Rg1 are protopanaxatriol derivatives. Ginsenoside Ro is the only oleanolic acid derivative present in Asian and American ginsengs; it is identical with chikusetsusaponin-V, first identified in Japanese ginseng (P. japonicus).

In summary, while this very substantial volume contains much useful factual information on a vast array of medicinal plants, its striking deficiencies and extensive errors of both commission and omission seriously limit its usefulness while promoting an inaccurate appreciation of many of the more important and commercially prominent herbal preparations.

– Dennis V.C. Awang, Ph.D.

MediPlant Consulting Inc.

White Rock, BC, Canada