Asteraceae: Drug Interactions, Contraindications, And Precautions

Patient survey data from Canada, the U.S., and Australia show that one in five patients use prescription drugs concurrently with CAM. The inherent polypharmaceutical nature of complementary and alternative medicine increases the risk of adverse events if these complementary and alternative medicine either have pharmacological activity or interfere with drug metabolism. Since confirmed interactions are sporadic and based largely on case reports, advice to avoid certain drug-CAM combinations is based on known pharmacological and in vitro properties. Known Hypersensitivity to Asteraceae Cross-reactive sesquiterpene lactones are present in many, if not all, Asteraceae. Patients with known CAD from one plant may develop similar type IV reactions following contact with others. Affected patients are often advised to avoid contact with all Asteraceae, yet this advice is based on limited knowledge of cross-reactivity between relatively few members of this large family. Some authorities recommend avoiding Asteraceae-derived complementary and alternative medicine if, for example, the patient is known to have IgE-mediated inhalant allergy to ragweed. While a reasonable approach, this ignores a number of important facts: (1) Read more […]

Herbal Medicines

Herbal medicines are medicines made from plants. A survey of some 259 of the most widely used plants in western herbal medicine in Australia found that the vast majority are flowering plants (angiosperms). Approximately one-third of the species belong to just five botanical families: the daisy family (Asteraceae), mint family (Lamiaceae), rose family (Rosaceae), carrot family (Apiaceae) and legume family (Fabaceae). The study also surveyed the biogeographical origin of medicinal species and the morphological plant parts used for medicinal purposes. These results are shown in Table Biogeographical origin of 259 species used in western herbal medicine and Table Morphological plant part used for medicine respectively. Table Biogeographical origin of 259 species used in western herbal medicine (after Wohlmuth 2002) Europe/Europe and parts of Asia 37.4% Asia 19.3% Africa 3.0% North America 21.6% South America 3.5% Pacific (incl. Australia) 1.2% Native to several continents 14.0% Table Morphological plant part used for medicine (after Wohlmuth 2002) Plant part used Aerial parts 37.8% Underground parts 27.8% Fruit/seed 13.9% Bark 8.5% Flower 4.6% Herbal Read more […]

Herb-Drug Interactions: St John’s wort

Hypericum perforatum L. (Clusiaceae) Synonym(s) and related species Hypericum, Millepertuis. Hypericum noeanum Boiss., Hypericum veronense Schrank. Pharmacopoeias St John’s Wort (British Ph 2009, European Ph 2008, US Ph 32); St John’s Wort Dry Extract, Quantified (British Ph 2009, European Ph, 6th ed., 2008 and Supplements 6.1, 6.2, 6.3 and 6.4). Constituents The main groups of active constituents of St John’s wort are thought to be the anthraquinones, including hypericin, isohypericin, pseudohypericin, protohypericin, protopseudohypericin and cyclopseudohypericin, and the prenylated phloroglucinols, including hyperforin and adhyperforin. Flavonoids, which include kaempferol, quercetin, luteolin, hyperoside, isoquercitrin, quercitrin and rutin; biflavonoids, which include biapigenin and amentoflavone, and catechins are also present. Other polyphenolic constituents include caffeic and chlorogenic acids, and a volatile oil containing methyl-2-octane. Most St John’s wort products are standardised at least for their hypericin content (British Pharmacopoeia 2009), even though hyperforin is known to be a more relevant therapeutic constituent, and some preparations are now standardised for both (The United Read more […]

Herb-Drug Interactions: Red clover

Trifolium pratense L. (Fabaceae) Synonym(s) and related species Cow clover, Meadow clover, Purple clover, Trefoil. Trifolium borysthenicum Gruner, Trifolium bracteatum Schousb., Trifolium lenkoranicum (Grossh.) Rosk., Trifolium ukrainicum Opp. Not to be confused with melilot, which is known as sweet clover. Pharmacopoeias Powdered Red Clover (US Ph 32); Powdered Red Clover extract (US Ph 32); Red Clover (US Ph 32); Red Clover Tablets (The United States Ph 32). Constituents Red clover flowers contain isoflavones, to which they may be standardised. The major isoflavones are biochanin A and formononetin, with small amounts of genistein and daidzein and others, and their glycoside conjugates. Other constituents include clovamides, coumestrol, and the natural coumarins medicagol and coumarin. Use and indications Red clover was traditionally used for skin conditions, such as eczema and psoriasis. However, the isoflavone fraction is now more commonly used as a form of HRT in women to reduce the symptoms of the menopause, although randomised controlled studies show only a slight benefit at best. It is also used for mastalgia, premenstrual syndrome and cancer prevention. Pharmacokinetics In an in vitro study, Read more […]

Herb-Drug Interactions: Kudzu

Pueraria montana (Lour.) Merr. (Fabaceae) Synonym(s) and related species Ge Gen. Pueraria hirsuta (Thunb.) C. Schneider, Pueraria lobata (Willd.) Ohwi, Pueraria lobata (Willd.) Ohwi var. thomsonii (Benth.) Maesen, Pueraria thunbergiana (Sieb. & Zucc.) Benth., Dolichos lobatus Willd. Other species used include Pueraria mirifica Airy Shaw & Suvatabandhu (Thai kudzu, Kwao Kreu Kao) and Pueraria phaseoloides (Roxb.) Benth. (Puero, Tropical kudzu). Constituents The major isoflavone constituent of the root of Pueraria lobata is puerarin, which is the 8-C-glucoside of daidzein, but there are many others, such as puerarin hydroxy- and methoxy- derivatives and their glycosides, daidzein and its O-glycoside daidzin, biochanin A, genistein and formononetin derivatives. Pterocarpans are also present, including medicarpin glycinol and tuberosin. The flowers contain the phytoestrogens kakkalide and tectoridin. Pueraria mirifica root contains similar constituents to Pueraria lobata, the major difference being lower amounts of daidzein. Much of the research carried out on kudzu has been on the effects of isolated puerarin. Use and indications Kudzu contains isoflavones and is used as a phytoestrogen for Read more […]

Herb-Drug Interactions: Isoflavones

Isoflavonoids This is a large group of related compounds with similar structures and biological properties in common, which are widely available as additives in dietary supplements as well as the herbs or foods that they were originally derived from. Isoflavones are the subject of intensive investigations and new information is constantly being published. You may have come to this monograph via a herb that contains isoflavones. The information in this monograph relates to the individual isoflavones, and the reader is referred back to the herb (and vice versa) where appropriate. It is very difficult to confidently predict whether a herb that contains one of the isoflavones mentioned will interact in the same way. The levels of the isoflavone in the particular herb can vary a great deal between specimens, related species, extracts and brands, and it is important to take this into account when viewing the interactions described below. Types, sources and related compounds Isoflavones are plant-derived polyphenolic compounds that are a distinct group of flavonoids. They can exert oestrogen-like effects, and therefore belong to the family of ‘phytoestrogens’. Most occur as simple isoflavones, but there are other derivatives Read more […]

Herb-Drug Interactions: Grapefruit

Citrus paradisi Macfad. (Rutaceae) Synonym(s) and related species Citrus paradisi Macfad. Grapefruit is a hybrid of the Pummelo or Pomelo (Citrus maxima (Burm.) Merr) with the sweet orange (Citrus sinensis (L.) Osbeck). Constituents Grapefruit contains furanocoumarins including bergamottin, 6′,7′-dihydroxybergamottin, bergapten, bergaptol, geranyl-coumarin and paradisin A, flavonoid glycosides such as naringin and flavonoid aglycones galangin, kaempferol, morin, naringenin, quercetin and others. The peel contains a volatile oil, mostly composed of limonene. Note that some grapefruit seed extracts have been found to contain preservatives such as benzethonium chloride, triclosan and methyl-p-hydroxybenzoate, which might be present because of the methods of production. Use and indications Grapefruit is used as a source of flavonoids (citrus bioflavonoids), which are widely used for their supposed antioxidant effects, and are covered under flavonoids. Grapefruit seed extracts are used for their antimicrobial properties, but there is some controversy that this might be due to preservative content rather than natural constituents. Grapefruit and grapefruit juice are commonly ingested as part of the diet, Read more […]

Herb-Drug Interactions: Ginkgo

Ginkgo biloba L. (Ginkgoaceae) Synonym(s) and related species Fossil tree, Kew tree, Maidenhair tree. Salisburia adiantifolia Sm., Salisburia biloba Hoffmanns. Pharmacopoeias Ginkgo (US Ph 32); Ginkgo capsules (US Ph 32); Ginkgo dry extract, refined and quantified (British Ph 2009, European Ph 2008); Ginkgo leaf (British Ph 2009, European Ph, 6th ed., 2008 and Supplements 6.1, 6.2, 6.3 and 6.4); Ginkgo tablets (US Ph 32); Powdered ginkgo extract (The United States Ph 32). Constituents Ginkgo leaves contain numerous flavonoids including the biflavone glycosides such as ginkgetin, isoginkgetin, bilobetin, sciadopitysin, and also some quercetin and kaempferol derivatives. Terpene lactones are the other major component, and these include ginkgolides A, B and C, and bilobalide, Ginkgo extracts may be standardised to contain between 22 and 27% flavonoids (flavone glycosides) and between 5 and 12% terpene lactones, both on the dried basis. The leaves contain only minor amounts of ginkgolic acids, and some pharmacopoeias specify a limit for these. The seeds contain ginkgotoxin (4-O-methylpyridoxine) and ginkgolic acids. Use and indications The leaves of ginkgo are the part usually used. Ginkgo is often used Read more […]

Herb-Drug Interactions: Flavonoids

Bioflavonoids The flavonoids are a large complex group of related compounds, which are widely available in the form of dietary supplements, as well as in the herbs or foods that they are originally derived from. They are the subject of intensive investigations and new information is constantly being published. You may have come to this monograph via a herb that contains flavonoids. Note that the information in this general monograph relates to the individual flavonoids, and the reader is referred back to the herb (and vice versa) where appropriate. It is very difficult to confidently predict whether a herb that contains one of the flavonoids mentioned will interact in the same way. The levels of the flavonoid in the particular herb can vary a great deal between specimens, related species, extracts and brands, and it is important to take this into account when viewing the interactions described below. Types, sources and related compounds Flavonoids are a very large family of polyphenolic compounds synthesised by plants that are common and widely distributed. With the exception of the flavanols (e.g. catechins) and their polymers, the proanthocyanidins, they usually occur naturally bound to one or more sugar molecules Read more […]