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 […]

Herb-Drug Interactions: Chinese angelica

Angelica sinensis (Oliv.) Diels (Apiaceae) Synonym(s) and related species Dang Gui (Chinese), Danggui, Dong quai. Angelica polymorpha van sinensis. Other species used in oriental medicine include Angelica dahurica. Not to be confused with Angelica, which is Angelica archangelica L. Pharmacopoeias Angelica Sinensis Root for use in THM (British Ph 2009); Processed Angelica Sinensis Root for use in THMP (British Pharmacopoeia 2009). Constituents The major constituents include natural coumarins (angelicin, archangelicin, bergapten, osthole, psoralen and xanthotoxin) and volatile oils. Other constituents include caffeic and chlorogenic acids, and ferulic acid. Angelica sinensis also contains a series of phthalides (n-butylidenephthalide, ligustilide, n-butylphthalide). Use and indications One of the most common uses of Chinese angelica root is for the treatment of menopausal symptoms and menstrual disorders. It has also been used for rheumatism, ulcers, anaemia, constipation, psoriasis, the management of hypertension and to relieve allergic conditions. Pharmacokinetics Evidence is limited to experimental studies, which suggest that the effects of Angelica dahurica and Angelica sinensis may not be equivalent. Read more […]

Herb-Drug Interactions: Cranberry

Vaccinium macrocarpon Aiton (Ericaceae) Synonym(s) and related species Large cranberry (Vaccinium macrocarpon) is the cultivated species. European cranberry or Mossberry (Vaccinium oxycoccus) has also been used. Pharmacopoeias Cranberry Liquid Preparation (The United States Ph 32). Constituents The berries contain anthocyanins and proanthocyanidins (mainly oligomers of epicatechin), and organic acids including malic, citric, quinic and benzoic acids. Note that, although salicylic acid does not appear as a constituent of the juice in many cranberry monographs, some studies have shown low levels of salicylates in commercial cranberry juice (e.g. 7mg/L), which resulted in detectable plasma and urine levels of salicylic acid in women who drank 250 mL of cranberry juice three times daily. Use and indications The main use of cranberries and cranberry juice is for the prevention and treatment of urinary tract infections, although they have also been used for blood and digestive disorders. Cranberries are commonly used in food and beverages. Pharmacokinetics There is high absorption and excretion of cranberry anthocyanins in human urine, as shown by a study where 11 healthy subjects drank 200 mL of cranberry Read more […]


CALCIUM-CHANNEL BLOCKERS are agents that literally block or close any of the many types of calcium channels. However, in common usage the term is mainly used to describe a class of drugs finding increasing application in therapeutics (also called calcium antagonists or calcium-entry blockers) typified by the dihydropyridines (DHPs). In a more general usage of the term, there are many different classes of calcium-channel blockers, and many types of calcium channels. See CALCIUM-CHANNEL ACTIVATORS. First, in the cell membrane, the voltage-gated calcium channels are of at least six types — termed L, N, T, P, Q, R — that may be differentiated by electrophysiological, molecular cloning and pharmacological criteria. The L- and N-channels are high-voltage activated, voltage-dependent and undoubtedly of great importance in normal physiology; L mainly in smooth, cardiac and skeletal muscle (and some neurons), but N only in neurons. T-channels are important in repetitive activity in cardiac SA node of the heart, neurons and some endocrine cells. The remainder have been found more recently in neurons. These channels are products of different genes, but they all share great structural similarity — both with respect to 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: Schisandra

Schisandra chinensis K.Koch (Schisandraceae) Synonym(s) and related species Gomishi (Japanese), Magnolia vine, Wu-Wei-Zi (Chinese). Kadsura chinensis Turcz. Schisandra sphenanthera Rehder & EH Wilson is often used with, or substituted for, Schisandra chinensis. Other species of Schisandra are also used medicinally in China. Constituents The major active components of the fruits of Schisandra chinensis are dibenzocyclooctene lignans. The identity and nomenclature are confusing, because, when originally isolated by different researchers, the same compounds were given different names. The main groups of compounds are the schisandrins (schizandrins) and the gomisins (some of which were originally called wuweizu esters) and their derivatives. Schisandrin is also referred to in the literature as schisandrol A, gomisin A as schisandrol B, deoxyschisandrin as schisandrin A or wuweizu A, and schisantherin B as gomisin B or wuweizu B, for example. An essential oil contains borneol, 1,8-cineole, citral, sesquicarene and other monoterpenes. Extracts of Schisandra sphenanthera are reported to have a fairly similar chemical composition. Use and indications Schisandra is a very important herb in Chinese medicine. Read more […]

Herb-Drug Interactions: Policosanol

Types, sources and related compounds Octacosanol. Constituents Policosanol consists of a mixture of alcohols with octacosanol being the major component. Triacontanol and hexacosanol are also present but in lesser amounts. Use and indications Policosanol is isolated from sugar cane wax and, because of its lipid-lowering and antiplatelet properties, is mainly used for cardiovascular disorders. It is also being investigated for possible use in the treatment of Parkinson’s disease, and for enhancing athletic performance. Pharmacokinetics Policosanol did not alter the metabolism of phenazone (antipyrine) in dogs. Phenazone is used as a probe drug to assess the effects of other drugs on hepatic enzyme induction and inhibition. This finding therefore suggests that policosanol is unlikely to induce or inhibit the metabolism of other drugs that are substrates of hepatic enzymes. Interactions overview Policosanol has antiplatelet effects, which may be additive with other antiplatelet drugs, and could theoretically increase the risk of bleeding in patients taking anticoagulants. Policosanol may also enhance the blood pressure-lowering effects of some antihypertensives. Policosanol + Anticoagulants The interaction between Read more […]

Herb-Drug Interactions: Peppermint

Mentha piperita L. (Lamiaceae) Synonym(s) and related species Black mint (Mentha piperita Sole), White mint (Mentha piperita Sole). Note that Mentha x piperita L. is a hybrid between Mentha spicata L. and Mentha viridis L. Pharmacopoeias Concentrated Peppermint Emulsion (British Ph 2009); Gastro-resistant Peppermint Oil Capsules (British Ph 2009); Peppermint (US Ph 32); Peppermint Leaf (British Ph 2009, European Ph 2008); Peppermint Leaf Dry Extract (European Ph 2008); Peppermint Oil (British Ph 2009, European Ph 2008, US Ph 32); Peppermint Spirit (British Ph 2009, US Ph 32); Peppermint Water (The United States Ph 32). Constituents Essential oils, including menthol, menthone, menthyl acetate as the main components, and cineole, isomenthone, neomenthol, piperitone, pulegone and limonene. A maximum level of pulegone is permitted, since this is toxic, see pennyroyal. Peppermint also contains flavonoids such as rutin, menthoside, luteolin and phenolic acids, and lactones. Use and indications Peppermint leaf and distilled oil have carminative, antispasmodic, diaphoretic and antiseptic properties, and are mainly used to relieve symptoms of indigestion. Peppermint is commonly used as a flavouring ingredient Read more […]

Herb-Drug Interactions: Pepper

Piper nigrum L. (Piperaceae) Synonym(s) and related species Black and white pepper are derived from the fruits of the same species, Piper nigrum L. Black pepper is the unripe fruit which has been immersed in hot water and dried in the sun, during which the outer pericarp shrinks and darkens into a thin, wrinkled black layer. White pepper consists of the seed only, prepared by soaking the fully ripe berries, removing the pericarp and drying the naked seed. Long pepper, Piper longum L., is a closely related species where the fruits are smaller and occur embedded in flower ‘spikes’, which form the seed heads. Constituents Alkaloids and alkylamides, the most important being piperine, with piperanine, piperettine, piperlongumine, pipernonaline, lignans and minor constituents such as the piperoleins, have been isolated from the fruits of both species of pepper. Black pepper and long pepper also contain a volatile oil which may differ in constitution, but is composed of bisabolene, sabinene and many others; white pepper contains very little. The pungent taste of pepper is principally due to piperine, which acts at the vanilloid receptor. Use and indications Pepper is one of the most popular spices in the world, Read more […]

Herb-Drug Interactions: Milk thistle

Silybum mahanum (L.) Gaertn. (Asteraceae) Synonym(s) and related species Lady’s thistle, Marian thistle, Mediterranean milk thistle, St Mary’s thistle. Carduus marianus, Mariana lactea Hill. Pharmacopoeias Milk Thistle (US Ph 32); Milk Thistle Capsules (US Ph 32); Milk Thistle Fruit (British Ph 2009, European Ph 2008); Milk Thistle Tablets (US Ph 32); Powdered Milk Thistle (US Ph 32); Powdered Milk Thistle Extract (US Ph 32); Refined and Standardised Milk Thistle Dry Extract (British Ph 2009, European Ph, 6th ed., 2008 and Supplements 6.1, 6.2, 6.3 and 6.4). Constituents The mature fruit (seed) of milk thistle contains silymarin, which is a mixture of the flavonolignans silibinin (silybin), silicristin (silychristin), silidianin (silydianin), isosilibinin and others. It may be standardised to contain not less than 1.5% (European Ph, 6th ed., 2008 and Supplements 6.1, 6.2, 6.3 and 6.4), or not less than 2% (The United States Ph 32) of silymarin, expressed as silibinin (dried drug). Standardised extracts, containing high levels of silymarin, are often used. Milk thistle fruit also contains various other flavonoids, such as quercetin, and various sterols. Note that milk thistle leaves do not contain silymarin, Read more […]