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: 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: Natural coumarins

Natural coumarins are widespread in herbal medicines and vegetables. There is a misconception that if a plant contains natural coumarins it will have anticoagulant properties, but very specific structural requirements are necessary for this – namely there must be a non-polar carbon substituent at the 3-position of 4-hydroxycoumarin. Moreover, at present, there are no established interactions between warfarin and herbal medicines that have been attributed to the natural coumarin content of the herb. Even in the classic case of haemorrhagic death of livestock that led to the discovery of dicoumarol, it was the action of the mould on the natural coumarin in the sweet clover (melilot) that led to the production of the anticoagulant, so consumption of a spoiled product would seem to be necessary for this specific interaction to occur. This suggests that the occurrence of natural coumarins in dietary supplements or herbal medicines should not trigger immediate concern as regards interactions with anticoagulants. The information in this family monograph relates to the individual natural coumarins, and the reader is referred back to the herb (and vice versa) where appropriate. Note that, to avoid confusion with the synthetic 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: 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 […]

Peppermint: Contraindications and Precautions. Pregnancy Use

Significant Interactions Controlled studies are not available; therefore, interactions are based on evidence of activity and are largely theoretical and speculative. FELODIPINE Peppermint oil has been shown to increase the oral bioavailability of felodipine in animal studies — use this combination with caution. SIMVASTATIN Peppermint oil has been shown to increase the oral bioavailability of simvastatin in animal studies. Observe the patient and monitor drug requirements — possible beneficial interaction. CYCLOSPORIN Peppermint oil has been shown to increase the oral bioavailability of cyclosporin in animal studies — avoid concurrent use, unless under medical supervision. DRUGS METABOLISED BY CYP3A4 LIVER ENZYME Peppermint may increase the oral bioavailability of certain drugs by inhibition of CYP3A4-mediated drug metabolism, which has been demonstrated in vitro but not in test animals. Although these studies seem to suggest that peppermint may modulate drug metabolising enzymes, the clinical significance of this is unknown and requires further investigation. Caution is advised. Contraindications and Precautions Hypersensitivity to peppermint oil. Non-enteric-coated peppermint may be best avoided Read more […]