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: 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 […]

Policosanol: Clinical Use. Dosage

Most clinical studies have been conducted in Cuba with policosanol derived from sugar cane. HYPERLIPIDAEMIA Numerous randomised, double-blind clinical trials conducted prior to 2005 demonstrated significant cholesterol-lowering effects of oral policosanol; however, one recent study has produced negative results. Several previous studies conducted with postmenopausal women have confirmed efficacy in this population. Overall, these results show that a daily dose of 5 mg policosanol may: • reduce LDL-cholesterol by 11 -18% • reduce total cholesterol by 8-1 5% • increase HDL by 8-1 5% Whereas a higher dose of 20 mg policosanol daily can: • reduce LDL-cholesterol by 31% • reduce total cholesterol by 23% • increase HDL by 27%. Recent controversy It is important to note that previous research had been conducted almost entirely by the same research group in Cuba and involved Hispanic patients. In 2006, Berthold et al conducted a 12-week randomised study of 143 Caucasian subjects with hypercholesterolaemia or combined hyperlipidaemia. In contrast to previous studies, policosanol failed to significantly reduce LDL-cholesterol, total cholesterol, HDL-cholesterol, triglycerides and other lipid Read more […]

Oats: Adverse Reactions. Interactions. Pregnancy Use.

Adverse Reactions Excessive intake of fibre from oats or oat bran may cause flatulence and anal irritation. Significant Interactions Controlled studies are largely unavailable; therefore, interactions are based on evidence of activity and are largely theoretical and speculative. ANTIHYPERTENSIVES Additive effects are theoretically possible; beneficial interaction is possible — observe. Patients taking oats, oat milk or oat bran should be monitored, as medication requirements may alter. LIPID-LOWERING MEDICATIONS Additive effects are theoretically possible — beneficial interaction is possible. Patients taking oats, oat milk or oat bran should be monitored, as medication requirements may alter. Conversely, two case reports exist of a reduced effect of lovastatin in patients taking 50-100 g oatbran daily. As this is likely to be due to the fibre inhibiting absorption of the drug doses should be separated by 2-3 hours. Clinical note — Do oats interfere with nutrient absorption? Although the high phytate content of oats would indicate a potential for reduced absorption of trace elements such as zinc, calcium and iron, one clinical trial investigating the effects of oat bran on zinc absorption found no evidence Read more […]