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 […]

GASTRIC SECRETION INHIBITORS

GASTRIC SECRETION INHIBITORS act at some stage in the control process to inhibit the enzymic or gastric acid secretions of the stomach, with the latter being a major therapeutic target. The neuronal, hormonal and paracrine control of gastric acid secretion from the parietal cells of the gastric mucosa is complex. The pathways involved include acetylcholine via the parasympathetic innervation of the stomach, the hormone gastrin. the paracrine agent histamine and possibly the paracrine hormone gastrin-releasing peptide. Anticholinergic agents have not proved very valuable in the long-run, having a limited ability to reduce acid secretion at doses that can be tolerated in view of widespread side-effects. Some more recently developed agents show gastric-selectivity (they are Mrcholinoceptor-preferring ligands, which may be the reason for their selectivity), e.g. pirenzepine and telenzepine: see muscarinic cholinoceptor antagonists. Gastrin receptor antagonists and gastrin-releasing peptide antagonists have now been developed for experimental use, but it is not yet clear if either will be useful clinically. See BOMBESIN RECEPTOR ANTAGONISTS; CHOLECYSTOKININ RECEPTOR ANTAGONISTS. Histamine H2-receptor antagonists Read more […]

Heartburn

Heartburn (Gastroesophageal Reflux) In Pregnancy Heartburn is caused by a reflux of gastric acids into the lower esophagus, usually occurring after meals or when lying down. The gastric acids irritate the esophagus, causing a burning sensation behind the sternum that may extend into the neck and face, and may be accompanied by regurgitation, nausea, and hypersalivation. Inflammation and ulceration of the esophagus may result. Up to two-thirds of women experience heartburn during pregnancy. Only rarely it is an exacerbation of preexisting disease. Symptoms may begin as early as the first trimester and cease soon after birth. Most women first experience reflux symptoms after 5 months of gestation; however, many women report the onset of symptoms only when they become very bothersome, long after the symptoms actually began. The prevalence and severity of heartburn progressively increases during pregnancy. The exact causes(s) of reflux during pregnancy include relaxed lower esophageal tone, secondary to hormonal changes during pregnancy, particularly the influence of progesterone, and mechanical pressure of the growing uterus on the stomach which contributes to reflux of gastric acids into the esophagus. However, some Read more […]

ATPase INHIBITORS

ATPase INHIBITORS are inhibitors of ATP-driven transporter systems in the body, including Na+/K+-ATPase, H+/K+-ATPase and Ca2+-ATPase. Some are important sites of drug action and will be described from a functional, rather than a biochemical or structural viewpoint. The Na+/K+-ATPase of the cell membrane, which constitutes the Na+/K+ pump, is the main site at which cardiac glycosides act. They bind to the K+-binding site, thus inhibiting the enzyme, and this inhibition, through a series of interrelated actions, eventually affects cardiac rhythm and the force of contraction is increased. These are the principal beneficial actions. Examples include digoxin, digitoxin and ouabain. See cardiac glycosides. The Na+/K+/2Cl- transport system in the thick ascending loop of Henle in the kidney is a major site of action of diuretics. Here there is active reabsorption of sodium chloride, not accompanied by water, which reduces the osmolarity of the tubular fluid and makes the interstitial fluid of the medulla hypertonic. Sodium and chloride move into the cell by a cotransport system involving Na+,K+,2Cl-, a process driven by the electrochemical gradient for sodium produced by the Na+/K+-ATPase in the basolateral membrane. Read more […]

ANTIULCEROGENIC AGENTS

ANTIULCEROGENIC AGENTS (or ulcer-healing drugs) are used to promote healing of ulceration of gastric and duodenal peptic ulcers. A number of classes of drugs may be used. See also gastric secretion inhibitors. First, the HISTAMINE H2-ANTAGONISTS are very effective and have considerable usage, e.g. cimetidine. famotidine, nizatidine and ranitidine. These agents decrease gastric acid secretion and promote healing and may be used to treat dyspepsia and oesophagitis of a number of etiologies. Acid production is also very effectively reduced by the newer agents, the proton pump inhibitors, e.g. omeprazole (see GASTRIC PROTON PUMP INHIBITORS). Anticholinergic drugs are only really suitable in the case of agents that show some gastric-selectivity, e.g. pirenzepine and telenzepine (see muscarinic cholinoceptor ANTAGONISTS). They work by reducing the secretion of peptic acid by the stomach mucosa. Some prostaglandin analogues are effective in protecting the mucosa, and are incorporated into some preparations of NSAIDs to offer concurrent protection (though they may cause unacceptable stimulation of the ileum), e.g. misoprostol. (see prostanoid receptor agonists) . Bismuth-containing antacid preparations have been 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: Liquorice

Qycyrrhiza glabra L. (Fabaceae) Synonym(s) and related species Licorice. Spanish and Italian liquorice is Glycyrrhiza glabra var typica Reg. et Herd. Persian or Turkish liquorice is Glycyrrhiza glabra L var violacea Boiss. Russian liquorice is Glycyrrhiza glabra L var glanduli-fera. Chinese liquorice is the closely related Glycyrrhiza uralensis Fisch., also known as Gancao. Pharmacopoeias Licorice (US Ph 32); Liquorice (British Ph 2009); Liquorice Dry Extract for Flavouring Purposes (British Ph 2009); Liquorice Liquid Extract (British Ph 2009); Liquorice Root (European Ph 2008); Liquorice Root for use in THM (British Ph 2009); Powdered Licorice (US Ph 32); Powdered Licorice Extract (US Ph 32); Processed Liquorice Root for use in THMP (British Ph 2009); Standardised Liquorice Ethanolic Liquid Extract (British Ph 2009, European Ph, 6th ed., 2008 and Supplements 6.1, 6.2, 6.3 and 6.4). Constituents Liquorice has a great number of active compounds of different classes that act in different ways. The most important constituents are usually considered to be the oleanane-type triterpenes, mainly glycyrrhizin (glycyrrhizic or glycyrrhizinic acid), to which it is usually standardised, and its aglycone glycyrrhetinic Read more […]

Herb-Drug Interactions: Grapeseed

Vitis vinifera L. (Vitaceae) Synonym(s) and related species Vitis vinifera is the Grape vine, of which there are many cultivars. Constituents Grapeseed extract contains flavonoids, which include gallic acid, catechin, (—)-epicatechin, and their galloylated derivatives, and proanthocyanidins. Resveratrol, a polyphenolic stilbene derivative, and tocopherols and tocotrienols are also present. Use and indications Grapeseed extract is promoted as an antioxidant supplement for preventing degenerative disorders in particular, in the same way as other flavonoid-containing products. The in vitro antioxidant properties are well documented and there is some clinical evidence to suggest that it can promote general cardiovascular health. Pharmacokinetics An in vitro study found that grapeseed extract potently inhibits CYP3A4, but only when the catechin content is high. In contrast, another in vitro study found that grapeseed extract is a weak inducer of the cytochrome P450 isoenzyme CYP3A4. The author suggests that grapeseed therefore has the potential to cause interactions. However, the effect of grapeseed extract was less than that of omeprazole, which does not commonly interact by this mechanism, suggesting that 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 […]

Fenugreek: Background. Actions

Historical Note Fenugreek’s seeds and leaves are used not only as food but also as an ingredient in traditional medicine. It is indigenous to Western Asia and Southern Europe, but is now mainly cultivated in India, Pakistan, France, Argentina and North African countries. In ancient times it was used as an aphrodisiac by the Egyptians and, together with honey, for the treatment of rickets, diabetes, dyspepsia, rheumatism, anaemia and constipation. It has also been described in early Greek and Latin pharmacopoeias for hyperglycaemia and was used by Yemenite Jews for type 2 diabetes. In India and China it is still widely used as a therapeutic agent. In the United States, it has been used since the 19th century for postmenopausal vaginal dryness and dysmenorrhea. Common Name Fenugreek Other Names Trigonella seeds, bird’s foot, Greek hay, hu lu ba, methi, trigonella Botanical Name / Family Trigonella foenum graecum (family Leguminosae) Plant Parts Used Dried mature seed, although leaves are used less commonly. Chemical Components The main chemical constituents are fibre, tannicacid, fixed and volatile oils and a bitter extractive, steroidal saponins, flavonoids, polysaccharides, alkaloids, trigonelline, trigocoumarin, Read more […]