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 […]

ANTIMIGRAINE DRUGS

ANTIMIGRAINE DRUGS are used to treat migraine attacks, which constitute a specific clinically recognized form of headache. Attacks vary in form, but common characteristics include: throbbing in the head confined to one side only (unilateral headache), nausea and vomiting, and a forewarning of the attack (an aura) consisting of visual disturbances and weakness or numbness of the limbs. Drugs are used to help migraine sufferers (and the related state called ‘cluster headache‘) in two quite distinct ways. One group of drugs is given chronically, and helps to prevent attacks (prophylactic use): such as CALCIUM-CHANNEL BLOCKERS. e.g. nifedipine and verapamil; the β-blockers, e.g. metoprolol, nadolol, propranolol and timolol (see β-ADRENOCEPTOR ANTAGONISTS); and also certain vasoactive drugs, including cyproheptadine and the ergot alkaloid methysergide. All these drugs affect blood vessels. In migraine attacks, cerebral vessels are thought to constrict before an attack, then dilate, causing pain during the attack. A second group of drugs may be used to treat acute attacks, either at the stage of the prewarning aura, or during the attack stage itself; and here speed of administration and subsequent absorption of the Read more […]