Valerian (Valeriana officinalis, Valerianaceae) is a hardy perennial flowering plant, with heads of sweetly scented pink or white flowers which bloom in the summer months. Valerian flower extracts were used as a perfume in the sixteenth century. Native to Europe and parts of Asia, valerian has been introduced into North America. It is consumed as food by the larvae of some Lepidoptera (butterfly and moth) species including Grey Pug. Other names used for this plant include garden valerian (to distinguish it from other Valeriana species), garden heliotrope (although not related to Heliotropium) and all-heal. The garden flower red valerian is also sometimes referred to as "valerian", but is a different species from the same family and not very closely related. Valerian, in pharmacology and phytotherapic medicine, is the name of an herb or dietary supplement prepared from roots of the plant, which, after maceration, trituration and dehydration processes, are packaged, usually into capsules. Based on its pharmacological mode of action, valerian root has been demonstrated to possess sedative and anxiolytic effects.
Because of valerian's historical use as a sedative, anticonvulsant, migraine treatment and pain reliever, most basic science research has been directed at the interaction of valerian constituents with the GABA neurotransmitter receptor system. These studies remain inconclusive and all require independent replication. The mechanism of action of valerian in general, and as a mild sedative in particular, remains unknown. Valerian extracts appear to have some affinity for the GABAA receptor, a class of receptors on which benzodiazepines are known to act. Valerian also contains isovaltrate, which has been shown to be an inverse agonist for adenosine A1 receptor sites. This action likely does not contribute to the herb's sedative effects, which would be expected from an agonist, rather than an inverse agonist, at this particular binding site. Hydrophilic extractions of the herb commonly sold over-the-counter, however, probably do not contain significant amounts of isovaltrate.
Valerian is used for insomnia and other disorders as an alternative to benzodiazepine drugs, and as a sedative for nervous tension, hysteria, excitability, stress and intestinal colic or cramps. In the United States, valerian is sold as a nutritional supplement. Therapeutic use has increased as dietary supplements have gained in popularity, especially after the Dietary Supplement Health and Education Act was passed in 1994. This law allowed the distribution of many agents as over-the-counter supplements, and therefore allowed them to bypass the regulatory requirements of the Food and Drug Administration (FDA). Valerian is used for sleeping disorders, restlessness and anxiety, and as a muscle relaxant. Certain data suggests that Valerian has an effect that is calming but doesn't cause sleepiness the following day. When used as a sleeping aid, valerian appears to be most effective on users who have difficulty falling asleep. Also noteworthy is that valerian has been shown to have positive results on users who wake up during the night. Valerian often seems only to work when taken over longer periods (several weeks), though some users find that it takes effect immediately. Some studies have demonstrated that valerian extracts interact with the GABA receptors. Valerian is also used traditionally to treat gastrointestinal pain and irritable bowel syndrome. However, long term safety studies are absent. Valerian is sometimes recommended as a first-line treatment when risk-benefit analysis dictates. Valerian is often indicated as transition medication when discontinuing benzodiazepines. Valerian has uses in herbal medicine as a sedative. Results of investigations into its effectiveness have been mixed. It has been recommended for epilepsy, but that is not supported by research (although valproic acid—an analogue of one of valerian's constituents, valeric acid—is used as an anticonvulsant and mood-stabilizing drug). Valerian root generally does not lose effectiveness over time.