Scutellaria lateriflora is one of 90 species in the genus Scutellaria distributed throughout temperate and tropical regions. Most Scutellaria species thrive in garden soils (particularly soils with sunny, open borders) and generally die off after two or three years. Many of the closely related species in this genus are found in the United States. Although Scutellaria lateriflora is native to North America, it is now widely cultivated in Europe. This particular species is also called mad-dog skullcap because of its traditional use in treating hydrophobia.

Scutellaria lateriflora is slightly astringent and widely touted as a nervine. Its tonic, sedative, and antispasmodic activities are reportedly so pronounced that it has long been hailed as an effective therapy for hysteria, convulsions, hydrophobia, and epilepsy. Among its other varied uses are as a treatment for rickets, neuralgia, pain, hiccough, nervous headaches, and headaches associated with incessant coughing.

Despite these popular uses, precise structure-activity relationships have not been determined for skullcap. Even though flavonoids are presumably responsible for many of its purported pharmacological effects, therapeutic claims for Scutellaria lateriflora have not been fully substantiated scientifically.

Skullcap has in the past been frequently adulterated with Teucrium species, a group of plants known to contain potential liver toxins. Because of its possibility for causing serious adverse side effects, including hepatotoxicity and hepatitis, skullcap should not be used unless taken under the direct supervision of a qualified health care practitioner knowledgeable about this plant, and care should be taken to buy the herb from a reliable source.

Scutellaria lateriflora is a slender, perennial, herbaceous plant that grows to a height of 60 cm. Although its erect stem is heavily branched, it is rarely shrubby. Skullcap is distinguished by a thick cover of simple and glandular hairs. Its leaves are typically ovate to lanceolate and petioled, with either complete or scalloped margins.

Skullcap blooms in July, giving rise to barely conspicuous blue and sometimes pink flowers that take the form of short lateral false spikes. The fluffy calyx (sepals) is flattened with two rounded, complete lips. The upper and lower sides of the calyx have different appearances. The flowers have four ascending stamens, each with a pair of cilated anthers. The fruit consists of a warty nut that is globular to flattened-ovoid in shape.

Herb (1 to 2 year-old plant harvested in early summer).

Flavonoids (apigenin, hispidulin, luteolin, scutellarein, scutellarin [bitter glycoside]); catalpol; volatile oils (limonen, terpineol [monoterpenes], d-cadinene, caryophyllene, trans-B-farnesene, B-humulene [sesquiterpenes]); other constituents (lignin, resin, tannin).

Note: Published findings on the constituents of Scutellaria lateriflora are quite limited.

Available for internal use as a powder or liquid extract made from the pulverized herb.

Traditional uses: epilepsy, chorea, hysteria, nervous tension, convulsions, hydrophobia, grand mal or St. Vitus's dance (epileptic seizure), nervous headaches, neuralgia, pain, hiccough, rickets, headache arising from incessant coughing.

Uses of Scutellaria baicalensis roots in Traditional Chinese Medicine: inflammation, suppurative dermatitis, allergic diseases, hyperlipidemia, atherosclerosis.

Conditions: historically used to treat hysteria, nervous tension, epilepsy, chorea, and other nervous disorders; also once used as bitter tonic and febrifuge (for fever).

Clinical applications: nervousness, anxiety, muscle spasm, nervous tics, restless legs syndrome, and mild Tourette's syndrome

Scutellaria latiflora reportedly possesses sedative, antispasmodic, and anti-inflammatory activities as well as inhibitory effects against lipid peroxidation. However, relatively little research has been conducted on Scutellaria lateriflora, and no in vivo data have been located for this species.

Pharmacological studies have been conducted on the root of a related species, Scutellaria baicalensis. Flavonoid compounds in Scutellaria baicalensis are responsible for several in vitro effects, including blockage of mast cell histamine release comparable to that of disodium cromoglycate; inhibition of lipid peroxidation; and inactivation of lipoxygenase and cyclo-oxygenase pathways.

Flavonoids may also account for certain in vivo activities of Scutellaria baicalensis such as hypocholesterolemia in rats. This latter activity has been associated with flavonoid-induced in vitro prevention of experimentally-induced hyperlipidemia and lipolysis, as well as flavonoid-induced in vitro lipogenesis in adipose tissues.

In certain animal investigations, Scutellaria baicalensis did not elicit a marked effect on blood pressure in cats and rabbits. Nor did it exert CNS depressant or antispasmodic action on test animals. However, Scutellaria baicalensis did exhibit antibacterial effects against several strains of Gram-positive bacteria. It is not clear, however, if these findings are relevant to the pharmacological effects of Scutellaria lateriflora.

In clinical trials conducted in China, scutellarin, the active constituent in several Scutellaria species, was administered i.m., i.v., or p.o. to over 600 patients diagnosed with cerebral thrombosis, cerebral embolism, and paralysis. An overall rate of efficacy of 88% was reported for this treatment.

• Dried herb: 1 to 2 g or by infusion tid
• Fluid extract (1:1 in 25% alcohol): 2 to 4 ml tid
• Tincture (1:2 in 35% alcohol): 2 to 5 ml tid

According to some authorities, skullcap is devoid of side effects when taken in recommended therapeutic dosages. However, other experts warn that because of the possibility of adulteration, skullcap should be used with caution.

Overdosage of skullcap tincture produces symptoms of giddiness, stupor, mental confusion, seizure, twitching of the limbs, intermission of the pulse, and epileptic-related manifestations. Oral intake of skullcap may be associated with hepatotoxic reactions, probably attributable to adulteration with Teucrium species, for example, Teucrium chamaedrys (germander).

Skullcap should be avoided under all circumstances during pregnancy and lactation due to potential adulteration and subsequent liver toxicity.

While no clinically significant interactions between this herb and conventional medications are known to have been reported in the literature to date, skullcap does possess sedative properties; therefore, it should be used with caution, if at all, in patients taking benzodiazepines, barbiturates, or other medications with sedative potential.

Skullcap is an entry on the General Sales List in Great Britain. In the USA, the FDA designates skullcap as herb of undefined safety. This plant is not used in food products.

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