Scullcap

Scientific Name(s): Scutellaria lateriflora L.
Common Name(s): Helmetflower, Hoodwort, Mad-dog weed, Scullcap, Skullcap

Medically reviewed by Drugs.com. Last updated on Aug 16, 2023.

Clinical Overview

Use

Scullcap traditionally has been used as a sedative for nervousness and anxiety, although data are limited to support this use. Benefit for mood disturbance has also been demonstrated.

Dosing

Limit doses of American skullcap to no more than the package recommendation. Typical doses (see individual product information): Dried herb: 1 to 2 g 3 times/day; Tea: 240 mL 3 times/day (pour 250 mL of boiling water over 5 to 10 mL of the dried herb and steep for 10 to 15 minutes); Tincture: 2 to 4 mL 3 times/day. Mood disturbance: 350 mg capsules consisting of freeze-dried S. lateriflora whole aerial parts (not a standardized extract) given 3 times daily for 2 weeks.

Contraindications

Contraindications have not yet been identified.

Pregnancy/Lactation

Documented adverse effects in pregnancy. Avoid use. May inhibit pituitary and chorionic gonadotropins, as well as prolactin.

Interactions

None well documented, though it may exaggerate the effects of other drugs that cause drowsiness.

Adverse Reactions

If taken according to the manufacturer's directions, scullcap does not seem to exhibit any adverse effects. Minor and infrequent side effects have been reported from a small clinical trial including vivid dreams, feeling spaced out, and mild digestive disturbances.

Toxicology

An overdose of the tincture causes giddiness, stupor, confusion, twitching of the limbs, intermission of the pulse, and other symptoms similar to epilepsy.

Scientific Family

• Lamiaceae (mint)

Botany

Scullcap (S. lateriflora), a member of the mint family, is native to the United States where it grows in moist woods. Although it is widely distributed throughout large regions of North America, there are related species found as far away as China. There are over 300 species of Scutellaria worldwide. Common scullcap (Scutellaria lateriflora) is the best known of these species.

Scullcap is an erect perennial that grows to 1 m in height. Its bluish flowers bloom from July to September. Official compendia recognize only the dried overground portion of the plant as useful; however, some herbal texts list all parts as medicinal.(Meyer 1934) The aerial parts of the plant are collected during the flowering period, typically August and September. It is important to note the difference between American skullcap (S. lateriflora) and S. baicalensis (otherwise known as Chinese skullcap), which is a related plant.(Wolfson 2003) The members of this diverse genus are not generally interchangeable.(Wolfson 2003) A number of species have been used medicinally, and the most common European variety is S. baicalensis, a native of East Asia (see Baical Skullcap monograph).

Related/similar drugs

turmeric, Ginkgo Biloba

History

Scullcap appears to have been introduced into traditional American medicine toward the end of the 1700s, when it was called mad-dog skullcap because of its use as a treatment for rabies. It was later used as a tonic, particularly in proprietary remedies for "female weakness."(Tyler 1987) The plant was reputed to be an herbal tranquilizer, particularly in combination with valerian, but has fallen into disuse.

Scullcap has traditionally been used to treat nervousness, irritability, and neuralgia, as well as for its sedative properties.

Chemistry

The various species of Scutellaria contain several flavonoid glycoside pigments. These include scutellarein, wogonin, isoscutellarein, and baicalin. A diterpenoid (scuterivulactone) has also been identified.(Kizu 1987)

The aboveground parts of S. lateriflora have been found to contain neoclerodane diterpenes(Bruno 1998) flavones, and flavone glucuronides.(Gafner 2003) The flavonoids include baicalin, lateriflorin, dihydrobaicalin, and baicalein, which were quantitatively determined by liquid chromagraphy with ultraviolet detection/MS, and thin-layer chromatography. Adulteration of S. lateriflora with species of germander was detected by microscopy and by the presence of phenylpropanoids such as teucreoside, which were not found in scullcap.(Gafner 2003)

Uses and Pharmacology

Sialic acids are widely distributed in tissues as constituents of glycolipids and glycoproteins. They are present in mucus secretions and cell membranes where they are thought to be the sites at which viruses attach and penetrate the cell wall. Serum sialic acid is known to increase in certain disease states (eg, cancers, rheumatic diseases, infections, inflammations), and it has been postulated that an inhibitor of sialidase, such as scullcap extract, may have a therapeutic application.

Most research to date focused on the baical skullcap (S. baicalensis), which is used to treat inflammation and atherosclerosis, has antibacterial, antiviral, antioxidant, and antithrombic properties. Few studies have been carried out on S. lateriflora and further work is needed on this species.

Anxiolytic

Animal data

One study assessed the anxiolytic efficacy of S. lateriflora in 2 animal test models to verify the traditional claims of anxiolytic activity. The results of the behavioral test indicated effects on anxiety levels in rats. The results of the study indicate that S. lateriflora has multiple active compounds and warrants further study to determine its potential to become a popular anxiolytic phytomedicine.(Awad 2003)

Clinical data

A double-blind, placebo-controlled study in 19 healthy volunteers aimed to clarify the effectiveness of S. lateriflora in reducing anxiety. Subjective end points were used and assessed the effects of the preparations on patients' energy, cognition, and anxiety. A greater degree of sedation was seen at higher doses. The data produced indicate an anxiolytic property of S. lateriflora in comparison to placebo.(Wolfson 2003)

Antimicrobial

Teas prepared from Scutellaria species have demonstrable in vitro antibacterial and antifungal activity.(Franzblau 1986)

Comparison studies with other herbal anxiolytics and prescription medicines are needed to define more specifically the clinical potential of S. lateriflora as an anxiety treatment. Further studies are needed to validate the results of limited studies and subjective end points used. Clinically validated endpoints are needed in clinically impaired populations to further determine the clinical effect of S. lateriflora.

Mood

Clinical studies

The effect of scullcap on mood was assessed in 31 healthy volunteers (6 men) 19 to 66 years of age who were randomized to 350 mg of S. lateriflora (whole aerial parts, not a standardized extract) 3 times daily or placebo for 2 weeks in a double-blind fashion and then crossed over to other treatment. Recruitment was generally based on persistent stress, anxiety, mood swings, irritability, poor sleep, or difficulty coping, as well as the inclusion of nonanxious participants. Exclusion criteria included a history of behaviors, conditions, or medications affecting the CNS. Overall, 81% of the group had a Beck Anxiety Inventory (BAI) score of 15 or less, which is considered mildly anxious at most. Although no significant difference was found between treatments measured on BAI scores, changes in total mood disturbance were significantly better with skullcap (P<0.001). Specifically, a significant group × treatment interaction was observed for the Depression-Dejection state and an enhanced effect of skullcap for the Vigor-Activity state with a 20% increase in energy levels. A potential carryover effect for scullcap was further analyzed and a highly significant improvement in total mood disturbance (P<0.001) was observed, an effect not seen with placebo.(Brock 2014)

Skull cap was identified as one of the most common herbs used by certified or licensed midwives for postpartum depression based on state-wide surveys in California, Texas, and North Carolina.(Dennehy 2010)

Dosing

Not enough is known about American skullcap to recommend its use to children younger than 18 years.

No recent well-controlled studies of American skullcap have been carried out in humans. Doses of American skullcap should be limited to no more than the package recommendation.

Typical doses (see individual product information):

• Dried herb: 1 to 2 g 3 times/day.

• Tea: 240 mL 3 times/day (pour 250 mL of boiling water over 5 to 10 mL of the dried herb and steep for 10 to 15 minutes).

• Tincture: 2 to 4 mL 3 times/day.

Pregnancy / Lactation

Documented adverse effects. Avoid use. May inhibit pituitary and chorionic gonadotropins, as well as prolactin.(Ernst 2002)

Skull cap was identified as the most common single herb used by certified or licensed midwives for labor-related anesthesia or analgesia based on state-wide surveys in California, Texas and North Carolina.(Dennehy 2010)

Interactions

None well documented. However, because American skullcap may promote sleepiness, it may intensify the effects of drugs that also cause drowsiness. The effects of the drug may be exaggerated, resulting in sedation or mental impairment.

Adverse Reactions

The FDA presently designates scullcap as a herb of undefined safety.(Awad 2003) Minor and infrequent side effects were reported with the treatment for mood, and included vivid dreams (n=1), feeling spaced out (n=1), mild digestive disturbances (n=4), and a constant taste of salt (n=1). Of the 26 participants who completed a symptom diary, the conditions that reportedly resolved or improved corresponded with some of those noted for S. lateriflora related to allergies, inflammation, anxiety-related digestive problems, muscle tension and pain, headaches, and menstrual-related problems.(Brock 2014) A case of hypotension has been reported.(Dennehy 2010)

Toxicology

According to the FDA, an overdose of the tincture causes giddiness, stupor, confusion, twitching of the limbs, intermission of the pulse, and other symptoms indicative of epilepsy.(Duke 1985) Exceptionally large doses have resulted in seizure-like movements.

No data exist demonstrating liver toxicity on an experimental basis, or with any of the scullcap species as a solitary medicament.(Wolfson 2003) Other species of the genus have been implicated in reported cases of hepatotoxicity.

Index Terms

• Scutellaria baicalensis
• Chinese skullcap

References

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