Skullcap contains scutellarin, a flavonoid with sedative and antispasmodic properties. This substance was probably the active ingredient in the skullcap extract used in 19th-century medicine for nervous disorders ranging from insomnia to epilepsy. It is still used in modern herbal medicine for the prevention of epileptic seizures. More cautious pharmacological opinion concedes as "posible" the validity of skullcap's use as a sedative, but only on the basis of animal tests.
Large doses may cause giddiness, confusion, twitching and stupor.