The inner anhydrid or lactone of santonic acid obtained from santonica.

Properties : Santonin occurs as colorless, rhombic prisms, odorless and nearly tasteless when first put into the mouth, but afterward developing a bitter taste. It is very insoluble in water (1:5,300), and soluble in alcohol (1:35).

Action and Uses: Santonin is used for its poisonous action on intestinal parasites. It is seldom absorbed to a sufficient extent to produce symptoms. When this occurs, the chief effects are yellow vision and epileptiform convulsions,

It is used especially for its effect on roundworms. In proper doses it is a reasonably safe drug. It is frequently administered with calomel.

Dosage: 0.065 gm. or 1 grain.

As absorption is to be avoided the remedy is preferably administered in the form of coarse crystals, either inclosed in a capsule or made up into a lozenge rather than in finely powdered form. The soluble sodium santoninate should be avoided as a vermifuge.