the dried milky juice from plants of the genus Lactuca (family Compositae); resinous yellowish-brown lumps with a bitter taste and an unpleasant odor.

Lactucarium contains as much as 66 percent bitter principles (lactucerin, lactucin, lactucictin), along with traces of alkaloids. It is partially soluble in hot water and organic solvents. Lactucarium is used for therapeutic purposes as a mild somnifacient and analgesic, but it is toxic in large doses.