LSD (lysergic acid diethylamide). Molecular model of LSD (also called lysergide), a potent hallucinogenic and mood-altering drug. LSD was first synthesised in 1938 from lysergic acid, an alkaloid drug found in the ergot fungus that grows on grains of rye. The drug has no proven medical uses but is widely abused for the dream-like changes in mood and thought that it causes. Users can experience anything from feelings of omnipotence to extreme terror. These feelings can possibly lead to irrational behaviour which may endanger the user's life. Side-effects include drowsiness, dizziness, dilated pupils, numbness and tingling, weakness, tremors, and nausea.