Hydroxybutyric Acid Lactone, also known as GHB, is a synthetic drug that can cause a dangerous sedative effect. However, its opposite, or antonym, would be a substance that has a stimulating effect on the body and mind. Some examples of these substances would be caffeine, amphetamines, or even marijuana. Caffeine is a common stimulant found in coffee, tea, and energy drinks. Amphetamines are prescribed for conditions like ADHD and narcolepsy, and are known for their ability to increase alertness and attention. Marijuana, although classified as a depressant, can also produce stimulating effects on the brain, such as increased creativity and euphoria.