Central stimulants are substances that increase brain activity, alertness, and energy levels. The antonyms for central stimulants include sedatives, depressants, and tranquilizers. Sedatives are drugs that have a calming effect on the body, making individuals feel relaxed and sleepy. Depressants, also known as downers, are drugs that slow down brain activity, resulting in decreased energy and increased relaxation. Tranquilizers are medications that reduce anxiety and promote calmness. These substances are often prescribed to treat conditions such as anxiety disorders, insomnia, and seizure disorders. While central stimulants can have beneficial effects, the negative consequences of their use can include addiction, anxiety disorders, sleep disturbances, and increased heart rate and blood pressure.