Psychotropic drug, in pharmacology, any agent that induces changes in awareness, behaviour, mood, perception, or sensation. Most psychotropic drugs are classified as one of five different types: antianxiety agents, antidepressants, antipsychotics, hypnotics, or mood-stabilizing drugs. Psychotropic drugs are used to treat a broad array of conditions, from sleep disorders and pain to anxiety, depression, and psychosis.Psychotropic drugs exert their actions by either mimicking the effects, blocking the activity, or altering the storage, release, or uptake of neurotransmitters (signaling molecules in the brain that relay information between neurons and between neurons and other types of cells). Some psychotropic drugs restore the balance of neurotransmitters by preventing their breakdown once released from neurons. Examples of neurotransmitters that can be affected by psychotropic drugs include dopamine, gamma-amino butyric acid (GABA), norepinephrine, and serotonin.