Cocaine: obtained from Erythroxylum coca, generally snorted. Causes hallucinations, and has a potent effect on central nervous system, producing a sense of euphoria and increased energy.
Hashish: Obtained from Cannabis plant, taken by inhalation and oral ingestion. Effects on cardiovascular system.
Barbiturates: It is a sedative.
Used as a medicine to help patients cope with mental illness like depression, insomnia etc.
Reduces excitement by depressing the $CNS$ activity and lowers physiological activity leading to drownsiness or sleep