<unk> , popularly referred to as "smart drugs", "smart nutrients", "cognitive enhancers" and "brain enhancers", is a class of drugs that improve impaired human cognitive abilities (the functions and capacities of the brain).  This article covers all substances, including drugs, nutrients, and herbs, that have purported cognitive enhancing effects.
The word<unk>  was coined in 1964 by the Romanian Dr. Corneliu E. Giurgea, derived from the Greek words noos, or "mind," and tropein meaning "to bend/turn". Typically,<unk> s are alleged to work by altering the availability of the brain's supply of neurochemicals (neurotransmitters, enzymes, and hormones), by improving the brain's oxygen supply, or by stimulating nerve growth.  However the efficacy of alleged<unk>  substances in most cases has not been conclusively determined.  This is complicated by the difficulty of defining and quantifying cognition and intelligence.
Nootropic
Chronotropic
Sympatholytic
Cholinergic
Apocrine
Endothermic
Antineoplastic
Sedative