Nootropic - Wikipedia - en.wikipedia.org  ## Metadata - Author: **en.wikipedia.org** - Full Title: Nootropic - Wikipedia - Category: #articles - Tags: #health - URL: https://en.wikipedia.org/wiki/Nootropic#Availability_and_prevalence ## Highlights - Nicotine – a meta-analysis of 41 clinical studies concluded that nicotine administration or smoking improves alerting and orienting attention and episodic and working memory and slightly improves fine motor performance - A 2016 review reported that theanine may increase alpha waves in the brain. Alpha waves may contribute to a relaxed yet alert mental state.[50] Another study has shown that an oral administration of theanine at doses of 50–200 mg promoted "relaxation without causing drowsiness" within 40 mins after consumption.[51] A 2014 systematic review and meta-analysis found that concurrent caffeine and L-theanine use had synergistic psychoactive effects that promoted alertness, attention, and task switching. These effects were most pronounced during the first hour post-dose - Racetams, such as piracetam, oxiracetam, phenylpiracetam, and aniracetam, are often marketed as cognitive enhancers and sold over the counter.[52] A 2019 study found that piracetam supplements sold in the United States were inaccurately labeled.[52] Racetams are often referred to as nootropics, but this property is not well established.[53] The racetams have poorly understood mechanisms, although piracetam and aniracetam are known to act as positive allosteric modulators of AMPA receptors and appear to modulate cholinergic systems