Piracetam

Piracetam (2-oxo-1-pyrrolidineacetamide; CAS 7491-74-9; molecular formula C6H10N2O2; molecular weight 142.16) is the original racetam, synthesized in 1964 by Corneliu Giurgea at UCB Pharma in Belgium and the molecule for which Giurgea coined the term "nootropic" (1972). The compound is a cyclic derivative of GABA but does not bind GABA receptors at therapeutic concentrations; the molecular target is incompletely characterized despite over five decades of clinical use. Proposed mechanisms include modulation of phospholipid membrane fluidity (particularly in aged neurons where membrane fluidity is decreased), enhancement of acetylcholine release through indirect cholinergic effects, modest AMPA receptor positive allosteric modulation at high concentrations, and improved cerebral microcirculation through erythrocyte deformability and platelet aggregation effects. None of these mechanisms is fully sufficient to explain the clinical phenotype. Piracetam is approved in many European, Asian, and Latin American countries (not the United States) for cognitive impairment in elderly patients, post-stroke aphasia, vertigo, dyslexia, breath-holding spells in children, and cortical myoclonus. The plasma half-life is 4 to 6 hours; oral bioavailability is essentially complete; the compound is renally excreted unchanged. Research doses reported in the literature range widely from 1.6 to 9.6 grams, with cortical myoclonus indications at the highest end of the reported range. The safety profile is exceptionally clean; LD50 in rodents is greater than 10 g/kg and serious adverse events in human use are rare. The principal limitations on the clinical evidence base are heterogeneous endpoint selection across trials and the absence of large modern randomized trials that would meet contemporary regulatory standards.