E1R is the (4R,5S) stereoisomer of methylphenylpiracetam that has been shown to have the greatest effect on the modulation of the sigma-1 receptor.[2]
Enantiomers
The two R-configuration enantiomers, i.e. (4R,5S) and (4R,5R), of methylphenylpiracetam are more active positive allosteric modulators of the sigma-1 receptor than the two S-configuration enantiomers, i.e. (4S,5R) and (4S,5S).[1][3]
E1R enhances cognition and has efficacy against cholinergic dysfunction in mice without affecting locomotor activity.[2] Pretreatment with E1R enhanced the σ1R agonist PRE-084's stimulating effect and facilitated passive avoidance retention.[2] It alleviated scopolamine-induced cognitive impairment.[2] The cognition enhancing activity of E1R is higher than that of (R)-phenylpiracetam.[4]
Because E1R had no effect on locomotor activity, it was found to be free of potential motor side effects.[2]
Legality
Australia
Methylphenylpiracetam is a schedule 4 substance in Australia under the Poisons Standard (February 2020).[5] A schedule 4 substance is classified as "Prescription Only Medicine, or Prescription Animal Remedy – Substances, the use or supply of which should be by or on the order of persons permitted by State or Territory legislation to prescribe and should be available from a pharmacist on prescription."[5]
^Veinberg G, Vavers E, Orlova N, Kuznecovs J, Domracheva I, Vorona M, Zvejniece L, Dambrova M (2015). "Stereochemistry of phenylpiracetam and its methyl derivative: improvement of the pharmacological profile". Chemistry of Heterocyclic Compounds. 51 (7): 601–606. doi:10.1007/s10593-015-1747-9. S2CID93449199. In conclusion, the obtained data demonstrated that E1R is the most active memory enhancing enantiomer of the 5-methyl-substituted phenylpiracetam homolog, and its cognition enhancing activity is higher than that of (R)-phenylpiracetam.