AniracetamvsEmoxypine (Mexidol)

Aniracetam is a positive allosteric modulator of AMPA receptors, binding to the allosteric site and slowing receptor desensitization, which prolongs excitatory postsynaptic currents and facilitates long-term potentiation. It also modulates group II metabotropic glutamate receptors (mGluR2/mGluR3), which regulate presynaptic glutamate release. Uniquely among racetams, aniracetam increases dopamine and serotonin release in the prefrontal cortex via modulation of monoamine transporter activity and vesicular release, contributing to its anxiolytic and mood-enhancing effects. It reduces GABAergic inhibition in the hippocampus through indirect modulation of GABA-A receptors, facilitating NMDA receptor activation and memory consolidation. The lipophilic phenylacetyl group enables rapid blood-brain barrier penetration.

Emoxypine (2-ethyl-6-methyl-3-hydroxypyridine succinate) has a 3-hydroxypyridine structure similar to vitamin B6 (pyridoxine). It is one of the most potent inhibitors of lipid peroxidation in brain tissue — it scavenges hydroxyl radicals and peroxyl radicals, inhibits Fe2+-induced lipid peroxidation, and may chelate transition metals. It modulates the GABA-benzodiazepine receptor complex (GABA-A), enhancing GABAergic transmission through positive allosteric modulation — possibly at a site distinct from the classical benzodiazepine binding site, explaining the lack of sedation and tolerance. It improves mitochondrial function (Complex I protection, membrane stabilization), stabilizes cell membranes (reducing fluidity changes during oxidative stress), and enhances cerebral microcirculation (possibly via nitric oxide or prostaglandin modulation). The anxiolytic mechanism may involve partial agonism or different subunit selectivity.