Piracetam

Piracetam's mechanism of action is not fully understood, though it influences both neuronal and vascular functions without acting as a sedative or stimulant.¹ The drug is a positive allosteric modulator of the AMPA receptor, although this action is weak and may not fully account for its clinical effects.⁷ Piracetam is also an inhibitor of N-type calcium channels, with an IC50 of approximately 3 μM in rat neurons, well below the central nervous system concentrations achieved at typical doses.⁸ Rather than binding with high affinity to specific receptors, piracetam appears to modulate neurotransmission by interacting with polar heads in phospholipid membranes, stabilizing membrane fluidity and potentially increasing the density and function of postsynaptic receptors including NMDA receptors.⁹ Through this membrane-stabilizing action, piracetam enhances cholinergic neurotransmission via muscarinic acetylcholine receptors and may influence glutamatergic, serotonergic, and noradrenergic systems.¹ GABA brain metabolism and GABA receptors are not affected by piracetam despite its structural similarity to GABA.¹⁰ At the vascular level, piracetam increases erythrocyte deformability, reduces platelet aggregation, diminishes erythrocyte adhesion to vascular endothelium, and reduces capillary vasospasm, collectively improving microcirculation including cerebral blood flow.¹¹¹