DXM, CYP2D6-inhibiting antidepressants, piracetam, and glutamine: proposing a ketamine-class antidepressant regimen with existing drugs

Rapid-acting antidepressants show that mood can lift within hours when glutamatergic circuits shift from an “NMDA-dominant” to an “AMPA-dominant” state. Intravenous ketamine achieves this flip but is hampered by dissociation and logistics, while dextromethorphan + bupropion (Auvelity ® ) primarily supplies the initial NMDA blockade and yields slower, less durable benefit. We hypothesize that a fully oral, low-cost, four-component regimen may be able to approximate ketamine’s full plasticity cascade (1) dextromethorphan (DXM) for NMDA antagonism; (2) a potent CYP2D6 inhibitor (fluoxetine, paroxetine, or high-dose duloxetine) to prolong DXM exposure; (3) piracetam as an AMPA positive allosteric modulator; and (4) micronized L-glutamine to restore presynaptic glutamate pools and buffer against excitotoxicity. Preclinical evidence supports mechanistic synergy along the same axis, but the full combination remains untested in humans. This hypothesis warrants formal preclinical and clinical evaluation.