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

TL;DR

This paper proposes a new oral antidepressant regimen using existing drugs to mimic ketamine's effects without its drawbacks.

Contribution

The novel contribution is a four-drug regimen combining DXM, CYP2D6 inhibitors, piracetam, and glutamine for rapid antidepressant effects.

Findings

DXM provides NMDA antagonism similar to ketamine's initial action.

CYP2D6 inhibitors may prolong DXM's effectiveness when combined.

Piracetam and glutamine could enhance synaptic plasticity and prevent excitotoxicity.

Abstract

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.

Figures