Ketamine is a dissociative anesthetic that, at sub-anesthetic doses, exerts powerful antidepressant, anxiolytic, and analgesic effects. It is classified as an NMDA receptor antagonist — meaning it blocks a specific receptor in the brain involved in glutamate signaling. Unlike conventional psychiatric medications that work primarily on the serotonin, dopamine, or norepinephrine systems, ketamine’s mechanism is fundamentally different. By modulating glutamate — the brain’s most abundant excitatory neurotransmitter — it triggers a cascade of neuroplastic changes. This process rapidly promotes the growth of new synaptic connections in brain regions associated with mood regulation, particularly the prefrontal cortex and hippocampus. It also increases brain-derived neurotrophic factor (BDNF), a protein essential for neuronal growth and resilience. The result: therapeutic effects that can emerge within hours — not weeks. For patients with treatment-resistant conditions, this speed and efficacy can be life-changing.