How Ketamine Infusion Therapy Works
A clinical explanation of the mechanism of action, neurobiological rationale, and what happens during an infusion — written by a consultant psychiatrist.
Educational Content — Not Personal Medical Advice
This article is for educational purposes. It does not constitute medical advice or a recommendation for treatment. Ketamine infusion therapy requires a consultant-led assessment before it can be offered. Always consult a qualified healthcare professional regarding your individual circumstances.
Written by Dr Wayne Kampers, Consultant Psychiatrist, Neuro Reset Clinic
Last reviewed: March 2026
The Neuroscience Behind Ketamine's Antidepressant Effect
Ketamine is classified as a dissociative anaesthetic, first developed in the 1960s. Its psychiatric applications emerged from the observation that patients receiving it for anaesthetic purposes often reported significant improvements in mood — sometimes profound and rapid in nature.
The mechanism responsible for this is now well characterised. Ketamine is a non-competitive antagonist of the NMDA (N-methyl-D-aspartate) glutamate receptor. By blocking these receptors — which play a central role in synaptic plasticity and excitatory neurotransmission — ketamine triggers a cascade of downstream neurobiological events that conventional antidepressants do not.
The Glutamate Hypothesis of Depression
Most antidepressants prescribed today act on the monoamine neurotransmitter systems — primarily serotonin (SSRIs/SNRIs) or noradrenaline. These mechanisms take weeks to weeks to produce adaptive changes sufficient to generate clinical benefit.
Research over the past two decades has identified glutamate dysregulation — particularly involving the NMDA receptor — as a key factor in treatment-resistant depression and PTSD. The glutamate system is the brain's primary excitatory neurotransmitter system and plays a fundamental role in synaptic plasticity: the brain's ability to form and strengthen neural connections.
In treatment-resistant conditions, this synaptic plasticity appears to be impaired. Ketamine's blockade of the NMDA receptor rapidly restores elements of this plasticity through several mechanisms:
- Increased BDNF release: Ketamine rapidly elevates brain-derived neurotrophic factor (BDNF), a protein essential for neuronal survival, growth, and synaptogenesis.
- mTOR pathway activation: This promotes the formation of new synaptic connections in the prefrontal cortex and other regions implicated in mood regulation.
- Burst firing disinhibition: By blocking NMDA receptors on inhibitory interneurons, ketamine permits rapid bursts of glutamate release that further stimulate neuroplasticity pathways.
The net result is a rapid — often within hours — improvement in mood, cognitive flexibility, and emotional processing in many patients. This speed is clinically unprecedented among available antidepressant interventions.
Why is IV Administration Used?
Intravenous (IV) administration ensures:
- Precise dose control — the exact plasma concentration can be regulated, adjusted, and maintained throughout the infusion.
- 100% bioavailability — unlike oral or nasal routes, IV delivery bypasses first-pass metabolism entirely.
- Rapid onset and offset — the effects of IV ketamine appear quickly and resolve within a predictable timeframe, facilitating safe, monitored discharge.
- Protocol consistency — standardised IV protocols allow for reproducible, evidence-based treatment delivery.
What Happens During a Ketamine Infusion
During each session at our London ketamine clinic, patients may experience:
Dissociative sensations
A sense of detachment from the body or environment — typically described as dreamlike or floaty. These are expected, transient, and resolve within the recovery period.
Perceptual changes
Altered time perception, changes in sound or light sensitivity, or mild visual phenomena. These are part of the sub-anaesthetic experience and are not considered hallucinations at therapeutic doses.
Transient cardiovascular changes
A moderate, temporary rise in blood pressure and heart rate is common and is continuously monitored by clinical staff throughout every infusion.
Emotional shifts
Some patients report a sense of calm, or the emergence of thoughts or feelings that feel accessible in new ways. This is considered therapeutically valuable and is why psychological support is integrated into the overall treatment plan.
All experiences during the infusion are entirely expected within the clinical context and resolve as the ketamine clears. Our clinical staff are present throughout to provide reassurance and monitor safety.
The Role of Psychological Integration
Ketamine's neuroplastic effects create a window of enhanced learning and emotional processing. This is why — at Neuro Reset Clinic — ketamine infusion therapy is embedded within a broader care plan that includes psychological support. The therapeutic effects of ketamine can be maximised when patients engage in psychological work during and after the treatment course.
This integrated approach is a defining feature of a responsibly governed ketamine clinic, as distinct from services that offer IV infusions without broader clinical context.
Ready to Find Out if You Are Eligible?
Our ketamine infusion therapy page explains the full treatment pathway, eligibility criteria, costs, and governance framework. To begin the assessment process, complete our free eligibility questionnaire.
Frequently Asked Questions
Conventional antidepressants act on monoamine systems and require weeks of neuroadaptation. Ketamine acts directly on NMDA glutamate receptors, triggering rapid downstream cascades — including BDNF release and synaptogenesis — that produce antidepressant effects within hours in many patients.
At sub-anaesthetic therapeutic doses, ketamine produces dissociative perceptual experiences — a sense of detachment, altered time perception, or mild visual changes — rather than true hallucinations. These are transient, expected, and resolve within the post-infusion recovery period. They are managed by trained clinical staff throughout.
Response durability varies between individuals. Some patients experience sustained benefit following a standard six-session course; others require maintenance infusions to preserve gains. Post-course consultant review assesses response and guides longer-term care planning.
Related reading: Ketamine clinic London — full treatment guide | Ketamine clinic London — clinic overview | Who is eligible for ketamine treatment? | Private ketamine treatment: safety & expectations
Written and reviewed by Dr Wayne Kampers, Consultant Psychiatrist, Neuro Reset Clinic — March 2026.
Interested in Ketamine Infusion Therapy in London?
Our eligibility questionnaire is the first step. Our clinical team will review your answers and contact you to discuss the most appropriate pathway.