How is ketamine similar to PCP (Phencyclidine)?

Ketamine and PCP (known as angel dust or Sherm) both function as dissociative anesthetics, sharing a similar broad mode of action in the brain, though their reputations and common uses have diverged.

How effective are traditional antidepressant drugs like SSRIs and Wellbutrin?

Drugs like SSRIs (e.g., Prozac, Zoloft) and Wellbutrin (Bupropion) only provide relief for about 40% of depressed individuals, often come with significant side effects (like libido changes or appetite shifts), and can take weeks or months to show effects.

What is the NMDA receptor and its role in neuroplasticity?

The NMDA receptor acts as an 'and gate' for neuroplasticity, only activating under conditions of unusually high or frequent neural activity. Its activation allows neurons to adapt and change, making behaviors or learning more efficient over time.

How does ketamine, an NMDA receptor blocker, actually increase neuroplasticity?

Ketamine paradoxically increases neuroplasticity by binding to NMDA receptors on inhibitory neurons, reducing their activity. This 'silences' the brakes on excitatory neurons, allowing them to 'burst' fire, which is the perfect pattern for inducing long-term neural circuit changes and mood improvements.

What role does BDNF (Brain-Derived Neurotrophic Factor) play in ketamine's antidepressant effects?

BDNF is a crucial growth factor, and ketamine-induced burst firing of neurons triggers its release. BDNF then promotes neuroplasticity, strengthens neural connections, and helps elevate mood. There is also evidence that ketamine may directly mimic BDNF's action in the brain.

Does ketamine's effect involve the opioid system?

Yes, ketamine affects the opioid pathway. Its metabolite, hydroxynorketamine (HNK), specifically activates mu opioid receptors. Studies show that blocking the opioid system with Naltrexone eliminates ketamine's antidepressant effects, indicating the opioid system is critical for its mood-lifting properties.

What is a 'k-hole' in scientific terms and what are its dangers?

A 'k-hole' is the subjective experience when someone takes enough ketamine to transition into a pseudo-anesthetized state, beyond mild dissociation, bordering on full anesthesia. This can be dangerous, potentially leading to unconsciousness, seizures, or death, especially when combined with other sedatives like alcohol.

Are 'microdosing' ketamine for depression effective?

As of current published clinical evidence, there is no scientific support for the effectiveness of microdosing ketamine for depression. All positive effects for depression relief have been observed with typical clinical dosages (e.g., 0.5 mg/kg body weight) or their oral/sublingual equivalents.

How do different forms of ketamine (R, S, SR) compare in terms of potency?

Clinical trials suggest the combined SR form of ketamine is the most potent for relieving depressive symptoms, followed by the S form (esketamine), which is commonly prescribed. The R form (arketamine) appears to be the least potent and effective.

Key Moments

Ketamine: Benefits and Risks for Depression, PTSD & Neuroplasticity | Huberman Lab Podcast

Andrew Huberman

Science & Technology3 min read103 min video

Aug 7, 2023|588,126 views|12,304|1,557

andrew huberman huberman lab podcast huberman podcast dr. andrew huberman neuroscience huberman lab andrew huberman podcast the huberman lab podcast science podcast ketamine depression treatment ketamine therapy

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Key Moments

TL;DR

Ketamine: Benefits for depression/PTSD, risks, neuroplasticity, opioid effects, and dosage.

Key Insights

Ketamine is a dissociative anesthetic with proven clinical benefits for depression, PTSD, and suicidality, but also a high potential for abuse.

Its antidepressant effects appear to stem from multiple rapid and longer-term mechanisms involving neuroplasticity, potentially including NMDA receptor modulation and BDNF release.

While NMDA receptor blockade is a primary mechanism, its effect on inhibitory neurons paradoxically increases excitatory activity, promoting plasticity in mood circuits.

Ketamine's therapeutic effects may also significantly involve the endogenous opioid pathway, with evidence suggesting its metabolite, HNK, may be crucial for antidepressant action.

Dosage, route of administration (injection, oral, sublingual), and individual metabolism significantly influence ketamine's effects, from mild dissociation to full anesthesia.

The 'k-hole' refers to a state of pseudo-anesthesia achieved at higher ketamine doses, which can be dangerous, especially when combined with other sedatives.

KETAMINE: A DUAL-FACED COMPOUND

Ketamine, a compound with effects similar to PCP, is recognized for its clinical utility in treating severe depression, PTSD, and suicidality. However, it also carries a significant potential for abuse and addiction. This duality necessitates a careful examination of both its therapeutic benefits and associated risks, particularly concerning its profound impact on brain circuitry and consciousness. Its clinical application has surged in recent years due to evolving understandings of mental health and treatment limitations of traditional antidepressants.

MECHANISMS OF ACTION AND NEUROPLASTICITY

Ketamine's primary mechanism involves blocking NMDA receptors, which are crucial for neuroplasticity. Paradoxically, this blockade, particularly on inhibitory neurons, leads to increased excitatory activity in mood-related circuits. This burst firing pattern is thought to trigger the release of BDNF (Brain-Derived Neurotrophic Factor), a key molecule for neuronal growth and synaptic strengthening, thereby enhancing neuroplasticity and promoting long-term mood regulation.

THE ROLE OF THE OPIOID PATHWAY

Beyond NMDA receptor modulation, ketamine also interacts with the endogenous opioid system. Its metabolite, hydroxy norketamine (HNK), shows a particular affinity for mu-opioid receptors. Studies suggest that blocking these opioid receptors can attenuate ketamine's antidepressant effects, indicating the opioid pathway plays a significant role in its therapeutic actions, potentially contributing to both immediate mood elevation and dissociative states.

CLINICAL APPLICATIONS AND DOSAGE CONSIDERATIONS

Clinically, ketamine is used at sub-anesthetic doses (e.g., 0.5 mg/kg intravenously) to provide rapid relief from depression, which can occur within minutes to hours and last for days. Standard treatment often involves multiple sessions over several weeks to achieve durable effects. Less common but potentially effective forms include R-ketamine, S-ketamine, and the racemic SR-ketamine mixture, with S-ketamine and SR-ketamine generally showing greater efficacy and less dissociation.

DISSOCIATIVE STATES AND THE 'K-HOLE'

Ketamine induces dissociative states, characterized by feelings of detachment from one's body and reality, often described as dream-like or observing oneself from a third-person perspective. This is associated with a shift in brainwave patterns towards theta rhythms. A 'k-hole' refers to a state of pseudo-anesthesia achieved at higher doses, which can be dangerous and is often sought recreationally. The risk of anesthesia-like states and seizures increases with dosage and combined substance use.

RISKS, ABUSE POTENTIAL, AND DELIVERY METHODS

Ketamine has a high potential for abuse and addiction. Its effects are highly dependent on dosage and route of administration; oral and sublingual routes often require significantly higher doses than injections to achieve comparable effects due to lower bioavailability. While medical supervision is crucial for therapeutic use, recreational use or unsupervised home use carries risks of overdose, dangerous dissociative states, addiction, and potentially seizures, especially when combined with other sedatives like alcohol.

IMPACT ON BRAIN CIRCUITS AND BEHAVIOR

Ketamine therapy is associated with changes in brain circuits involved in mood, reward, and self-reflection, such as the habenula and the mesolimbic reward pathway. It appears to reduce inhibitory input from the habenula (associated with disappointment) to the reward system, making individuals more receptive to positive experiences. This neural rewiring, coupled with the potential for anti-depressive behaviors, reinforces therapeutic outcomes, underscoring that while drugs can induce plasticity, behavioral engagement is vital for sustained relief.

Mentioned in This Episode

●Supplements

●Organizations

●Books

●Concepts

●People Referenced

Ketamine Dosage and Bioavailability by Administration Route

Data extracted from this episode

Administration Route	Dosage Equivalence (for 50mg IV)	Bioavailability (Active Ketamine into Bloodstream)
Intravenous (IV) / Intramuscular (IM)	50mg	100% (reference)
Oral (Pill)	~150mg (3x IV dose)	~25%
Sublingual (Troche)	~200mg (4x IV dose)	~35%

Potency and Effects of Ketamine Forms (R, S, SR)

Data extracted from this episode

Ketamine Form	Potency for Depression Relief	Dissociation at Given Dosage
Combined SR form	Most potent	More dissociation than S form
S form (Esketamine)	Second best	Less dissociation
R form (Arketamine)	Least potent/effective	More dissociation than S form

Common Questions

Clinically, ketamine is used to treat depression, suicidality, and PTSD. Recreationally, it is used for dissociative states, but carries a high potential for abuse and addiction.

Topics

Neuroscience & the Brain Mental Health & Psychology Psychiatric Drugs Depression Treatment Ketamine Therapy Medicine & Clinical PTSD Treatment Opioid System Dissociation Theory

Mentioned in this video

People

Andrew Huberman

Professor of Neurobiology and Ophthalmology at Stanford School of Medicine and host of the Huberman Lab podcast.

Stanford Medicine

The institution where Andrew Huberman is a professor and where research on ketamine for depression is conducted.

Concepts

NMDA receptor

A receptor critical for neuroplasticity and brain changes, which ketamine blocks. Its activation acts as an 'and gate,' requiring high/unusual electrical activity and glutamate.

Neocortex

The lumpy outside part of the brain associated with action planning, sensory perception, and speech generation; its uncoupling from subcortical regions is linked to ketamine's dissociative effects.

Drugs & Medications

Memantine

An NMDA receptor blocker used to treat Alzheimer's disease, but noted to have no antidepressant effects, contrasting with ketamine's action.

PCP

A dissociative anesthetic similar to ketamine, known by street names like angel dust or Sherm, historically associated with violence and drug abuse.

HNK

A metabolite of ketamine that is selectively activating the opioid system, playing a critical role in the antidepressant effects of ketamine.

psilocybin

A compound that can induce neuroplasticity to relieve major depression, which was covered in a previous podcast episode.

Ketamine

A compound used clinically for depression, suicidality, and PTSD, but also commonly abused recreationally. It is a dissociative anesthetic.

Naltrexone

A drug used to block the opioid receptor pathway, which when administered with ketamine, prevents ketamine's antidepressant effects, suggesting opioid system involvement.

MDMA

A compound capable of inducing relief for PTSD, also discussed in a previous podcast episode.

Prozac

An SSRI (selective serotonin reuptake inhibitor) mentioned as a treatment for depression, which increases serotonin levels.

Zoloft

An SSRI that increases serotonin, used to treat depression, but often associated with side effects and ineffective for many patients.

bupropion

A drug that increases dopamine and norepinephrine, used for depression, but like SSRIs, has side effects and isn't effective for all.

Books

Anti-depressant Effects of Ketamine in Depressed Patients

A landmark paper published around 2000, which was one of the first studies on ketamine for treating depression, showing rapid and persistent relief.

Supplements

AG1

A vitamin, mineral, and probiotic drink with adaptogens, designed to meet foundational nutrition needs and improve focus and energy.

Element

An electrolyte drink containing sodium, magnesium, and potassium without sugar, crucial for cellular and neural function, especially during physical activity or sweating.