Therapeutic Ketamine for Mental Health: Forms, Evidence, and Clinical Considerations

For decades, treatment-resistant depression (TRD) — defined as failure to respond to at least two adequate antidepressant trials — left clinicians with limited options. Ketamine, a dissociative anesthetic first synthesized in 1962 and used medically since the 1970s, has emerged as one of the most significant advances in psychiatric pharmacology in half a century.

What makes ketamine remarkable is speed. While conventional antidepressants require 4–8 weeks to take full effect, ketamine can produce measurable relief within hours. This rapid onset has made it particularly relevant for patients with acute suicidal ideation — a population for which few fast-acting pharmacologic options previously existed.

Yet ketamine is not without complexity. It is a Schedule III controlled substance with abuse potential. Its therapeutic forms vary widely in regulation, oversight, and evidence quality. The clinical community remains split between genuine enthusiasm and warranted caution — a tension that patients seeking treatment should understand clearly.

IV Ketamine Infusions (Racemic Ketamine)

The most extensively studied form in psychiatric research. Administered off-label in specialized clinics, the standard protocol involves 0.5 mg/kg infused over 40 minutes, delivered in a series of six infusions across 2–3 weeks. Patients are monitored for vital signs, dissociative effects, and hemodynamic changes throughout. IV delivery allows precise dose titration and produces the most consistent bioavailability.

Intranasal Esketamine (Spravato)

Esketamine — the S-enantiomer of ketamine — received FDA approval in 2019 for treatment-resistant depression, and subsequently for major depressive disorder (MDD) with acute suicidal ideation or behavior. It is administered as a nasal spray in certified healthcare settings under the REMS (Risk Evaluation and Mitigation Strategy) program. Patients must remain under observation for at least two hours after each dose, and the drug cannot be taken home. Dosing is typically 56 mg or 84 mg, given twice weekly during induction and then weekly or biweekly for maintenance.

Oral and Sublingual Ketamine

Some providers prescribe compounded oral or sublingual ketamine lozenges (troches) off-label, including through telehealth platforms. Bioavailability is lower and more variable (roughly 17–29% for oral, up to 30% sublingual), making dosing less predictable. This route is the most controversial: it carries reduced clinical oversight, higher potential for misuse, and limited controlled trial data supporting its psychiatric efficacy. The 2023 death of actor Matthew Perry — linked to unsupervised ketamine use — intensified scrutiny of at-home prescribing models.

Traditional antidepressants modulate monoamines — serotonin, norepinephrine, dopamine — and require weeks of downstream receptor adaptation before clinical effects appear. Ketamine operates through an entirely different pathway, which explains its rapid onset.

The cascade begins with NMDA receptor antagonism. By blocking NMDA receptors on GABAergic interneurons, ketamine disinhibits glutamatergic neurons, producing a transient surge of glutamate — the brain's primary excitatory neurotransmitter. This glutamate surge activates AMPA receptors, which in turn trigger intracellular signaling cascades involving mTOR (mechanistic target of rapamycin) and the release of brain-derived neurotrophic factor (BDNF).

BDNF promotes rapid synaptogenesis — the formation of new synaptic connections — particularly in the prefrontal cortex and hippocampus, regions where synaptic density is reduced in chronic depression. Animal studies have demonstrated visible increases in dendritic spine density within 24 hours of a single ketamine dose.

In essence, where SSRIs slowly adjust neurotransmitter availability, ketamine rapidly rebuilds the synaptic architecture that depression has degraded. Ketamine also demonstrates anti-inflammatory properties, reducing pro-inflammatory cytokines such as IL-6 and TNF-α — relevant given the well-documented association between neuroinflammation and depressive disorders.

IV ketamine has been studied in over 30 randomized controlled trials for depression. Meta-analytic data show response rates of 60–70% in treatment-resistant depression, with many patients reporting improvement within 4–24 hours of the first infusion. However, durability remains a challenge: without maintenance infusions, the antidepressant effect typically wanes within days to 2–3 weeks. Optimal maintenance schedules are still being established, though many clinics offer booster infusions every 3–6 weeks.

Esketamine (Spravato) earned FDA approval based on multiple Phase 3 trials, including the ASPIRE I and ASPIRE II studies in patients with MDD and suicidal ideation. The number needed to treat (NNT) is approximately 6–8, comparable to many established psychiatric medications. Long-term data from the SUSTAIN trials showed that continued esketamine plus oral antidepressant therapy significantly reduced relapse rates versus discontinuation.

Perhaps the most distinctive finding across both forms is rapid reduction in suicidal ideation — an effect observable within hours and largely unique among psychiatric medications. Standard antidepressants carry FDA black box warnings about potential short-term increases in suicidality; ketamine moves in the opposite direction, acutely and measurably.

Evidence for oral and sublingual ketamine is more limited, consisting primarily of open-label studies and case series rather than rigorous Phase 3 trials.

Ketamine produces dose-dependent dissociative effects that patients should be prepared for. During a typical IV infusion or esketamine session, individuals may experience:

• Perceptual distortions — visual or auditory changes, altered color perception
• Depersonalization or derealization — feeling detached from one's body or surroundings
• Floating sensation — a sense of weightlessness or drifting
• Time distortion — minutes may feel like hours or pass instantly
• Emotional surfacing — unexpected feelings or memories may arise

These effects typically begin within minutes of administration, peak at 20–40 minutes, and resolve within 45–90 minutes. The experience can range from mildly dreamlike to intensely altered, depending on the dose and individual sensitivity.

An emerging body of research suggests the dissociative experience may itself be therapeutically meaningful rather than merely a side effect. Several studies have found correlations between the intensity of dissociation and the magnitude of antidepressant response, though this relationship remains debated. Some clinicians pair ketamine sessions with psychotherapeutic frameworks — so-called ketamine-assisted psychotherapy (KAP) — to leverage the altered state for deeper psychological processing.

Regardless of theoretical orientation, proper set and setting matter. Patients should be in a calm, supportive environment with trained clinical staff.

Abuse and Dependence Potential

Ketamine is a Schedule III controlled substance with known recreational misuse. While the risk of addiction at therapeutic doses under medical supervision appears low, the potential for psychological dependence exists, particularly with less supervised routes of administration. Tolerance can develop with repeated use.

Bladder Toxicity

Chronic ketamine use is associated with interstitial cystitis — a painful inflammatory bladder condition documented extensively in recreational users. At standard psychiatric dosing frequencies, this risk appears minimal, but long-term surveillance data are still limited. Patients receiving ongoing ketamine therapy should be monitored for urinary symptoms.

The At-Home Telehealth Controversy

The rapid expansion of telehealth platforms prescribing oral ketamine for home use has drawn significant criticism. Critics point to reduced clinical oversight, inconsistent patient screening, limited monitoring during administration, and heightened diversion risk. The FDA issued a warning in 2023 about compounded ketamine products, noting reports of adverse events including death. This stands in sharp contrast to the controlled settings required for esketamine administration.

Cost and Access

IV ketamine infusions typically cost $400–$800 per session and are generally not covered by insurance, placing a full course of six infusions at $2,400–$4,800 out of pocket. Esketamine, while more expensive at list price, is covered by most commercial insurers and Medicare, making it more accessible for many patients. Cost remains a significant barrier to equitable access.

Ketamine-based treatments are generally considered for patients who meet specific clinical criteria:

• Treatment-resistant depression — failure of at least two adequate antidepressant trials at appropriate doses and durations
• MDD with acute suicidal ideation — particularly for esketamine, which carries a specific FDA indication
• Severe depression requiring rapid stabilization — as a bridge while longer-term treatments take effect

Ketamine is not a first-line treatment. It is positioned as an option after conventional therapies — including SSRIs, SNRIs, augmentation strategies, and psychotherapy — have proven insufficient.

Contraindications and cautions include:

• Uncontrolled hypertension — ketamine transiently raises blood pressure and heart rate
• Active psychotic disorders — dissociative effects may exacerbate psychotic symptoms
• History of substance use disorder — requires careful risk-benefit analysis given ketamine's abuse potential
• Aneurysmal vascular disease or elevated intracranial pressure
• Pregnancy

The strongest evidence and safest delivery models currently support IV ketamine administered in specialized clinics and esketamine under the FDA REMS program. Patients considering ketamine therapy should seek providers with specific training in ketamine administration and mental health, ideally in settings with established safety protocols and treatment integration plans.