Types of Ketamine Therapy Compared: Which Is Most Effective?

What Is Ketamine Therapy?

Ketamine is a medication FDA-approved as an anesthetic since 1970 and included on the World Health Organization List of Essential Medicines since 1985.¹ The term refers to the supervised use of sub-anesthetic doses of ketamine to treat mental health conditions including depression, anxiety, and PTSD.

The medication temporarily modulates glutamate signaling and NMDA receptor activity in the brain. Because it works through these pathways, ketamine creates a window of increased neuroplasticity that allows entrenched thought patterns and neural networks to shift.

There are two primary forms of the medication used in mental health care:

• Racemic ketamine: Contains both S- and R-ketamine enantiomers. It is used in intravenous, intramuscular, sublingual, and subcutaneous forms. Licensed providers prescribe it off-label for mental health conditions, which is a widespread and legally accepted medical practice across psychiatry.²
• Esketamine (Spravato): Uses only the S-enantiomer. It is an FDA-approved nasal spray specifically for treatment-resistant depression and major depressive disorder with suicidal ideation. It must be administered in certified healthcare settings under a Risk Evaluation and Mitigation Strategy (REMS) program.

Ketamine treatment is not a single intervention. It encompasses multiple administration routes, settings, and care protocols. The route matters, but the supervision and integration surrounding each session are equally important.

Types of Ketamine Therapy and How Each Is Given

Five primary administration routes exist for therapeutic ketamine. Each approach features distinct delivery methods, settings, bioavailability profiles, and medical considerations.

Intravenous Ketamine Infusions

Intravenous ketamine delivers the medication directly into the bloodstream through a vein. Sessions typically last over 40 minutes in a clinic or medical office. It has the highest bioavailability of any route at nearly 100%.

The typical in-clinic process involves medical screening, IV placement, continuous vital-sign monitoring, and a post-infusion observation period. Sessions require travel to a certified clinic and the presence of medical staff throughout the appointment. Induction protocols commonly involve a series of infusions over several weeks.

Intravenous ketamine has the deepest research base of any route, with multiple trials demonstrating rapid antidepressant response. Dosing precision and in-clinic monitoring are key advantages. The route requires in-person visits, physical infrastructure, and is typically the highest-cost option per session, and its most-studied status does not automatically translate to better long-term outcomes.

Intramuscular Ketamine Injections

Intramuscular ketamine is injected into a large muscle, usually the deltoid or gluteal. Providers typically administer it in a dedicated care setting. Bioavailability is approximately 93%.

Onset is slightly slower than intravenous delivery, usually beginning within a few minutes. Intramuscular delivery does not require IV access, which simplifies administration, but it still requires a physical visit and monitoring. It is less commonly studied than intravenous ketamine for mental health applications, and fewer clinics offer it as a primary modality.

Intranasal Esketamine (Spravato)

Spravato is an FDA-approved nasal spray containing esketamine. The FDA approved it specifically for treatment-resistant depression and major depressive disorder with suicidal ideation. It must be administered in a certified healthcare setting under a REMS program.

Patients self-administer the nasal spray under direct supervision, then remain for a minimum two-hour observation period. Bioavailability is approximately 48%. Because it is the only FDA-approved ketamine product for depression, it is more likely to be covered by insurance, though prior authorization and step-therapy requirements are common.

Spravato's FDA approval is a regulatory distinction, not an inherent efficacy advantage over racemic ketamine.

Sublingual Ketamine Tablets and Lozenges

Sublingual ketamine is absorbed through the oral mucosa by being held between the cheek and gum or under the tongue. Bioavailability ranges from approximately 25 to 35%, depending on formulation, hold time, and individual absorption.

Licensed physicians prescribe sublingual tablets and lozenges, which are dispensed by compounding pharmacies. They can be administered at home as part of a supervised program, removing the need for clinic visits. Onset is typically 10 to 15 minutes.

Session intensity can vary more than intravenous or subcutaneous routes due to differences in individual absorption. Of all at-home formats, sublingual ketamine is the most widely available.

Because absorption varies between individuals, defined protocols and provider oversight are especially important for sublingual delivery.

Subcutaneous Ketamine for At-Home Use

Subcutaneous ketamine is administered via a small insulin-gauge needle into the fatty tissue of the abdomen at home. Bioavailability is approximately 66%, higher than sublingual or intranasal routes.

Onset is approximately 5 minutes. Because the medication bypasses the digestive system and oral mucosa, absorption is more consistent and predictable than sublingual administration. Subcutaneous delivery is a newer at-home option and is not yet widely available across providers.

Subcutaneous racemic ketamine has been evaluated in a phase 3 randomized controlled trial for treatment-resistant depression. In the phase 3 trial, subcutaneous racemic ketamine showed antidepressant efficacy over 4 weeks and was tolerated within the response-guided study protocol.³

Subcutaneous ketamine offers higher bioavailability than sublingual or intranasal routes, providing more consistent session intensity without clinic visits. Mindbloom is the only at-home ketamine provider offering subcutaneous administration, which makes this higher-bioavailability at-home option available outside an infusion clinic.

*Daily low-dose oral protocols are not directly comparable to the routes above. Peer-reviewed response, remission, and durability data needed to evaluate them have not been published.

Which Type of Ketamine Therapy Is Most Effective?

There is no single best administration route, but the published evidence illuminates clear patterns when effectiveness is broken into measurable dimensions. The following sections walk through what the research shows on response rate, remission rate, and durability of benefit, the dimension that often matters most for sustained mental health outcomes. Daily low-dose oral protocols are addressed separately, since the published evidence needed to evaluate them comparatively does not yet exist.

What Effective Means: Response Rate, Remission, and Durability

Psychiatric research evaluates mental health treatments using specific standardized metrics.

• Response rate: The percentage of patients who experience a meaningful reduction in symptom severity, typically a 50% or greater reduction on a validated scale like the PHQ-9.
• Remission rate: The percentage of patients whose symptoms fall below the diagnostic threshold.
• Durability: How long symptom improvement is sustained after treatment, including whether benefits hold across multiple treatment rounds or decay after cessation.

A treatment can produce a high initial response rate but poor durability, meaning symptoms return quickly after stopping. For someone navigating a chronic mental health condition, durability is often the dimension that matters most. A treatment that works for two weeks and then decays is functionally different from a treatment whose benefits hold across multiple rounds.

The three dimensions don't carry equal weight in real-world treatment decisions, and the comparative evidence shows where the routes diverge most sharply on durability.

Response and Remission Rates by Administration Route

Published studies show that intravenous, sublingual, subcutaneous, and intranasal ketamine each produce measurable response and remission outcomes. Cross-study comparisons should be read with structural differences in mind, including TRD populations versus moderate-severe depression cohorts, controlled trials versus real-world cohorts, and in-clinic versus at-home settings, rather than as direct head-to-head comparisons.

Intravenous ketamine is the most-studied route, with multiple trials reporting rapid response within hours of a single infusion. Published benchmark studies and meta-analyses show single-infusion response rates of approximately 27% to 41% at 24 hours, with remission rates around 5% to 19%. Higher response rates of 50% to 60% are typically reported only after a series of repeated infusions.⁴^,⁹ These figures are measured at peak effect, within 24 hours of infusion, and the durability section below shows what happens to them in the weeks that follow. Most-studied is not the same as most effective. The volume of IV research reflects historical priority and clinical-trial accessibility, not necessarily superior outcomes versus other routes.

For at-home sublingual ketamine, the largest real-world study of any ketamine intervention published to date, an analysis of 11,441 patients with moderate-to-severe depression (baseline PHQ-9 = 15.5), evaluated outcomes within a managed at-home protocol.⁵ Response rates grew across the 4-week course. At Week 2, response was 42.3% and remission was 18.1% (Cohen's d = 1.15).⁵ By Week 4, response had climbed to 56.4% and remission to 28.1% (Cohen's d = 1.46, conventionally considered large), with 61.4% of patients achieving clinically significant change.⁵ The Cohen's d of 1.46 in this real-world cohort matches or exceeds the pooled effect sizes reported in published meta-analyses of IV ketamine trials, which is unusual for real-world data, since real-world effect sizes typically fall below those observed in controlled laboratory settings.^5,8,9 The trajectory direction, building across a structured multi-week course, contrasts with the rapid post-dose decline of a single IV infusion and the high post-cessation relapse rates reported after IV induction series.

For subcutaneous ketamine, a trial by Loo et al. evaluated a flexible-dose cohort over 4 weeks. Ketamine produced remission in 19.6% of patients and a meaningful symptom reduction in 29%.³ The trial enrolled treatment-resistant depression patients, which differs from the moderate-to-severe real-world cohort in the Mathai study.

For Spravato, the TRANSFORM-2 and SUSTAIN-1 registration trials demonstrated efficacy that led to its FDA approval. They showed significant symptom reduction compared to placebo plus an oral antidepressant.

At-home sublingual ketamine results, when delivered within a managed care protocol, are competitive with published intravenous ketamine benchmarks.⁸ The assumption that higher bioavailability automatically produces better outcomes is not supported by the comparative data.

How Durable Are the Outcomes? Comparing Across Routes

Durability measures how long symptom improvements last after an induction series and what happens when treatment stops.

Sustaining relief is a critical differentiator. Research by Smith-Apeldoorn et al. found that single-dose intravenous antidepressant benefits are virtually undetectable by two weeks, with high relapse rates within the first month of cessation even after repeated induction.⁶ Other studies confirm high relapse rates for intravenous ketamine shortly after treatment ends, and trials of other administration routes show similar attenuation when treatment is halted at the end of a brief induction.³,⁴,⁷

Across the published evidence, a clear pattern emerges: brief induction without ongoing structured care does not produce durable benefit, regardless of administration route. The durability differentiator is not the route. It is whether the protocol includes a defined maintenance pathway and integration support.

In contrast, the sublingual Mathai et al. study found that 84% of patients who achieved clinically significant change in Round 1 and elected a second four-week round either maintained or recovered that improvement.⁵ The 1,241-patient Round 2 cohort that produced this finding has no equivalent in the published IV ketamine literature, where the largest reported maintenance dataset tracked 23 responders. Managed multi-session protocols with integration support may contribute to more durable results than isolated infusion series without integration.

The durability evidence challenges the assumption that intravenous ketamine's higher bioavailability translates to longer-lasting benefit. At-home protocols with built-in integration show strong maintenance of improvement across treatment rounds.

Why Bioavailability Doesn't Equal Effectiveness

Higher bioavailability does not automatically translate to better outcomes, despite how frequently ketamine types are ranked by absorption alone.

Bioavailability describes how much of the drug reaches the bloodstream. It does not account for treatment frequency, protocol design, integration practices, therapeutic context, or patient adherence. A route with 100% bioavailability delivered without screening, integration, or follow-up may produce worse real-world outcomes than a lower-bioavailability route embedded in a comprehensive care program.

The Mathai et al. data demonstrates that sublingual ketamine within a comprehensive protocol produces effect sizes that are meaningful regardless of bioavailability ranking.⁵

As a single pharmacological variable, bioavailability cannot serve as a proxy for therapeutic effectiveness. Protocol design, ongoing monitoring, and integration are at least as important to results.

Where the Evidence Is Limited: Daily Low-Dose Ketamine

Daily or near-daily oral ketamine at very low doses, sometimes marketed as microdosing, currently lacks comprehensive peer-reviewed efficacy data for mental health conditions sufficient to support comparison with established protocols.

Peer-reviewed response, remission, and durability data across well-powered studies are not yet available for daily low-dose ketamine protocols in depression, anxiety, or PTSD at the scale needed to evaluate it alongside routes with established evidence bases. Without this published data, the effectiveness of this approach cannot be quantified or compared to other routes.

The lack of comprehensive data does not mean daily low-dose ketamine is ineffective. Rather, the evidence needed to evaluate it comparably does not yet exist in the published literature.

When evaluating the most effective options, readers should weigh whether a given approach has published outcomes data from independently reviewed studies. Protocols without this evidence base require a different standard of evaluation and informed consent.

Conclusion

Published evidence shows that ketamine outcomes vary by administration route, protocol design, and follow-up structure rather than by route alone. Intravenous ketamine is the most studied, but published evidence shows that at-home protocols produce competitive response, remission, and durability outcomes. Bioavailability alone does not predict therapeutic results. Daily low-dose approaches lack the peer-reviewed comparative efficacy data needed to evaluate them alongside established protocols. Until that evidence is published, their effectiveness should be considered unproven, not just unmeasured.

Evidence across routes suggests outcomes are stronger when ketamine is delivered within a managed care protocol that includes screening, continuous monitoring, and integration, with care personalized to the individual's needs and goals. Published outcomes data, detailed above, demonstrate what protocol-driven at-home ketamine treatment achieves at scale.

Readers considering ketamine treatment should evaluate providers based on published outcomes, care structure, and the comprehensiveness of the care model, not delivery method alone.

Important Safety Information

Ketamine is not FDA-approved for PTSD, depression, or anxiety. Common side effects include dissociation, increased blood pressure, nausea, dizziness, and cognitive impairment. Ketamine has abuse potential and is not appropriate for patients with uncontrolled hypertension, psychotic disorders, or substance use disorders. Do not drive or operate machinery until the day after treatment. Individual results may vary. Full safety information: www.mindbloom.com/safety-information

Off-Label Use Disclosure

Ketamine is FDA-approved only as an anesthetic. Use for mental health conditions represents off-label prescribing by licensed clinicians based on clinical judgment. Schedule III Controlled Substance - DEA regulations apply.