Ketamine vs Esketamine in TRD: Clinical, Policy, and Access Implications

Ketamine and Esketamine: Two Approaches to Treatment-Resistant Depression

Ketamine and esketamine are distinct but related interventions for treatment-resistant depression (TRD), with ketamine widely used off-label and esketamine (marketed as Spravato) approved by the U.S. Food and Drug Administration (FDA) since 2019 for adults with TRD. Both act as N-methyl-D-aspartate (NMDA) receptor antagonists and are administered via different routes: intravenous (IV) or intramuscular (IM) for ketamine, and intranasal for esketamine. Esketamine is the S-enantiomer of racemic ketamine and was developed to offer a more standardized, regulated option for depression unresponsive to standard therapies.

The distinction between these two compounds is not only chemical but regulatory. While esketamine is on-label for TRD, ketamine use in psychiatry remains off-label, though it is supported by a growing body of clinical experience. This regulatory nuance shapes clinical practice, reimbursement, and patient access, as insurers are more likely to cover FDA-approved esketamine than generic ketamine, which is not specifically indicated for depression.

Mechanisms of Action and Clinical Evidence

Both ketamine and esketamine exert rapid antidepressant effects believed to involve NMDA receptor antagonism, downstream glutamatergic modulation, and increased synaptogenesis. Randomized controlled trials (RCTs) have demonstrated significant reductions in depressive symptoms within hours to days, a marked contrast to traditional antidepressants that may take weeks to show benefit. Esketamine's pivotal trials (e.g., TRANSFORM-2, NCT02418585) supported its approval for TRD, while ketamine's robust evidence base comes from both RCTs and real-world studies, though without formal FDA indication for depression.

Direct head-to-head comparisons between ketamine and esketamine are limited. Available evidence suggests similar efficacy in acute symptom reduction, but differences in duration of effect, tolerability, and patient experience remain under investigation. Notably, ketamine clinics often individualize dosing and offer flexible administration routes, while esketamine's use is tightly regulated under a Risk Evaluation and Mitigation Strategy (REMS) program, requiring administration in certified healthcare settings and post-dose monitoring.

Policy, Reimbursement, and Access Considerations

Coverage and reimbursement for ketamine and esketamine in TRD are shaped by their regulatory status and payer policies. Esketamine, as an FDA-approved product for TRD, is more likely to be reimbursed by commercial insurers and Medicare, though prior authorization and step therapy requirements are common. Ketamine, being generic and off-label, is often not covered, resulting in significant out-of-pocket costs for patients and limiting access to those who can afford private clinics.

This dynamic creates a two-tiered system: patients with robust insurance may access esketamine, while others may seek ketamine at their own expense. Some clinics have reported that patients who fail to respond to esketamine may subsequently benefit from ketamine, suggesting non-interchangeability in some cases. However, the lack of standardized protocols and long-term outcome data for both compounds complicates guideline development and payer decision-making. A non-obvious implication is that the regulatory and reimbursement environment may drive not only access, but also the evolution of clinical protocols and the structure of care delivery in this space.

Risks, Unknowns, and Real-World Challenges

Both ketamine and esketamine carry risks of dissociation, blood pressure elevation, and potential for misuse or dependence, though the risk profile differs between compounds and routes of administration. Esketamine's REMS program is designed to mitigate diversion and monitor acute adverse effects, while ketamine clinics vary widely in their safety protocols and patient selection criteria. Long-term safety data for repeated use of either compound remain limited, with concerns about cognitive effects, urinary tract symptoms, and potential for substance use disorder still under active investigation.

Another real-world challenge is the heterogeneity of patient response. Not all patients with TRD benefit from either intervention, and predictors of response are not yet well-defined. The absence of direct comparative trials leaves clinicians without clear evidence to guide selection between ketamine and esketamine, reinforcing the need for shared decision-making and close monitoring.

Looking Ahead: Research, Guidelines, and Evolving Practice

Future research will likely focus on head-to-head comparisons, long-term safety, and optimizing protocols for both ketamine and esketamine in TRD. Ongoing real-world evidence studies, such as those registered on ClinicalTrials.gov, will inform clinical guidelines and may influence payer policies. The evolving landscape will require collaboration among researchers, clinicians, payers, and regulators to balance efficacy, safety, and equitable access.

A key decision criterion that is often overlooked is the infrastructure and staffing required for safe administration: esketamine's REMS-mandated monitoring may be unfeasible in resource-limited settings, while ketamine's flexibility may be offset by inconsistent safety practices. As the field matures, harmonizing standards and addressing disparities in access will be critical for realizing the potential of these therapies in TRD.

Byline: Dr. Alex Chen, MD, MSc. Reviewed by Dr. Priya Rao, MD, October 2026. Research based on FDA, ClinicalTrials.gov, and manufacturer data; primary sources linked above.