A combination of dextromethorphan and bupropion, sold under the brand name Auvelity, has emerged as one of the most talked-about antidepressant pairings in recent years, earning FDA approval in August 2022 as a rapid-acting oral treatment for major depressive disorder. In its pivotal Phase 3 trial, 39.5 percent of patients achieved remission on Auvelity compared to just 17.3 percent on placebo — a striking gap that caught the attention of clinicians who had grown accustomed to modest incremental gains in depression pharmacology. But Auvelity is only one piece of a much larger shift in how researchers are approaching the roughly one-third of adults with major depression who do not respond to standard antidepressants alone. That shift matters enormously for dementia caregivers and brain health advocates.
Depression is both a risk factor for cognitive decline and a frequent companion to dementia itself, and treatment-resistant depression in older adults can accelerate functional deterioration in ways that ripple through entire families. When conventional medications fail — and after a third oral antidepressant, approximately 86 percent of patients still do not achieve remission — the consequences are not abstract. They show up as withdrawn parents, isolated spouses, and caregivers who are themselves falling apart. This article examines the antidepressant combinations and novel agents now showing genuine promise for treatment-resistant cases, from the newly approved esketamine nasal spray to psilocybin-assisted therapy in late-stage clinical trials. We will look at what the data actually shows, where the limitations are, and what a growing pipeline of over 50 clinical trials for treatment-resistant depression could mean for patients and families navigating this difficult terrain.
Table of Contents
- What Makes an Antidepressant Combination Effective for Treatment-Resistant Depression?
- Esketamine Monotherapy — A Breakthrough With Important Caveats
- Psilocybin-Assisted Therapy Enters Phase 3 — What the Trials Actually Show
- How Do These Options Compare for Patients Who Have Failed Multiple Treatments?
- The Investigational Pipeline and Why Glutamate Keeps Coming Up
- What Treatment-Resistant Depression Means for Brain Health and Dementia Risk
- Where the Field Is Heading and What Families Should Watch For
- Conclusion
- Frequently Asked Questions
What Makes an Antidepressant Combination Effective for Treatment-Resistant Depression?
The traditional approach to depression that does not respond to a first medication has been to switch drugs or add a second one — a strategy called augmentation. For decades, clinicians have paired SSRIs with atypical antipsychotics like aripiprazole, or combined antidepressants that work through different mechanisms, hoping to cover more neurochemical ground. The problem is that these strategies were often based on clinical intuition and small trials rather than robust evidence, and the remission rates remained stubbornly low. What distinguishes the newer combinations is a deliberate focus on biological pathways beyond serotonin and norepinephrine, particularly the glutamate system, which plays a central role in synaptic plasticity and neural communication. Auvelity illustrates this principle well. Dextromethorphan acts on NMDA glutamate receptors, sigma-1 receptors, and serotonin transporters, while bupropion serves a dual purpose: it has its own antidepressant properties through norepinephrine and dopamine reuptake inhibition, and it also inhibits the enzyme that would otherwise break down dextromethorphan too quickly in the body. The ASCEND Phase 2 trial, which enrolled 97 adults, demonstrated that this pairing produced MADRS score reductions of 14 points compared to 9 points for bupropion alone, with remission rates of 47 percent versus 16 percent.
That is not a subtle difference. A network meta-analysis of treatments for resistant depression identified six approaches with response rates significantly higher than placebo: electroconvulsive therapy, minocycline, theta-burst stimulation, repetitive transcranial magnetic stimulation, ketamine, and aripiprazole augmentation. The newer drug combinations are attempting to match or exceed those benchmarks with better tolerability. However, the distinction between major depressive disorder and treatment-resistant depression matters critically here. Auvelity’s strongest data comes from the GEMINI trial, which enrolled 327 adults with MDD broadly — not specifically patients who had already failed multiple medications. A separate trial conducted solely in treatment-resistant depression patients failed to detect a difference between Auvelity and placebo after six weeks. That is a significant caveat. A drug that works well in general depression populations may not translate directly to the hardest-to-treat cases, and anyone evaluating these combinations should ask exactly which population was studied.
Esketamine Monotherapy — A Breakthrough With Important Caveats
Esketamine, marketed as Spravato, has arguably done more than any other recent treatment to change the conversation about treatment-resistant depression. Originally approved in 2019 as an add-on to an oral antidepressant for TRD patients, esketamine took a major step forward in February 2025 when the FDA approved it as the first and only monotherapy for adults with treatment-resistant depression who had inadequate response to at least two oral antidepressants. This means patients can now use the nasal spray without being required to take a conventional antidepressant alongside it — a meaningful change for people who have experienced intolerable side effects from multiple oral medications. The pivotal monotherapy trial, known as Study 3, randomized 378 adults to receive either 56 mg or 84 mg doses of esketamine twice weekly, and both doses showed statistically significant improvement over placebo by day 28. Esketamine monotherapy achieved remission in 15 percent more patients than placebo at 28 days, and some patients demonstrated measurable improvement in depressive symptoms as early as 24 hours after their first intranasal dose. That speed is remarkable.
Most oral antidepressants require four to six weeks before their effects become apparent, and for someone in acute crisis — particularly an older adult whose depression is compounding cognitive decline — those weeks can feel like an eternity. The limitations are real, though. Esketamine must be administered in a certified healthcare setting under medical supervision, with patients monitored for at least two hours afterward due to risks of dissociation, sedation, and blood pressure changes. For a caregiver already stretched thin, arranging twice-weekly clinical visits is not trivial. The drug also carries a boxed warning about the potential for abuse and misuse. And while the rapid onset is genuinely impressive, the long-term data on sustained remission with esketamine monotherapy is still accumulating. Clinicians working with older adults and dementia patients should weigh these logistical and safety considerations carefully, especially given that dissociative side effects may be more disorienting in populations already experiencing cognitive challenges.
Psilocybin-Assisted Therapy Enters Phase 3 — What the Trials Actually Show
Perhaps the most unexpected entrant in the treatment-resistant depression field is COMP360 psilocybin, developed by Compass Pathways, which became the first classic psychedelic to complete not one but two Phase 3 clinical trials. The COMP005 trial, reported in June 2025, enrolled 258 participants across 32 U.S. sites and found that a single 25 mg dose of psilocybin produced a mean treatment difference of negative 3.6 points on the MADRS scale compared to placebo, a result that was statistically significant at p less than 0.001. The COMP006 trial, reported in February 2026, tested two fixed 25 mg doses administered three weeks apart and showed a negative 3.8 point difference versus a 1 mg control dose. What makes these results particularly noteworthy is not just the magnitude of the effect but its duration. In responders, the benefits from just one or two doses lasted at least 26 weeks — half a year of sustained improvement from a treatment that takes a single day to administer. Among participants receiving the 25 mg dose, 39 percent achieved a clinically meaningful reduction of at least 25 percent on the MADRS at week six.
Adverse events were mostly mild to moderate and resolved within 24 hours. For a patient population that has, by definition, failed to respond to conventional treatments, those numbers represent something genuinely different from yet another pill to take every morning. Compass Pathways plans to submit a new Drug Application to the FDA in the fourth quarter of 2026. But even if approved, psilocybin therapy would face enormous practical hurdles. The treatment requires trained therapists, controlled clinical settings, and hours of supervised sessions. Access will almost certainly be limited initially to specialized centers, and cost and insurance coverage remain open questions. For older adults, especially those with any degree of cognitive impairment, the psychological intensity of a psilocybin experience raises additional considerations that have not been thoroughly studied. The trials enrolled adults with treatment-resistant depression broadly, not specifically elderly or dementia-adjacent populations.
How Do These Options Compare for Patients Who Have Failed Multiple Treatments?
Choosing among these emerging options is not straightforward, because each one comes with a distinct set of tradeoffs around efficacy, convenience, speed of onset, and practical accessibility. Auvelity offers the simplicity of an oral medication taken twice daily at home — no clinic visits, no supervision — but its strongest evidence is in general major depression rather than confirmed treatment-resistant cases. Esketamine has the most robust TRD-specific data and FDA approval as monotherapy for that population, but it requires biweekly clinic visits with two-hour monitoring periods. Psilocybin, if approved, would demand the least frequent dosing of all — one or two sessions potentially providing months of benefit — but the infrastructure for delivering it does not yet exist at scale. For caregivers and families navigating dementia alongside depression, these practical considerations matter as much as the clinical trial numbers. An 80-year-old with moderate Alzheimer’s disease and treatment-resistant depression is a very different patient from the typical clinical trial participant, who tends to be younger and without significant cognitive comorbidities.
The dissociative effects of esketamine, the psychological intensity of psilocybin, and the limited TRD data for Auvelity all represent real concerns in this population. There is also the broader question of whether a treatment that improves mood scores on a rating scale translates into functional improvements that matter in daily life — the ability to engage with family, participate in activities, or tolerate the demands of a care setting. Those outcomes are rarely primary endpoints in the trials. The six treatments identified in network meta-analysis research as having higher response rates than placebo — ECT, minocycline, theta-burst stimulation, rTMS, ketamine, and aripiprazole augmentation — remain important parts of the conversation. ECT, despite its stigma, continues to show the largest effect sizes for severe, treatment-resistant depression and has decades of data in older adults. For some patients, the established options may still be the most appropriate choice, even as newer agents attract more attention.
The Investigational Pipeline and Why Glutamate Keeps Coming Up
Beyond the treatments already approved or in late-stage trials, a substantial investigational pipeline is taking shape. A recent review identified 50 clinical trials focused on treatment-resistant depression, 20 on anhedonia — the inability to feel pleasure, which is one of depression’s most disabling symptoms — and 25 on suicide prevention. The common thread running through much of this research is the glutamate system, which is the mechanism with the most compounds currently in development. This is a direct legacy of the ketamine revolution: the discovery that a drug acting on NMDA receptors could lift severe depression within hours fundamentally redirected the field’s attention away from the serotonin hypothesis that had dominated for decades. One investigational combination that illustrates this direction is NRX-101, which pairs high-dose D-cycloserine at 950 mg per day with the atypical antipsychotic lurasidone. This combination is being tested specifically for anti-suicidal effects in bipolar-depressed patients, a population where treatment options are particularly limited and the stakes are highest.
The related formulation NRX-100, a single-dose ketamine product for suicidal depression, has received FDA Fast Track designation, with regulatory decisions expected by mid-2026. A word of caution about the pipeline is warranted. The history of psychiatry is littered with treatments that showed promise in early trials and failed in larger, more rigorous ones. The drop-off from Phase 2 to Phase 3 success is steep, and even treatments that clear the regulatory bar may prove difficult to implement in real-world clinical settings. For families dealing with treatment-resistant depression in the context of dementia care, it is worth following these developments without pinning too much hope on any single compound. The most reliable strategy remains working with a psychiatrist who stays current on the evidence and is willing to try multiple approaches systematically.
What Treatment-Resistant Depression Means for Brain Health and Dementia Risk
The overlap between treatment-resistant depression and dementia is more than incidental. Chronic, poorly controlled depression is associated with hippocampal volume loss, elevated cortisol, neuroinflammation, and disruptions to brain-derived neurotrophic factor — all mechanisms that are also implicated in Alzheimer’s disease and other dementias. When depression resists treatment for months or years, these processes continue unchecked, potentially accelerating cognitive decline in vulnerable individuals.
Some researchers have argued that treatment-resistant depression in late life should itself be considered a prodromal neurodegenerative condition in certain cases. This is why the emergence of faster-acting, more effective treatments for resistant depression has implications beyond mood. If esketamine can achieve remission within days rather than months, or if psilocybin can sustain improvement for half a year from a single dose, the cumulative neurobiological burden of untreated depression may be substantially reduced. Whether that translates into measurable protection against dementia remains an open question — the studies have not been designed to answer it — but the biological rationale is sound, and it gives the current wave of treatment innovation an urgency that extends well beyond psychiatry.
Where the Field Is Heading and What Families Should Watch For
The next two to three years will be pivotal. Compass Pathways’ anticipated NDA submission in late 2026 could bring the first psychedelic-assisted therapy to market. Regulatory decisions on NRX-100 for suicidal depression are expected by mid-2026. And the broader pipeline of glutamate-targeting compounds, neuromodulation approaches, and combination strategies will continue generating data that reshapes how clinicians think about depression that does not respond to first-line treatment.
For families navigating dementia care, the practical advice is to stay informed without chasing every headline. Ask your loved one’s psychiatrist specifically about treatment-resistant depression options, including esketamine if clinic-based treatment is feasible. Keep in mind that the estimated 21 million adults in the U.S. living with major depressive disorder includes a substantial number of older adults in caregiving or care-receiving situations, and the one-third who do not respond to standard treatment deserve more than therapeutic nihilism. The science is finally catching up to the scale of the problem.
Conclusion
The landscape for treatment-resistant depression is changing faster than it has in decades. Auvelity brought a novel oral combination to market with impressive general-depression data, though its performance in confirmed TRD patients remains less clear. Esketamine’s expansion to standalone monotherapy in February 2025 gave treatment-resistant patients a validated option that works within hours. And psilocybin’s successful Phase 3 results have moved a once-fringe concept to the doorstep of regulatory approval.
Behind these headline treatments, a pipeline of over 50 clinical trials is exploring everything from glutamate modulators to novel neuromodulation techniques. None of these treatments is a silver bullet, and all of them carry limitations that matter — particularly for older adults and individuals with cognitive impairment. But the collective direction is unmistakable: psychiatry is moving beyond the strategy of cycling through similar medications and hoping for different results. For families affected by treatment-resistant depression, especially those also managing dementia, these developments offer a reason for cautious, evidence-based hope. The most important step remains finding a clinician who is aware of these options and willing to pursue them systematically.
Frequently Asked Questions
What qualifies as treatment-resistant depression?
Treatment-resistant depression is generally defined as major depressive disorder that has not adequately responded to at least two different antidepressant medications taken at adequate doses for adequate durations. After trying a third oral antidepressant, approximately 86 percent of patients still do not achieve remission, which underscores how common and difficult this problem is.
Is Auvelity specifically approved for treatment-resistant depression?
No. Auvelity (dextromethorphan/bupropion) is FDA-approved for major depressive disorder broadly, not specifically for treatment-resistant cases. Its main clinical trials excluded TRD patients, and a trial conducted solely in treatment-resistant patients failed to show a difference from placebo. It may still be prescribed off-label for TRD, but the evidence base for that specific use is limited.
How quickly does esketamine (Spravato) work compared to traditional antidepressants?
Esketamine demonstrated improvement in depressive symptoms as early as 24 hours after the first intranasal dose, with significant improvements over placebo by day 28 in clinical trials. Traditional oral antidepressants typically require four to six weeks before their full effects become apparent.
Is psilocybin therapy currently available for treatment-resistant depression?
Not yet through standard medical channels. COMP360 psilocybin has completed two successful Phase 3 clinical trials, and Compass Pathways plans to submit a New Drug Application to the FDA in the fourth quarter of 2026. If approved, it would likely be available only at specialized treatment centers initially.
Are these new treatments safe for older adults or people with dementia?
The clinical trials for these treatments primarily enrolled younger to middle-aged adults without significant cognitive comorbidities. Safety and efficacy in older adults, particularly those with dementia, have not been specifically established. Esketamine’s dissociative effects and psilocybin’s psychological intensity may pose additional concerns for cognitively impaired individuals. Any use in these populations should involve careful discussion with a psychiatrist experienced in geriatric care.
What other treatments have evidence for treatment-resistant depression?
A network meta-analysis identified six treatments with response rates significantly higher than placebo: electroconvulsive therapy, minocycline, theta-burst stimulation, repetitive transcranial magnetic stimulation, ketamine, and aripiprazole augmentation. ECT continues to show the largest effect sizes and has the longest track record in older adults.
