A low-dose opioid was tested to make ketamine's anti-suicidal effect last longer

Intravenous ketamine can reduce suicidal thinking within hours — one of the few interventions in psychiatry that works that fast — but the effect typically fades within days [s1]. That short window is the problem clinicians keep running into: how to carry a patient through the dangerous period after the drug wears off. A small, NIH-funded trial from Stanford University tested an unusual idea for bridging that gap, giving patients a low dose of the opioid buprenorphine as a follow-on treatment, and reported that it kept the anti-suicidal benefit going [s1][s2].

The rationale is mechanistic. Laboratory and clinical work has suggested that ketamine's antidepressant and anti-suicidal actions may be partly mediated through the brain's mu-opioid receptor, and buprenorphine is a partial agonist at that receptor [s1]. The hypothesis was that a small, steady dose might extend what a single ketamine infusion starts.

The design

This was a randomised, double-blind, placebo-controlled trial at a single outpatient centre in the United States, registered as NCT04116528 [s1][s2]. Adults with major depressive disorder and a total score of at least 6 on the Scale for Suicide Ideation (SSI) were enrolled, and all first received a single open-label intravenous ketamine infusion of 0.5 mg/kg over 40 minutes [s1]. Beginning 48 hours later, participants were randomly assigned 1:1 to receive either sublingual buprenorphine, dosed flexibly from 0.2 to 0.8 mg per day, or a matching placebo, for four weeks [s1]. The primary outcome was the change in SSI total score, assessed weekly from day 1 through day 31 [s1].

Recruitment ran from November 2020 to March 2025 [s1]. Fifty participants, 68% of them female, received the ketamine infusion, and 45 completed at least one week of the follow-on treatment [s1].

What it found

Both groups improved after ketamine — as expected — but the buprenorphine group improved more [s1]. The mean reduction in SSI total score was −11.6 points (standard deviation 5.8) in the buprenorphine group of 23 patients, against −6.3 points (standard deviation 7) in the placebo group of 22 [s1]. The between-group effect was moderate to large, a Glass delta of 0.76 (95% confidence interval 0.11 to 1.39), and a mixed-effects model found a significant time-by-treatment interaction (p < 0.001), meaning the two groups diverged over the four weeks [s1]. Depression scores overall did not differ significantly between the groups, suggesting the benefit was specific to suicidal ideation rather than a broad lift in mood [s1]. No serious treatment-related adverse events were reported [s1].

The authors describe this as the first evidence that a drug can sustain and extend ketamine's anti-suicidal effect [s1]. That framing is deliberate: dozens of trials have shown ketamine's rapid but fleeting benefit, and the clinical gap has always been what to do next. A cheap, oral, widely available agent that could hold the line would, if it survived larger testing, be a meaningful addition to crisis care — which is precisely why the result needs scrutiny rather than enthusiasm [s1].

What this does and doesn't establish

The caution here is considerable, and it starts with size and setting. This was 50 participants at a single centre, with 45 contributing follow-on data — a sample small enough that a few patients can swing the result, which the wide confidence interval around the effect reflects [s1]. Everyone received open-label ketamine first, so the trial tests buprenorphine as an add-on, not ketamine itself [s1]. The follow-up ran only to day 31, leaving open whether the benefit lasts beyond a month or what happens when buprenorphine stops [s1].

There is also the nature of the drug. Buprenorphine is an opioid, used mainly to treat opioid use disorder and pain, and any proposal to give it to patients in a suicidal crisis carries obvious risks around dependence and overdose that a 50-person trial cannot characterise — the dose here was deliberately very low, but the safety question is exactly the kind that needs a far larger study to answer [s1]. The registry classifies the study as a phase 3 trial, but its scale is that of an early proof-of-concept [s2].

What to watch

Larger, multi-site replication with longer follow-up is the necessary next step, along with careful mapping of who benefits and at what risk [s1][s2]. Ketamine and esketamine are already used for treatment-resistant depression and acute suicidality in specialist settings; whether an opioid bridge becomes part of that toolkit depends entirely on evidence this trial is too small to provide. This article describes early-stage research and is not medical advice.

If you or someone you know is struggling with thoughts of suicide, help is available. In the US, call or text the 988 Suicide and Crisis Lifeline; in the UK and Ireland, call Samaritans on 116 123. Elsewhere, contact a local crisis line or emergency services.

Sources

• Low-Dose Buprenorphine Following Ketamine Treatment for Suicidal Ideation in Major Depressive Disorder — American Journal of Psychiatry, 19 May 2026
• Opiate Suicide Study in Patients With Major Depression (NCT04116528) — ClinicalTrials.gov