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Antidepressant Effects of Nitrous Oxide

Evaluation of the Antidepressant Effects of Nitrous Oxide in People With Major Depressive Disorder

Status
Withdrawn
Phases
Phase 2
Study type
Interventional
Source
ClinicalTrials.gov
Registry ID
NCT05357040
Enrollment
0
Registered
2022-05-02
Start date
2021-06-30
Completion date
2026-02-27
Last updated
2026-05-14

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Major Depressive Disorder, Treatment Resistant Depression

Keywords

Depression, Antidepressant, Nitrous Oxide

Brief summary

To evaluate the acute and sustained antidepressant effects of nitrous oxide in people with major depressive disorder; and further evaluate these effects by identifying the optimal dose and regimen to guide current practice, and to plan a future large pragmatic trial.

Detailed description

The investigators are conducting a randomized controlled trial to evaluate the antidepressant effects of nitrous oxide in people with Major Depressive Disorder (MDD). MDD is a global medical condition that causes significant health and economic burden. Recent studies have shown that a single dose of ketamine, an NMDA-antagonist, has fast and long lasting anti-depressant effect. Nitrous oxide, another NMDA-antagonist, is widely used for anesthesia and analgesia, safer to administer and has fewer side effects than ketamine. A randomized controlled crossover feasibility study showed significant reduction in depressive symptoms at 2 and 24 hours after a single 1-hour treatment session of inhaled nitrous oxide compared with placebo. Nitrous oxide is inexpensive and can be safely administered by any trained clinician. If found to be efficacious, it could be used to provide rapid anti-depressant effect whilst the benefit of traditional anti-depressants has its delayed effect. Another potential application could be in acutely suicidal patients. This trial will enable confirmation and extension of the findings from the feasibility study, and identify the optimal dose and regimen in a broader population of those with MDD. Participants will be randomized to receive a weekly 1-hour inhalational session of either nitrous oxide or placebo (oxygen-air mixture) for 4 weeks, and the nitrous group will be further randomly assigned to a dose of 50% or 25% nitrous oxide. Depression severity and outcomes related to treatment responses will be continuously assessed by a 'blinded-to-randomization' psychiatry (MD) rater at weekly intervals during study patient participation, using validated psychiatric diagnostics (Hamilton Depression Rating Scale-21 \[HDRS-21 or HAM-D\]; Profile of Mood States \[POMS\]; Computerized Adaptive Test-Mental Health \[CAT-MH\]; Sheehan-STS \[S-STS\]; Visual Analog Scale \[VAS\]).

Interventions

60-minute sessions of inhaled 50% nitrous oxide in oxygen (FiO2 0.5) or 25% nitrous oxide in oxygen (FiO2 0.75), administered weekly for 4-weeks. Administration will be under the direct supervision of a licensed practitioner who is experienced in the use and administration of the study drug, and is familiar with the indications, effects, dosages, methods, and frequency and duration of administration, and with the hazards, contraindications, and side effects and the precautions to be taken (MD, or CRNA); with study patient monitoring of pulse oximetry, heart rate, respiratory, non-invasive blood pressure, and end-tidal carbon dioxide.

DRUGPlacebo

60-minute sessions of inhaled oxygen-air mixture (FiO2 ≈0.3) to be administered weekly for 4-weeks. Administration will be under the direct supervision of a licensed practitioner who is experienced in the use and administration of the study drug, and is familiar with the indications, effects, dosages, methods, and frequency and duration of administration, and with the hazards, contraindications, and side effects and the precautions to be taken (MD, or CRNA); with study patient monitoring of pulse oximetry, heart rate, respiratory, non-invasive blood pressure, and end-tidal carbon dioxide.

Sponsors

University of Chicago
Lead SponsorOTHER
The Alfred
CollaboratorOTHER

Study design

Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
DOUBLE (Subject, Outcomes Assessor)

Masking description

Patient and assessor blinded to study group assigned.

Intervention model description

Parallel-group, controlled trial; randomized participants (1:1) to nitrous oxide (Nitrous group) or oxygen-air mixture (FiO2 ≈0.3, Control group). The Nitrous group will be further randomly assigned to either 50% nitrous oxide in oxygen (FiO2 0.5) or 25% nitrous oxide in oxygen (FiO2 0.75).

Eligibility

Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes

Inclusion criteria

1. Adult (≥18 years, both sexes) 2. DSM-5 criteria for MDD without psychosis, as determined using a structured clinical interview \[Mini International Neuropsychiatric Interview\], MDD, defined by a pre-treatment score \>16 on the HDRS-21 scale and meeting DSM-5 for MDD

Exclusion criteria

1. A current or past history of bipolar disorder, schizophrenia, or schizoaffective disorder. 2. Current obsessive-compulsive disorder, panic disorder, or documented Axis II diagnoses 3. Active suicidal intention, as determined by clinical interview assessment tool (Sheehan-STS) and clinical examination 4. Active or recent (\<12 months) substance use disorder; excluding nicotine 5. Administration of NMDA-antagonists (e.g., ketamine) in previous 3 months 6. Ongoing treatment with ECT 7. Presence of acute medical illness that could interfere with study participation, including significant pulmonary disease 8. Pregnancy or breastfeeding 9. Any contraindications to the use of nitrous oxide (e.g., pneumothorax, middle ear occlusion, elevated intracranial pressure, chronic cobalamin or folate deficiency unless treated with folic acid or vitamin B12).

Design outcomes

Primary

MeasureTime frameDescription
Change in HDRS-21 scoreOver 4-weeks from baselineMonitor changes in Hamilton Depression Rating Scale-21 (HDRS-21) scores to determine whether a series of four, 60-minute sessions of inhaled nitrous oxide vs placebo (once-per-week) has significant antidepressant activity. The HDRS-21 is an interview-based psychiatric diagnostic used to evaluate depression severity. Scores are calculated by using the first 17 responses of this 21 item questionnaire. Higher scores are associated with more severe depression: 0 - 7 = Normal 8 - 13 = Mild Depression 14-18 = Moderate Depression 19 - 22 = Severe Depression \> 23 = Very Severe Depression Max score = 52

Secondary

MeasureTime frameDescription
Treatment responseAt 24-hours (following treatment-1)Treatment response (≥50% reduction on HDRS-21) to nitrous oxide vs placebo will be measured.
Changes in 'Profile of Mood States' scoresUp to 1-week (following treatment-1)Monitoring daily mood changes using the Profile of Mood States (POMS) a validated 'self-report' psychological diagnostic containing 65 emotions or 'mood states' to determine the pattern of treatment response Patients rank their current mood states using a scale of 'not-at-all', 'a-little', 'moderately', 'quite-a-lot', 'extremely'. Responses are scored to calculated the Total Mood Disturbance (TMD): TMD = (tension + depression + anger + fatigue + confusion) - Vigor
Sustainability of treatment responseOver 7-weeks (length of study participation).Determine sustained response and remission following study treatments (nitrous vs placebo) using Hamilton Depression Rating Scale-21 (HDRS-21) score. The HDRS-21 is an interview-based psychiatric diagnostic used to evaluate depression severity. Scores are calculated by using the first 17 responses of this 21 item questionnaire. Higher scores are associated with more severe depression: 0 - 7 = Normal 8 - 13 = Mild Depression 14-18 = Moderate Depression 19 - 22 = Severe Depression \> 23 = Very Severe Depression Max score = 52
Treatment dose response comparisonOver 7-weeks (length of study participation)Compare dose response of 25% vs 50% nitrous oxide to establish whether the concentration is related to outcome. Determined with treatment-by-dose (group) interaction term in a logistic regression model to assess for statistical significance.
Treatment cycle complianceOver 4-weeks (weekly treatment sessions)Evaluate compliance to complete 4-cycle inhalation treatments of nitrous oxide vs placebo. Determined by ability, inability, or refusal to receive all 4-treatments of randomized inhalation sessions (nitrous oxide vs placebo).
Changes in Computerize Adaptive Testing - Mental Health (CAT-MH) 'depression' scoresOver 7-weeks (length of study participation) from BaselineThis CAT-MH is a validated self-reporting diagnostic that adaptively selects a small optimal set of items from a large bank of approximately 1,500 items, targeted to individuals current or historical level of severity and likelihood of 'depression'. Generated scores include severity and liklihood percentile: \- depression = (%) normal, mild, moderate, severe
Changes in Computerize Adaptive Testing - Mental Health (CAT-MH) 'anxiety' scoresOver 7-weeks (length of study participation) from BaselineThis CAT-MH is a validated self-reporting diagnostic that adaptively selects a small optimal set of items from a large bank of approximately 1,500 items, targeted to individuals current or historical level of severity and likelihood of 'anxiety'. Generated scores include severity and liklihood percentile: \- anxiety = (%) normal, mild, moderate, severe
Changes in Computerize Adaptive Testing - Mental Health (CAT-MH) 'suicide' scoresOver 7-weeks (length of study participation) from BaselineThis CAT-MH is a validated self-reporting diagnostic that adaptively selects a small optimal set of items from a large bank of approximately 1,500 items, targeted to individuals current or historical level of severity and likelihood of 'suicide'. Generated scores include severity and liklihood percentile: \- suicide = (%) low, intermediate, high
Suicidal ideation trackingOver 7-weeks (length of study participation) from BaselineSuicidal ideation will be be tracked using the Sheehan Suicidality Tracking Scale (S-STS), a validated self-report diagnostic tool designed to assess and monitor suicidality. The standard S-STS consists of 14 core questions related to suicidality phenomena and is designed for use in clinical research studies and in clinical settings. Scores are summed based on individual responses 'not-at-all = 0', 'a little = 1', 'moderately = 2', 'very = 3', 'extremely = 4', to generate a summated score (total score), individual factor scores for suicidal ideation, suicidal intent, suicidal planning, suicidal behavior, and non-suicidal self-injury. All results are monitored in real time by a trained psychiatry (MD) rater.
Visual Analog Scale (VAS)At Baseline (Prior to treatment-1)The VAS is a unidimensional measure of pain intensity and use in the field of psychology to measure 'well-being'. Patients mark on a line the point that they feel represents their perception of their current state, with the score determined by measuring in millimetres from the left hand end of the line to the point that the patient marks. The range of score from 0-100 mm and represent: no pain (0-4 mm), mild pain(5-44 mm), moderate pain (45-74 mm), and severe pain (75-100 mm).
Treatment remissionAt 24-hours (following treatment-1)Treatment remission (HDRS-21 ≤7 points) to nitrous oxide vs. placebo will be measured.

Countries

Australia, United States

Contacts

PRINCIPAL_INVESTIGATORPeter Nagele, MD, MSc

University of Chicago, Department of Anesthesia and Critical Care

PRINCIPAL_INVESTIGATORPaul Myles, MD

The Alfred Hospital, Department of Anesthesiology and Perioperative Medicine

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: May 15, 2026