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Antidepressant Effects of Nitrous Oxide
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.
Study details:
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 \[VAS\]).
Eligibility criteria
Researchers look for people who fit a certain description, called eligibility criteria. See if you qualify.
Inclusion criteria
Exclusion criteria
Eligibility
Age eligible for study : 18 and older
Healthy volunteers accepted : Yes
Gender eligible for study: All
Things to know
Study dates
Study start: 2021-06-30
Primary completion: 2025-06-01
Study completion finish: 2025-08-01
Study type
TREATMENT
Phase
PHASE2
Trial ID
NCT05357040
Intervention or treatment
DRUG: Nitrous oxide gas for inhalation
DRUG: Placebo
Conditions
- • Major Depressive Disorder
- • Treatment Resistant Depression
Find a site
Closest Location:
The Alfred Hospital
Research sites nearby
Select from list below to view details:
The Alfred Hospital
Melbourne, Victoria, Australia
Study Plan
This section provides details of the study plan, including how the study is designed and what the study is measuring.
How is the study designed?
| Participant Group/Arm | Intervention/Treatment |
|---|---|
ACTIVE_COMPARATOR: Treatment; Nitrous Oxide 50% or 25%, group
| DRUG: Nitrous oxide gas for inhalation
|
PLACEBO_COMPARATOR: Control; Oxygen-air mixture, group
| DRUG: Placebo
|
What is the study measuring?
Primary outcome
| Primary Outcome Measure | Primary Outcome Description | Primary Outcome Time Frame |
|---|---|---|
| Change in HDRS-21 score | Monitor 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 | Over 4-weeks from baseline |
Secondary outcome
| Secondary Outcome Measure | Secondary Outcome Description | Secondary Outcome Time Frame |
|---|---|---|
| Treatment response | Treatment response (≥50% reduction on HDRS-21) to nitrous oxide vs placebo will be measured. | At 24-hours (following treatment-1) |
| Changes in 'Profile of Mood States' scores | 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 | Up to 1-week (following treatment-1) |
| Sustainability of treatment response | 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 | Over 7-weeks (length of study participation). |
| Treatment dose response comparison | 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. | Over 7-weeks (length of study participation) |
| Treatment cycle compliance | 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). | Over 4-weeks (weekly treatment sessions) |
| Changes in Computerize Adaptive Testing - Mental Health (CAT-MH) 'depression' scores | This 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 | Over 7-weeks (length of study participation) from Baseline |
| Changes in Computerize Adaptive Testing - Mental Health (CAT-MH) 'anxiety' scores | This 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 | Over 7-weeks (length of study participation) from Baseline |
| Changes in Computerize Adaptive Testing - Mental Health (CAT-MH) 'suicide' scores | This 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 | Over 7-weeks (length of study participation) from Baseline |
| Suicidal ideation tracking | Suicidal 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. | Over 7-weeks (length of study participation) from Baseline |
| Visual Analog Scale (VAS) | 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). | At Baseline (Prior to treatment-1) |
| Treatment remission | Treatment remission (HDRS-21 ≤7 points) to nitrous oxide vs. placebo will be measured. | At 24-hours (following treatment-1) |
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