Nitrous Oxide for the Treatment of Major Depressive Disorder

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

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 investigated-initiated phase 2b 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 sessions 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% nitrous oxide or 25% nitrous oxide. Depression severity will be assessed by a blinded observer pre-treatment and at weekly intervals during and for 4 weeks after treatment using the Hamilton Depression Rating Scale.

Study Overview

• Status: Completed
• Conditions: Depression; Major Depressive Disorder
• Intervention / Treatment: Drug: Nitrous Oxide; Drug: Placebo

• Study Type: Interventional
• Enrollment (Actual): 81
• Phase: Phase 2

Contacts and Locations

Study Locations

• Australia
  • Victoria
    • Melbourne, Victoria, Australia, 3004
      • Alfred Hospital
• United States
  • Illinois
    • Chicago, Illinois, United States, 60637
      • University of Chicago Medicine

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Adult (≥18 years, both sexes), with DSM-IV-TR criteria for MDD without psychosis, as determined using a structured clinical interview [Mini International Neuropsychiatric Interview]
2. MDD, as defined by a pretreatment score >18 on the HDRS-21 scale

Exclusion Criteria:

1. A history of bipolar disorder, schizophrenia, schizoaffective disorder, obsessive-compulsive disorder, panic disorder, or documented Axis II diagnoses; active suicidal intention, as determined by clinical interview
2. Active or recent (<12 months) substance abuse or dependence; excluding nicotine
3. Administration of NMDA-antagonists (e.g., ketamine) in previous 3 months
4. Ongoing treatment with ECT
5. Presence of acute medical illness that could interfere with study participation, including significant pulmonary disease
6. Pregnancy or breastfeeding
7. 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).

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Nitrous Oxide 50% or 25%; Nitrous oxide at an inhaled concentration of 50% or 25%	Drug: Nitrous Oxide; 1-hour sessions of inhaled nitrous oxide at concentrations of 25% or 50% (randomly assigned) to be administered weekly for 4 weeks.
Sham Comparator: Placebo; Oxygen-air mixture	Drug: Placebo; 1-hour sessions of inhaled oxygen-air mixture (inspired oxygen concentration ~23-30%) to be administered weekly for 4 weeks.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in HDRS-21 score	21-point Hamilton Depression Rating Scale Interview-based questionnaire used to measure the severity of depression. Consists of 21 items with a score calculated from the first 17 answers. 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 Measures

Outcome Measure	Measure Description	Time Frame
Treatment response and remission	Treatment response (≥50% reduction on HDRS-21) and remission (HDRS-21 ≤7 points), nitrous oxide vs. placebo	at 24 hours
Pattern of treatment response	Assessed using daily Profile of Mood States scale. The POMS measures six different dimensions of mood swings over a period of time. score range with lower scores indicative of people with more stable mood profiles The Profile of Mood States (POMS) questionnaire is a validated psychological test containing 65 emotions/ mood states. Participants are asked to rank their current mood states using the scale 'not at all', 'a little', 'moderately', 'quite a lot' or 'extremely'. Total Mood Disturbance (TMD) score and an analysis of tension, depression, anger, vigour, fatigue and confusion is performed based on the participants mood states. Total Mood Disturbance (TMD) can be calculated by adding the scores for Tension, Depression, Anger, Fatigue and Confusion and then subtracting the score for Vigour. • TMD = (Tension + Depression + Anger + Fatigue + Confusion) - Vigour	Up to 1 week after treatment
Sustainability of treatment response - change in HDRS-21 scores	Change in the HDRS-21 score, nitrous oxide vs placebo HDRS-21 is an interview-based questionnaire used to measure the severity of depression. Consists of 21 items with a score calculated from the first 17 answers. 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
Sustainability of treatment response - response and remission rates	Response and remission rates (%), nitrous oxide vs placebo	over 7 weeks
Treatment compliance rate	Refusal or inability to attend further treatments, nitrous oxide vs placebo	over 4 weeks
Dose effect of nitrous oxide using treatment-by-dose interaction term in a logistic regression model	Dose effect of nitrous oxide at 25% and 50% using a treatment-by-dose (group) interaction term in a logistic regression model to assess for statistical significance.	over 7 weeks
Computerized Adaptive Test-Depression Inventory (CAT-DI)	Adaptive testing questionnaire that assesses severity, likelihood and percentile of depression based on an average of 12 items administered from a question bank of 400 items. Questions are adapted to the participants answers and targeted to their level of impairment. Results generate include: severity of depression (normal, mild, moderate, severe), likelihood of depression (out of probability of 1), percentile of severity.	over 7 weeks
Computerized Adaptive Test-Suicide Scale (CAT-SS)	Adaptive testing questionnaire that assesses risk and severity of suicide based on items administered from a question bank. Questions are adapted to the participants answers and targeted to their level of impairment. Results generate include: risk of suicide (low, intermediate, high) and a percentile of risk.	over 7 weeks

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Adverse events	Psychiatric AEs, such as new suicidal ideation and psychotic symptoms Other AEs, such as cardiorespiratory AEs or nausea and vomiting	over 7 weeks

Collaborators and Investigators

• Sponsor: Bayside Health
• Investigators: Principal Investigator: Paul Myles, MD, The Alfred

Study record dates

Study Major Dates

• Study Start (Actual): January 22, 2019
• Primary Completion (Actual): June 10, 2023
• Study Completion (Actual): December 10, 2023

Study Registration Dates

• First Submitted: December 16, 2018
• First Submitted That Met QC Criteria: March 7, 2019
• First Posted (Actual): March 11, 2019

Study Record Updates

• Last Update Posted (Actual): March 25, 2025
• Last Update Submitted That Met QC Criteria: December 10, 2024
• Last Verified: December 1, 2024

More Information

Terms related to this study

• Keywords: Depression; Mood Disorders; Nitrous Oxide; Anesthetics; Anesthetics, General; Mental Disorders; Depressive Disorder, Major; Analgesics; Analgesics, Non-Narcotic; Physiologic Effects of Drugs; Anesthetics, Inhalational
• Additional Relevant MeSH Terms: Mental Disorders; Behavioral Symptoms; Mood Disorders; Depression; Depressive Disorder; Depressive Disorder, Major; Physiological Effects of Drugs; Peripheral Nervous System Agents; Anesthetics; Central Nervous System Depressants; Sensory System Agents; Analgesics, Non-Narcotic; Analgesics; Anesthetics, General; Anesthetics, Inhalation; Nitrous Oxide
• Other Study ID Numbers: 438/19

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No