Nitrous Oxide as Treatment for Fibromyalgia

The purpose of this study is to explore a potential role of nitrous oxide in treating pain associated with fibromyalgia.

Study Overview

• Status: Withdrawn
• Conditions: Fibromyalgia; Central Neuropathic Pain
• Intervention / Treatment: Drug: Nitrous oxide gas for inhalation; Drug: Placebo

Detailed Description

Investigators are conducting this trial to determine the efficacy of nitrous oxide on fibromyalgia, a chronic, debilitating, disorder typified by widespread musculoskeletal pain, accompanied by symptoms of fatigue, affected sleep, memory issues, and mood disorders.

Studies suggests that the chronic widespread pain seen in fibromyalgia patients has a neurogenic origin. Higher levels of ascending pathway neurochemicals, including nerve growth factor, substance P, and brain derived neurotrophic factor, are present in the cerebrospinal fluid (CSF) of fibromyalgia patients when compared to healthy controls. In addition, glutamate levels can be elevated in both the CSF and brain of fibromyalgia patients. Glutamate may play a central role, by acting on the NMDA-receptors to increase the central amplification of pain perception, which is thought to manifest as allodynia and hyperalgesia in fibromyalgia patients. NMDA-receptors are thus an attractive target for fibromyalgia therapeutic drug development.

In four other randomized controlled trial(s) to evaluate ketamine an NMDA-receptor antagonist; two demonstrated an acute reduction in VAS pain scores (20- to -25 points) 90- to 120-minutes following IV ketamine 0.3 mg/kg compared with placebo; while the other two using different drug concentrations and dose regimen (0.3 mg/kg over 30 minutes and 0.5 mg/kg for 3 hours) showed a 0.5- to 0.9-point reduction in pain scores (10-cm VAS) at 90 to 180 minutes following IV ketamine compared with placebo. Although all four trials demonstrated significant acute pain improvement during and immediately following the infusions, there were no sustained improvements.

Given nitrous oxide is another drug with known NMDA-receptor antagonism, this trial will evaluate the efficacy of inhaled 50% nitrous oxide compared to placebo (oxygen-air mixture). Study participants with a clinical diagnosis of fibromyalgia, meeting 2016-Fibromyalgia Diagnostic Criteria (2016-ACR) and neuropathic pain criterion will be randomly assigned to receive two, 60-minute inhalation sessions (50% nitrous oxide and placebo).

Treatment outcomes will be monitored using diagnostic tools measuring functionality, pain, and mood:

• Numeric Pain Rating Scale (NPRS)
• Revised Fibromyalgia Impact Questionnaire (FIQR)
• Patients Global Impression of Change Scale (PGIC)
• Hospital Anxiety and Depression Scale (HADS)
• Computerized Adaptive Test-Mental Health (CAT-MH)

• Study Type: Interventional
• Phase: Phase 2

Contacts and Locations

Study Locations

• United States
  • Illinois
    • Chicago, Illinois, United States, 60637
      • University of Chicago

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 75 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• 2016 American College of Rheumatology Revised criteria for fibromyalgia (2016-ACR)
• Subjects 18 -75 years of age.
• Self-reported pain of at least 4 on the Numeric Pain Rating Scale (NPRS) at screening and baseline.
• Subject receives and agrees to remain on their stable fibromyalgia treatment plan established at least 4 weeks prior to dosing. Stable means no change in dose or any pain medication.
• Ability to understand the requirements of the study, provide written informed consent, abide by the study restrictions, and agree to return for the required assessments
• If currently on psychotherapy, it must have been maintained at the same frequency for 4 weeks prior to treatment.

Exclusion Criteria:

• Unstable doses of allowed antidepressants or muscle relaxants or dosages for any other medical condition.
• Pain due to concurrent autoimmune or inflammatory disease such as rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease, or other chronic widespread pain condition(s) that may confound fibromyalgia pain.
• Psychiatric or cognitive disorder (e.g., current schizophrenia, severe depression, suicidal ideation, dementia, etc.) that the investigator or sponsor considers significant for this study.
• Clinically significant alcohol or other substance abuse within the last 2 years, in the opinion of the investigator.
• Current or recent history of medically inappropriate or illegal use of drugs of abuse including benzodiazepines, opiates, cocaine, cannabinoids, and amphetamines.
• Current treatment with N-methyl-D-aspartate receptor (NMDAR) ligands including ketamine, amantadine, dextromethorphan, memantine, methadone, or dextropropoxyphene.
• Subjects who are pregnant, breast feeding, or planning to become pregnant during the course of the study and for 28 days after the final administration of investigational product.
• Any other serious medical condition affecting heart, lung or any other organ system.
• Any impairment, activity or situation that in the judgment of the investigator would prevent satisfactory completion of the study protocol.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Treatment; Nitrous Oxide 50%; A single 60-minute session of inhaled 50% nitrous oxide.	Drug: Nitrous oxide gas for inhalation; Administration of inhaled 50% nitrous oxide in oxygen (FiO2 0.5) 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.; Other Names: N2O; Laughing gas; Nitrous Oxide; Nitrous
Placebo Comparator: Control; Oxygen-air mixture; A single 60-minute session of inhaled Oxygen-air mixture	Drug: Placebo; Administration of the placebo (oxygen-air mixture [FiO2 ≈0.3]), 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.; Other Names: Sham

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Monitor changes in NPRS score	Monitoring changes in 'Numeric Pain Rating Scale' (NPRS) diagnostic score to determine effectiveness a 60-minute session of inhaled 50% nitrous oxide vs placebo has on symptoms associated with fibromyalgia. The NPRS is a validated self-report diagnostic asking patients to indicate the intensity of current, best, and worst pain levels over the past 24 hours on a scale of 0 (no pain) to 10 (worst pain imaginable). Response and remission will be based on a 30% improvement in average daily mean (max and min) NPRS score.	Over 8-weeks from baseline (length of study participation)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in FIQR	Evaluation of response and remission will be based on 'Fibromyalgia Impact Questionnaire-Revised' (FIQR). This validated self-report diagnostic contains 21-questions to rate fibromyalgia effects over the prior 7-days. Domain 1: 9-questions rating function: 'No difficulty = 0' to 'Very difficult = 10' Domain 2: 2-questions rating overall impact: 'Never = 0' to 'Always = 10' Domain 3: 10-questions rating symptom intensity: 'None = 0' to 'Worst = 10'; First: Sum the scores for each of the 3 domains (function, overall, and symptoms).; Second: Divide domain 1 score by 3, leave domain 2 score unchanged, and divide domain 3 score by 2.; Third: Add the 3 resulting domain scores to obtain the total FIQR score.	Over 8-weeks from baseline (length of study participation)
Changes in Global Impression of Change Scale	The Global Impression of Change Scale (PGI-C), a two question, self-report diagnostic evaluating the patients belief of treatment efficacy. - Patients rate their neuropathic pain ['No pain = 0' to 'Worst = 10'], and evaluate treatment effectiveness ['Very Much Improved'; 'Much Improved'; 'Minimally'; 'Improved'; 'No Change'; 'Minimally Worse'; 'Much Worse'; 'Very Much Worse']	Over 8-weeks from baseline (length of study participation)
Computerize Adaptive Testing - Mental Health (CAT-MH) measurements	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 8-weeks from baseline
Hospital Anxiety and Depression Scale	The Hospital Anxiety and Depression Scale (HADS) is a self-report questionnaire comprising of 14-questions (7-anxiety and 7-depression), with response scores ranging: '0' to '3'; Sum Depression scores = 0 to 21; Sum Anxiety scores = 0 to 21 Score range for each item (depression and anxiety): 0-7 = Normal 8-10 = Borderline abnormal (mild) 11-14 = Abnormal (moderate) 15-21 = Severe	Over 8-weeks from baseline (length of study participation)

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Adverse events	AEs such as nausea and vomiting; or any other AEs determined probably, possibly, or unrelated to the study intervention. Study patient safety is monitored by the investigators (MD) with experience in critical care anesthesia, as well as an experienced clinical research team responsible for recording and reporting events.	Over 8-weeks (length of study participation)

Collaborators and Investigators

• Sponsor: University of Chicago
• Investigators: Principal Investigator: Peter Nagele, MD, MSc, University of Chicago, Department of Anesthesia and Critical Care

Publications and helpful links

General Publications

• Jevtovic-Todorovic V, Todorovic SM, Mennerick S, Powell S, Dikranian K, Benshoff N, Zorumski CF, Olney JW. Nitrous oxide (laughing gas) is an NMDA antagonist, neuroprotectant and neurotoxin. Nat Med. 1998 Apr;4(4):460-3. doi: 10.1038/nm0498-460.
• Graven-Nielsen T, Kendall SA, Henriksson KG, Bengtsson M, Sorensen J, Johnson A, Gerdle B, Arendt-Nielsen L. Ketamine reduces muscle pain, temporal summation, and referred pain in fibromyalgia patients. Pain. 2000 Apr;85(3):483-491. doi: 10.1016/S0304-3959(99)00308-5.
• Nagele P, Metz LB, Crowder CM. Nitrous oxide (N(2)O) requires the N-methyl-D-aspartate receptor for its action in Caenorhabditis elegans. Proc Natl Acad Sci U S A. 2004 Jun 8;101(23):8791-6. doi: 10.1073/pnas.0402825101. Epub 2004 May 24.
• Clauw DJ, Arnold LM, McCarberg BH; FibroCollaborative. The science of fibromyalgia. Mayo Clin Proc. 2011 Sep;86(9):907-11. doi: 10.4065/mcp.2011.0206.
• Noppers I, Niesters M, Swartjes M, Bauer M, Aarts L, Geleijnse N, Mooren R, Dahan A, Sarton E. Absence of long-term analgesic effect from a short-term S-ketamine infusion on fibromyalgia pain: a randomized, prospective, double blind, active placebo-controlled trial. Eur J Pain. 2011 Oct;15(9):942-9. doi: 10.1016/j.ejpain.2011.03.008. Epub 2011 Apr 11.
• Sorensen J, Bengtsson A, Backman E, Henriksson KG, Bengtsson M. Pain analysis in patients with fibromyalgia. Effects of intravenous morphine, lidocaine, and ketamine. Scand J Rheumatol. 1995;24(6):360-5. doi: 10.3109/03009749509095181.
• Arnold LM, Clauw DJ, Dunegan LJ, Turk DC; FibroCollaborative. A framework for fibromyalgia management for primary care providers. Mayo Clin Proc. 2012 May;87(5):488-96. doi: 10.1016/j.mayocp.2012.02.010.
• Sorensen J, Bengtsson A, Ahlner J, Henriksson KG, Ekselius L, Bengtsson M. Fibromyalgia--are there different mechanisms in the processing of pain? A double blind crossover comparison of analgesic drugs. J Rheumatol. 1997 Aug;24(8):1615-21.

Study record dates

Study Major Dates

• Study Start (Actual): November 12, 2021
• Primary Completion (Actual): February 27, 2026
• Study Completion (Actual): February 27, 2026

Study Registration Dates

• First Submitted: November 9, 2021
• First Submitted That Met QC Criteria: April 26, 2022
• First Posted (Actual): May 2, 2022

Study Record Updates

• Last Update Posted (Actual): May 14, 2026
• Last Update Submitted That Met QC Criteria: May 11, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Pain; Fibromyalgia
• Additional Relevant MeSH Terms: Neurologic Manifestations; Musculoskeletal Diseases; Nervous System Diseases; Muscular Diseases; Neuromuscular Diseases; Rheumatic Diseases; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Pain; Fibromyalgia; Vasodilator Agents; Circulatory and Respiratory Physiological Phenomena; Pharmacologic Actions; Chemical Actions and Uses; Therapeutic Uses; Inorganic Chemicals; Nitrogen Compounds; Oxides; Oxygen Compounds; Respiratory Mechanics; Respiration; Respiratory Physiological Phenomena; Gases; Nitrogen Oxides; Cardiovascular Agents; Nitrous Oxide; salicylhydroxamic acid; Inhalation; Endothelium-Dependent Relaxing Factors
• Other Study ID Numbers: IRB20-1169

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.: Yes