FibromyalgiaPhase 2NCT05357066
Nitrous Oxide as Treatment for Fibromyalgia
A Phase 2 study testing Nitrous oxide gas for inhalation in people with Fibromyalgia and Central Neuropathic Pain, run by University of Chicago at 1 site in United States.
Trial summary
The purpose of this study is to explore a potential role of nitrous oxide in treating pain associated with fibromyalgia. Read more about this study
- Who is it for?
- Ages 18 to 75 yearsHealthy volunteers can take part
- Conditions the study is for
- Fibromyalgia, Central Neuropathic Pain
- What is being tested?
- Nitrous oxide gas for inhalation
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 0 participants
- Where
- 1 siteUnited States
- Study dates
- 12 Nov 2021to 27 Feb 2026
- Phase
- Phase 2
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 75 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- 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.
Who cannot join
- 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.
Show all 9Show fewer
- 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.
Trial locations and contacts
1 site in 1 country.
About this study
The purpose of this study is to explore a potential role of nitrous oxide in treating pain associated with fibromyalgia.
Read the 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)
- Conditions
- Fibromyalgia, Central Neuropathic Pain
- Being tested
- Nitrous oxide gas for inhalation, Placebo
- Keywords
- Fibromyalgia, Pain
- Medical subject headings
- Fibromyalgia, Pain
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Nitrous oxide gas for inhalationDrug
Also called Nitrous Oxide, Nitrous, N2O, Laughing gas
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.
PlaceboDrug
Also called Sham
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.
| Study group | Role | What they receive |
|---|---|---|
| Treatment; Nitrous Oxide 50% | Active comparator | A single 60-minute session of inhaled 50% nitrous oxide. Receives: Drug: Nitrous oxide gas for inhalation |
| Control; Oxygen-air mixture | Placebo comparator | A single 60-minute session of inhaled Oxygen-air mixture Receives: Drug: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
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.
Measured: Over 8-weeks from baseline (length of study participation)
Secondary outcomes (4)
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.
Measured: 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']
Measured: 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
Measured: 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
Measured: Over 8-weeks from baseline (length of study participation)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted2 May 2022
- Study start12 Nov 2021
- Primary completion27 Feb 2026
- Study completion27 Feb 2026
Why it stopped: PI has left university
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (8)Papers the sponsor has linked to this study.
- Other trials for FibromyalgiaStudies of the same condition, open and under way.
- More trials run by University of ChicagoThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- Participants are randomly assigned to a treatment group schedule, group-1 (nitrous, placebo), or group-2 (placebo, nitrous). Dosing consists of 50% Nitrous oxide in oxygen mixture (FiO2 0.5) vs placebo (oxygen-air mixture FiO2 ≈0.3).
- Masking
- Double blind
- Who is masked
- Participant, Outcomes assessor
- Enrolment
- 0 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Chicago
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Peter Nagele, MD, MSc, Principal investigator, University of Chicago, Department of Anesthesia and Critical Care
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05357066
- Sponsor's protocol ID
- IRB20-1169
- Status last verified
- May 2026
- First submitted
- 9 Nov 2021
- Last updated
- 14 May 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
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.
PubMed 22560527Clauw 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.
PubMed 21878603Sorensen 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.
PubMed 8610220Sorensen 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.
PubMed 9263160Noppers 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.
PubMed 21482474Graven-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.
PubMed 10781923Jevtovic-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.
PubMed 9546794Nagele 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.
PubMed 15159532
Study at a glance
From the registry record, last updated by the sponsor on 14 May 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Nitrous Oxide as Treatment for Fibromyalgia
- ClinicalTrials.gov ID
- NCT05357066
- Acronym / sponsor ID
- IRB20-1169
- Conditions
- Fibromyalgia, Central Neuropathic Pain
- Keywords
- Fibromyalgia, Pain
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- WithdrawnReason stopped: PI has left university
- Enrolment
- 0 participants (actual)
- Lead sponsor
- University of ChicagoUniversity, hospital or other
- Study start
- 12 Nov 2021 (actual)
- Primary completion
- 27 Feb 2026 (actual)
- Study completion
- 27 Feb 2026 (actual)
- First posted
- 2 May 2022 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The purpose of this study is to explore a potential role of nitrous oxide in treating pain associated with fibromyalgia.
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 design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Double blind (participant, outcomes assessor)
- Number of arms
- 2
- Model description
- Participants are randomly assigned to a treatment group schedule, group-1 (nitrous, placebo), or group-2 (placebo, nitrous). Dosing consists of 50% Nitrous oxide in oxygen mixture (FiO2 0.5) vs placebo (oxygen-air mixture FiO2 ≈0.3).
| Arm | Type | Receives |
|---|---|---|
| Treatment; Nitrous Oxide 50% | Active comparator | Drug: Nitrous oxide gas for inhalationA single 60-minute session of inhaled 50% nitrous oxide. |
| Control; Oxygen-air mixture | Placebo comparator | Drug: PlaceboA single 60-minute session of inhaled Oxygen-air mixture |
Who may qualify
- Ages
- 18 to 75 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (6 listed)
- 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
Key exclusion criteria (9 listed)
- 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.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Nitrous oxide gas for inhalationAlso: Nitrous Oxide, Nitrous, N2O, Laughing gasAdministration 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. | Drug | Treatment; Nitrous Oxide 50% |
| PlaceboAlso: ShamAdministration 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. | Drug | Control; Oxygen-air mixture |
Primary outcome
Monitor changes in NPRS score
Time frame: Over 8-weeks from baseline (length of study participation)
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.
4 secondary outcomes
Changes in FIQR
Time frame: Over 8-weeks from baseline (length of study participation)
Changes in Global Impression of Change Scale
Time frame: Over 8-weeks from baseline (length of study participation)
Computerize Adaptive Testing - Mental Health (CAT-MH) measurements
Time frame: Over 8-weeks from baseline
Hospital Anxiety and Depression Scale
Time frame: Over 8-weeks from baseline (length of study participation)
Results and safety
The study was withdrawn before enrolling participants, so there are no results.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 14 May 2026.
- Background: PubMed 22560527Arnold 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.
- Background: PubMed 21878603Clauw 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.
- Background: PubMed 8610220Sorensen 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.
- Background: PubMed 9263160Sorensen 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.
- Background: PubMed 21482474Noppers 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.
- Background: PubMed 10781923Graven-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.
- Background: PubMed 9546794Jevtovic-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.
- Background: PubMed 15159532Nagele 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.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Peter Nagele, MD, MSc principal investigator
University of Chicago, Department of Anesthesia and Critical Care
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing Nitrous oxide gas for inhalation in people with Fibromyalgia and Central Neuropathic Pain, run by University of Chicago at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: withdrawn, as of the sponsor's last update on 14 May 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
The study was withdrawn before enrolling participants, so there are no results.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Monitor changes in NPRS score (time frame: Over 8-weeks from baseline (length of study participation)). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT05357066, which also lists 8 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 14 May 2026.