Effect of Nitrous Oxide as a Treatment for Subjective, Idiopathic, Nonpulsatile Bothersome Tinnitus: A Randomized Clinical Trial

A randomized, double-blind, placebo-controlled phase 2 study of intratympanic OTO-313 in patients with moderate to severe subjective tinnitus

PURPOSE

This was a randomized, double-blind, placebo-controlled Phase 2 study to evaluate the efficacy and safety of intratympanic OTO-313 in patients with subjective unilateral tinnitus.

METHODS

Patients with moderate to severe unilateral tinnitus of 2-12 months duration were enrolled. A single intratympanic injection of OTO-313 or placebo was administered to the affected ear and patients were evaluated during a 16-weeks follow-up period. Efficacy was assessed using the Tinnitus Functional Index (TFI), daily ratings of tinnitus loudness and annoyance, and Patient Global Impression of Change (PGIC).

RESULTS

Intratympanic administration of OTO-313 and placebo produced reductions in tinnitus with a similar percentage of TFI responders at Weeks 4, 8, 12, and 16. Reductions in daily ratings of tinnitus loudness and annoyance, and PGIC scores were also similar between OTO-313 and placebo groups. No significant differences in mean TFI scores between OTO-313 and placebo were observed for pre-specified strata regarding tinnitus duration (≥ 2 to ≤ 6 months and > 6 to ≤ 12 months) and TFI baseline scores (≥ 32 to ≤ 53 points and ≥ 54 to 100 points), although the results numerically favored OTO-313 in patients in the ≥ 2 to ≤ 6 months strata. These results also demonstrated an unexpectedly high placebo response particularly amongst patients with chronic tinnitus, despite training implemented to mitigate placebo response. OTO-313 was well-tolerated with a similar incidence of adverse events compared to placebo.

CONCLUSIONS

OTO-313 did not demonstrate a significant treatment benefit relative to placebo due in part to a high placebo response. OTO-313 was safe and well-tolerated.

The efficacy and tolerability of inhaled nitrous oxide in major depressive disorder: a systematic review and meta-analysis

BACKGROUND

Nitrous oxide (N2O) has been initially confirmed by clinical trials to benefit to patients with major depressive disorder (MDD). However, there needs to be a meta-analysis to compare the efficacy and tolerability of N2O in MDD.

METHODS

PubMed, EMBASE, and Cochrane Library were searched for relevant studies up to Jan 1st, 2023. The meta-analysis mainly compared the outcome of the change in depression severity scores, response, remission, and adverse events in patients with MDD receiving 50% N2O and placebo.

RESULTS

Four studies with 133 patients were eventually identified. We found that the N2O group and control group showed an overall significant difference in the change in depression severity score for patients at 2 h, 24 h, and 2 weeks or more (2 h, SMD =  - 0.64, 95% CI - 0.01 to - 0.28, p < 0.0001) (24 h, SMD =  - 0.65, 95% CI - 1.01 to - 0.29, p < 0.0001) (2 weeks, SMD =  - 0.76, 95% CI - 1.16 to - 0.36, p < 0.0001). For the response and remission rate, the long-term effect of N2O was also statistically significant (for the response, RR = 2.33, 95% CI 1.23 to 4.44, p = 0.01) (for the remission, RR = 4.68, 95% CI 1.49 to 14.68, p = 0.008). For safety outcomes, patients treated with N2O had higher odds of nausea or vomiting (RR = 10.15, 95% CI 1.96 to 52.59, p = 0.009).

CONCLUSION

Our study suggested that N2O has a rapid and long-lasting antidepressant effect in patients with MDD. However, the efficacy of lower or titrated concentration of N2O should be further investigated.

Current Therapeutic Trends for Tinnitus Cure and Control: A Scoping Review

The present scoping review assessed knowledge updates in tinnitus management. We included randomized trials, non-randomized studies, systematic reviews, meta-analyses, and observational studies in last 5 years on patients with tinnitus using Population, Concept, and Context mnemonic. We excluded studies on tinnitus epidemiology, technique-specific comparative studies for tinnitus assessment, review articles, or case reports. We used an artificial intelligence-powered tool MaiA for overall workflow management. Data charting elements included study identifiers, study design, population, interventions used, their outcomes on tinnitus scales, and treatment recommendations if any. Charted data from selected sources of evidence was presented using tables and a concept map. We also identified five evidence-based clinical practice guidelines (CPGs) [from the United States, Europe, and Japan regions] in our review of total 506 results, 205 underwent screening based on eligibility criteria and 38 were included for the final charting. We found three major categories of interventions in our review: Medical technology therapies; Behavioural/habituation therapies; and Pharmacological, herbal/complementary, and alternative medicine therapies. Although evidence-based guidelines on tinnitus therapy did not recommend stimulation therapies, majority of the tinnitus research to date is focused on stimulation. It is highly recommended that clinicians consider CPGs when making treatment recommendations and make the distinction between established management approaches with good evidence and emerging treatment approaches for tinnitus management.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-023-03910-2.

Race/Ethnicity, Gender, and Socioeconomic Status Representation in U.S.-Based Randomized Controlled Trials of Tinnitus: A Systematic Review

PURPOSE

The purpose of this study was to investigate if peer-reviewed randomized controlled trials (RCTs) for the management/treatment of tinnitus conducted in the United States include diverse participants in terms of gender, race/ethnicity, education, occupation, and income.

METHOD

We performed a comprehensive and systematic literature search via PubMed, Web of Science, Clinical-Trials.gov, and the Cochrane Central Register of Controlled Trials. Our goal was to identify prospective RCTs of tinnitus intervention conducted in the United States from January 1994 to September 2021 and published in peer-reviewed journals.

RESULTS

A total of 2,584 studies were retrieved. Thirty-two peer-reviewed articles met all inclusion criteria. Of the included studies, approximately 96% reported participants' gender. Approximately 15% studies reported race/ethnicity information in alignment with the U.S. Census Bureau. However, an underrepresentation of both females and people of color was evident across studies. Reporting of socioeconomic status information of participants was also scarce, with only 25% studies reporting education and/or occupation of participants and 0% reporting income levels.

CONCLUSIONS

This study indicates underrepresentation and underreporting of diverse participant pools in tinnitus research. Reasons for such underrepresentation are explored. Additionally, this systematic review indicates that recent research in tinnitus portrays an optimistic trend in terms of reporting and recruitment of diverse participant groups. Sustainable strategies for including diverse research participants are essential for hearing health care equity. Research and strategies to promote this goal are discussed.

Intervention of the Syndrome-Position Point Selection Method on Idiopathic Tinnitus of Phlegm-Fire Stagnation Pattern: A Randomized Controlled Study

Objective

To investigate the clinical effect of the syndrome-position point selection method on the intervention of idiopathic tinnitus of the phlegm-fire stagnation pattern.

Methods

One hundred patients with idiopathic tinnitus of phlegm-fire stagnation pattern who met the inclusion criteria were randomized into the treatment group and the control group by the random number table method, with 50 cases in each group. The treatment group (syndrome-position point selection method) was treated with acupuncture at the corresponding acupoints for tinnitus and associated symptoms and the corresponding acupoints located in Wernicke's area of scalp projection, while the control group (traditional acupuncture method) was treated with the combination of acupuncture points with the most frequent occurrence in the tinnitus research literature for acupuncture treatment. Both groups received acupuncture twice a week for 5 weeks. The efficacy was evaluated before and after treatment with the Tinnitus Severity Inventory (TSI), Sleep Spiegel Questionnaire, Self-Rating Anxiety Scale (SAS), and Self-Rating Depression Scale (SDS).

Results

The 100 patients with idiopathic tinnitus of phlegm-fire stagnation pattern completed 5 weeks of clinical treatment and a month of follow-up with no loss of patients and no adverse event reports. Three patients recovered with the disappearance of the tinnitus symptoms in the treatment group after 5 weeks of treatment. After 5 weeks of treatment, obvious differences between the two groups were observed in the TSI scores (P < 0.05) and the Spiegel scores, with a better Spiegel score in the treatment group than in the control group (P < 0.05). Compared with the control group, the depression (SDS score) and anxiety (SAS score) of tinnitus patients in the treatment group were markedly improved (P < 0.05).

Conclusion

In line with the principle of symptomatic treatment and based on the modern imaging data, the syndrome-position point selection method is more accurate and effective compared with the traditional acupoint selection method, which significantly improves the symptoms, sleep quality, and psychological state of patients with idiopathic tinnitus of the phlegm-fire stagnation pattern.

Intratympanic Administration of OTO-313 Reduces Tinnitus in Patients With Moderate to Severe, Persistent Tinnitus: A Phase 1/2 Study

OBJECTIVE

To evaluate the safety and exploratory efficacy of intratympanic administration of OTO-313 in patients with tinnitus.

STUDY DESIGN

Single intratympanic injection of OTO-313 evaluated in a randomized, double-blind, placebo-controlled Phase 1/2 clinical study.

SETTING

Tertiary referral centers.

PATIENTS

Patients with unilateral tinnitus (moderate-severe) with tinnitus duration 1 to 6 months.

INTERVENTIONS

Intratympanic OTO-313.

MAIN OUTCOME MEASURES

Safety and change from baseline in tinnitus functional index (TFI), daily ratings of tinnitus loudness and annoyance, and patient global impression of change (PGIC).

RESULTS

OTO-313 was well-tolerated with lower incidence of adverse events than placebo. Mean TFI reduction from baseline favored OTO-313 at Week 2, 4, and 8. A clinically meaningful, 13-point improvement on the TFI was observed in 43% (6/14) of OTO-313 patients at both Weeks 4 and 8 versus 13% (2/16) of placebo patients (ad hoc responder analysis, p-value < 0.05). Reductions in daily ratings of tinnitus loudness and annoyance favored OTO-313 compared with placebo. In OTO-313 responders, a strong correlation existed between change from baseline in TFI score and changes in tinnitus loudness, tinnitus annoyance, and PGIC.

CONCLUSIONS

OTO-313 was well-tolerated and demonstrated a higher proportion of responders than placebo across consecutive visits (Weeks 4 and 8) supporting further clinical development of OTO-313 for the treatment of tinnitus.

A phase 2 trial of inhaled nitrous oxide for treatment-resistant major depression

Nitrous oxide at 50% inhaled concentration has been shown to improve depressive symptoms in patients with treatment-resistant major depression (TRMD). Whether a lower concentration of 25% nitrous oxide provides similar efficacy and persistence of antidepressant effects while reducing the risk of adverse side effects is unknown. In this phase 2 clinical trial (NCT03283670), 24 patients with severe TRMD were randomly assigned in a crossover fashion to three treatments consisting of a single 1-hour inhalation with (i) 50% nitrous oxide, (ii) 25% nitrous oxide, or (iii) placebo (air/oxygen). The primary outcome was the change on the Hamilton Depression Rating Scale (HDRS-21). Whereas nitrous oxide significantly improved depressive symptoms versus placebo (P = 0.01), there was no difference between 25 and 50% nitrous oxide (P = 0.58). The estimated differences between 25% and placebo were -0.75 points on the HDRS-21 at 2 hours (P = 0.73), -1.41 points at 24 hours (P = 0.52), -4.35 points at week 1 (P = 0.05), and -5.19 points at week 2 (P = 0.02), and the estimated differences between 50% and placebo were -0.87 points at 2 hours (P = 0.69), -1.93 points at 24 hours (P = 0.37), -2.44 points at week 1 (P = 0.25), and -7.00 points at week 2 (P = 0.001). Adverse events declined substantially with dose (P < 0.001). These results suggest that 25% nitrous oxide has comparable efficacy to 50% nitrous oxide in improving TRMD but with a markedly lower rate of adverse effects.

Methodological Aspects of Randomized Controlled Trials for Tinnitus: A Systematic Review and How a Decision Support System Could Overcome Barriers

Although a wide range of tinnitus management interventions is currently under research and a variety of therapeutic interventions have already been applied in clinical practice, no optimal and universal tinnitus treatment has been reached yet. This fact is to some extent a consequence of the high heterogeneity of the methodologies used in tinnitus related clinical studies. In this manuscript, we have identified, summarized, and critically appraised tinnitus-related randomized clinical trials since 2010, aiming at systematically mapping the research conducted in this area. The results of our analysis of the 73 included randomized clinical trials provide important insight on the identification of limitations of previous works, methodological pitfalls or gaps in current knowledge, a prerequisite for the adequate interpretation of current literature and execution of future studies.

Emerging Topics in the Behavioral Neuroscience of Tinnitus

This volume has highlighted the many recent advances in tinnitus theory, models, diagnostics, therapies, and therapeutics. But tinnitus knowledge is far from complete. In this chapter, contributors to the Behavioral Neuroscience of Tinnitus consider emerging topics and areas of research needed in light of recent findings. New research avenues and methods to explore are discussed. Issues pertaining to current assessment, treatment, and research methods are outlined, along with recommendations on new avenues to explore with research.