Adults 18 to 70, any sex, with COVID-19-Induced Parosmia. Patients with the condition only — healthy volunteers not accepted.
Results — posted to ClinicalTrials.gov
Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.
Parosmia Olfactory Dysfunction Outcomes RatingPrimary· 1-mo outcome and 3-mo outcome
The primary outcome of the study is to determine the efficacy of a stellate ganglion block (SGB) in improving parosmia-related quality of life compared to a saline injection placebo.
The instrument contains 28 total items with each scored on a 5-point Likert scale from 0 (no difficulty) to 4 (complete difficulty or very frequent bother).
Higher total scores indicate a greater degree of dysfunction and limitation. The minimal clinically important difference (MCID) for DisODOR being 15 points.
1-mo
Group
Value
95% CI
Experimental: Stellate Ganglion Block
9
-19 – 54
Placebo: Sham Injection
9
-13 – 82
3-mo
Group
Value
95% CI
Experimental: Stellate Ganglion Block
14
-21 – 59
Placebo: Sham Injection
11
-16 – 60
Clinical Global Impression - Severity Scale (CGI-S) Smell LossSecondary· 1-mo and 3-mo
The Clinical Global Impression - Improvement Scale (CGI-I) for smell loss (parosmia) is used to measure the overall response to treatment by assessing changes in the clinical condition compared to before the stellate ganglion block. It uses a 7-point Likert scale with the following response options: (1) Much better now than before, (2) Moderately better now than before, (3) Slightly better now than before, (4) About the same, (5) Slightly worse now than before, (6) Moderately worse now than before, and (7) Much worse now than before. Participants who report "slightly better now than before" or
At each follow-up visit, participants are asked to rank their overall improvement in each of the 11 symptoms compared to their symptoms prior to their first SGB. The improvement options are based on the CGI-I 7-point Likert scale.
Total scores range from 0-77, with higher scores being worse and lower scores being better.
Participants will be asked to complete the OCS, which measures the negative mental response to smell dysfunction loss. Multiple thoughts/feelings will be assessed on a 5-point Likert scale with a maximum score of 52.
Participants will complete the OCS at each study visit to assess the degree of olfactory-related catastrophizing over time.
1-mo
Group
Value
95% CI
Experimental: Stellate Ganglion Block
8
-6 – 32
Placebo: Sham Injection
6
-5 – 38
3-mo
Group
Value
95% CI
Experimental: Stellate Ganglion Block
7
-13 – 31
Placebo: Sham Injection
5
-8 – 33
Hospital Anxiety and Depression Scale (HADS)Secondary· 1 month, 3 months
Participants will be asked to complete the HADS, which screens for both anxiety and depression in the general population. It consists of 7 questions for anxiety and 7 questions for depression each ranked on a 4-point Likert Scale. A score of 0-7 is considered normal, 8-10 is borderline abnormal anxiety or depression, and a score of 11-21 corresponds with screening positive for anxiety or depression.
1-mo HADS anxiety
Group
Value
95% CI
Experimental: Stellate Ganglion Block
1
-6 – 10
Placebo: Sham Injection
1
-5 – 10
3-mo HADS anxiety
Group
Value
95% CI
Experimental: Stellate Ganglion Block
1
-8 – 18
Placebo: Sham Injection
1
-8 – 8
1-mo HADS depression
Group
Value
95% CI
Experimental: Stellate Ganglion Block
1
-7 – 10
Placebo: Sham Injection
1
-4 – 8
3-mo HADS depression
Group
Value
95% CI
Experimental: Stellate Ganglion Block
8
-6 – 32
Placebo: Sham Injection
3
-7 – 7
Patient Satisfaction With TreatmentSecondary· 1 mo, 3-mo
Participants will be asked at 1 month "Overall, how satisfied were you with the stellate ganglion block treatment for your parosmia?" with possible answer choices: 1) Completely dissatisfied, 2) Mostly dissatisfied, 3) Somewhat dissatisfied, 4) Neither satisfied or dissatisfied, 5) Somewhat satisfied, 6) Mostly satisfied, 7) Completely satisfied.
1-mo
Group
Value
95% CI
Experimental: Stellate Ganglion Block
8
Placebo: Sham Injection
5
Experimental: Stellate Ganglion Block
10
Placebo: Sham Injection
4
Experimental: Stellate Ganglion Block
13
Placebo: Sham Injection
7
3-mo
Group
Value
95% CI
Experimental: Stellate Ganglion Block
11
Placebo: Sham Injection
5
Experimental: Stellate Ganglion Block
1
Placebo: Sham Injection
5
Experimental: Stellate Ganglion Block
18
Placebo: Sham Injection
6
Assessment of the BlindSecondary· during first visit
Immediately after the injection, participants will be asked "Which intervention do you think you received?" with answer choices of 1) Mepivacaine (active medication) or 2) Saline (placebo).
It is performed immediately after the initial injection during the first visit, just prior to discharge.
1-mo blind assessment
Group
Value
95% CI
Experimental: Stellate Ganglion Block
18
Placebo: Sham Injection
14
3-mo blind assessment
Group
Value
95% CI
Experimental: Stellate Ganglion Block
12
Placebo: Sham Injection
4
Adverse events — posted to ClinicalTrials.gov
Time frame: Adverse events will be recorded from the time of dose administration (the stellate ganglion block or placebo injection) through the post-dose period and up to the final follow-up visit at approximately 3 months after the injection. The study team will monitor and document all adverse events throughout this entire timeframe..
Reporting threshold: 0%.
Adverse-event reports describe events observed during the trial — not all are caused by the drug.
Chronic olfactory dysfunction, both hyposmia and parosmia, from the COVID-19 pandemic is a growing public health crisis with up to 1.2 million people in the United States affected. Olfactory dysfunction impacts one's quality of life significantly by decreasing the enjoyment of foods, creating environmental safety concerns, and affecting one's ability to perform certain jobs. Olfactory loss is also an independent predictor of anxiety, depression, and even mortality. Recent research by our group (unpublished data) and suggests that parosmias, moreso than hyposmias, can result in increased rates of anxiety, depression, and even suicidal ideation. While the pandemic has increased the interest by the scientific community in combating the burgeoning health crisis, few effective treatments currently exist for olfactory dysfunction. Persistent symptoms after an acute COVID-19 infection, or "Long COVID" symptoms, have been hypothesized to be a result of sympathetic positive feedback loops and dysautonomia. Stellate ganglion blocks have been proposed to treat this hyper-sympathetic activation by blocking the sympathetic neuronal firing and resetting the balance of the autonomic nervous system. Studies prior to the COVID-19 pandemic have supported a beneficial effect of stellate ganglion blocks on olfactory dysfunction, and recent news reports and a published case series have described a dramatic benefit in both olfactory function and other long COVID symptoms in patients receiving stellate ganglion blocks. A previous pilot study using stellate ganglion blocks of 20 participants with persistent COVID-19 olfactory dysfunction resulted modest improvements in subjective olfactory function, smell identification, and olfactory-specific quality-of-life, but it lacked a control group. Therefore, we propose a double-blinded, placebo-controlled randomized clinical trial assessing the efficacy of a stellate ganglion block versus saline injection in a total of up to 140 participants with persistent COVID-19-associated olfactory dysfunction.
Publications & conference data
1 peer-reviewed publication reference this trial (live from Europe PMC):
NCT06570213 — Evaluating The Efficacy Of Combined Cognitive Processing Therapy and Stellate Ganglion Blocks for PTSD
· EARLY_PHASE1
· not yet recruiting
NCT07271615 — Effect of Preoperative Stellate Ganglion Block on Postoperative Atrial Fibrillation After Coronary Artery Bypass Graftin
· NA
· recruiting
NCT07129811 — Stellate Ganglion Block in Complex Regional Pain Syndrome
· NA
· recruiting
NCT06742255 — Stellate Ganglion Block in Longstanding Facial Nerve Palsy Patients
· not yet recruiting
NCT06646081 — The Impact of Greater Occipital Nerve and Stellate Ganglion Block Treatments on Sleep in Chronic Headache Management
· NA
· not yet recruiting
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Publications: Europe PMC API search by NCT ID, retrieved 9 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by Washington University School of Medicine
Last refreshed: 10 November 2025
Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT06253806.