Testing Ondansetron for vasovagal syncope (VVS)
Official title: A Proof of Principle Study of Ondansetron for the Prevention of Vasovagal Syncope: The Eleventh Prevention of Syncope Trial (POST11)
- Phase 2
- 2 groups
- One site, in Calgary
- Recruiting
Interventions
- Medication
Ondansetron
Serotonin antagonists (5-HT3 antagonists) (Carbazole Derivative)
- Medication
Placebo
Matching placebo identical in appearance.
Canadian Sites (1)
1 of 1 recruiting
- Recruiting
University of Calgary
Calgary, Alberta
Eligibility Criteria
See who this study is looking for12 criteria
The trial’s own eligibility text, word for word from the registry. Only the trial site can say who takes part.
Inclusion
- +(A) ≥1 syncopal spells in the year preceding enrolmentEnrolmentThe number of participants a study plans to include, or has included.Read more → (B) ≥-2 points on the Calgary Syncope Symptom Score( Accurate Calculation for Diagnosis of Vasovagal Syncope) (C) Age ≥18 years with informed consentInformed consentThe process of being told what taking part involves, then choosing freely.Read more →
Exclusion
- −other causes of syncope, such as ventricular tachycardia, complete heart block, orthostatic hypotension or hypersensitive carotid sinus syndrome
- −Known hypersensitivity to ondansetron and related medications
- −an inability to give informed consentInformed consentThe process of being told what taking part involves, then choosing freely.Read more →
- −important valvular, coronary, myocardial or conduction abnormality or significant arrhythmia
- −hypertrophic cardiomyopathy
- −a permanent pacemaker
- −a seizure disorder
- −hypertension defined as \>160/90 mm Hg
- −lactating women
- −medications with known effects on BP
- −other factors which, in the investigatorPrincipal investigatorThe doctor or researcher responsible for running the study at a site.Read more →'s opinion, would prevent the subject from completing the protocolProtocolThe detailed plan a study must follow.Read more →.
In plain language
Assembled directly from this trial’s registry record. Every sentence traces to a field below — nothing here is generated or interpreted.
What this study is
This study is testing a treatment for a condition.
Phase 2Phase 2A middle-stage study looking at what a treatment does and watching for side effects.Read more → — a middle-stage study in a few hundred people at most, looking at what the treatment does and watching for side effectsSide effectAn unwanted effect thought to be caused by the treatment itself.Read more →.
From the trial registry
Built from these fields:
- designModule.designInfo.primaryPurpose
- designModule.phases
Who receives what
There are 2 groups in this study.
Group A, the comparison group, receives Ondansetron.
Registry label: A: Ondansetron
Group B, the comparison group, receives PlaceboPlaceboA dummy treatment with no active medicine, used for comparison.Read more →.
Registry label: B: Placebo
From the trial registry
Built from these fields:
- armsInterventionsModule.armGroups[].label
- armsInterventionsModule.armGroups[].type
- armsInterventionsModule.armGroups[].interventionNames
How the study is run
Which group you would be placed in is decided by chance, like a coin flip — not by you and not by your doctor.
You, the study team, the people giving the treatment, and the people analysing the results would all be kept unaware of which group you are in until the study ends.
From the trial registry
Built from these fields:
- designModule.designInfo.allocation
- designModule.designInfo.maskingInfo.masking
Is there a placebo?
One group receives a placeboPlaceboA dummy treatment with no active medicine, used for comparison.Read more → — a dummy treatment with no active medicine in it — alongside the other treatment that group is given.
One group receives an existing treatment, so the two can be compared.
From the trial registry
Built from these fields:
- armsInterventionsModule.armGroups[].type
- armsInterventionsModule.armGroups[].interventionNames
Who the study is looking for
The study lists an age range of 18 years to 100 years.
The study is open to people of any sex.
The study does not accept healthy volunteersHealthy volunteerSomeone without the condition being studied who takes part anyway.Read more →.
These are the criteria the study lists. Only the trial siteTrial siteA hospital or clinic where a study is actually run.Read more → can decide whether someone can take part.
From the trial registry
Built from these fields:
- eligibilityModule.minimumAge
- eligibilityModule.maximumAge
- eligibilityModule.sex
- eligibilityModule.healthyVolunteers
How big and how long
The study aims to enrol about 70 people.
The study is currently expected to finish around December 2026.
The main measurement is taken over: 1 hour.
From the trial registry
Built from these fields:
- designModule.enrollmentInfo.count
- statusModule.completionDateStruct.date
- outcomesModule.primaryOutcomes[].timeFrame
What the study measures
Time to syncope or presyncope — measured over 1 hour.
From the trial registry
Built from these fields:
- outcomesModule.primaryOutcomes[].measure
- outcomesModule.primaryOutcomes[].timeFrame
Source: NCT05755737 on ClinicalTrials.gov. The full registry text is further down this page — this summary never replaces it.
Not medical advice. What do these terms mean?
What is being tested — in plain terms
About OndansetronDrug
Serotonin antagonists (5-HT3 antagonists) (Carbazole Derivative)
From the trial registry — its own words, unedited.
What a drug is here: A medicine — a chemical or small-molecule treatment — given as the thing being studied.
Read the full explanation → · in clinical review
About PlaceboDrug
Matching placebo identical in appearance.
From the trial registry — its own words, unedited.
What a drug is here: A medicine — a chemical or small-molecule treatment — given as the thing being studied.
Read the full explanation → · in clinical review
Common questions
Answered from this trial’s registry record. Where the record doesn’t say, these answers say so rather than filling the gap.
Am I eligible for this trial?
Only the trial siteTrial siteA hospital or clinic where a study is actually run.Read more → can decide whether someone can take part. Concord cannot make that determination, and neither can any tool that has not examined you.
What the study lists: an age range of 18 years to 100 years.
The full inclusionInclusion criteriaThe things you must have or be for a study to consider you.Read more → and exclusion criteriaExclusion criteriaThe things that would prevent someone from taking part.Read more → are published on this page, exactly as the study team wrote them.
The useful next step is to bring this trial to your doctor. Answering a few questions first gives them something concrete to review.
From the trial registry
- eligibilityModule.minimumAge
- eligibilityModule.maximumAge
- eligibilityModule.eligibilityCriteria
Is there a placebo?
Yes. One group receives a placeboPlaceboA dummy treatment with no active medicine, used for comparison.Read more → — a dummy treatment with no active medicine in it — alongside the other treatment that group is given.
One group receives an existing treatment so the two can be compared.
From the trial registry
- armsInterventionsModule.armGroups[].type
Would I know which treatment I am getting?
You, the study team, the people giving the treatment, and the people analysing the results would all be kept unaware of which group you are in until the study ends.
Which group you would be placed in is decided by chance, like a coin flip — not by you and not by your doctor.
From the trial registry
- designModule.designInfo.maskingInfo.masking
- designModule.designInfo.allocation
Who can join?
The study lists an age range of 18 years to 100 years.
It is open to people of any sex.
It does not accept healthy volunteersHealthy volunteerSomeone without the condition being studied who takes part anyway.Read more →.
Only the trial siteTrial siteA hospital or clinic where a study is actually run.Read more → can confirm whether a particular person can take part.
From the trial registry
- eligibilityModule.minimumAge
- eligibilityModule.maximumAge
- eligibilityModule.sex
- eligibilityModule.healthyVolunteers
How long would this take?
The study's main measurement is taken over: 1 hour.
The study as a whole is currently expected to finish around 2026-12-31.
How long any one person takes part can differ from the study length. The study team can tell you what the schedule looks like in practice.
From the trial registry
- outcomesModule.primaryOutcomes[].timeFrame
- statusModule.completionDateStruct.date
How many people are taking part?
The study aims to enrol about 70 people.
From the trial registry
- designModule.enrollmentInfo.count
Where is this happening?
This study lists one location: Calgary, Alberta, Canada.
Sites can open and close during a study, so confirm with the team before travelling.
From the trial registry
- trial_locations
About This Trial
About 20% of adults faint recurrently. These patients are often highly symptomatic, have problems with employment and driving, can be injured, and have poor quality of life. There are few therapies that have withstood the test of randomized clinical trials. the investigators will conduct a prospective, randomized, parallel, double-blind, proof-of-concept study that tests the hypothesis that serotonin 5HT3 receptor inhibition with ondansetron prevents tilt-induced vasovagal syncope (VVS) and pre-syncope in patients with clinical VVS. A total of 70 patients with quantitative clinical diagnostic criteria for VVS and at least 1 syncopal spell in the preceding year will be randomized in a double-blind acute phase 2 study to ondansetron 8 mg PO BID x 2 doses or matching placebo. The endpoint will be presyncope or syncope associated with diagnostic hemodynamic changes. These data should provide useful preliminary data as a foundation on which to conduct a subsequent randomized clinical trial.
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See if this trial could fit youThis page is for informational purposes only and does not constitute medical advice. Clinical trial eligibility can only be determined by the trial site after proper screening. Trial information is sourced from ClinicalTrials.gov and may not reflect the most current status. Always consult your healthcare provider before making decisions about clinical trial participation.