Using Ondansetron to Prevent Fainting Episodes

A Proof of Principle Study of Ondansetron for the Prevention of Vasovagal Syncope: The Eleventh Prevention of Syncope Trial (POST11)

Phase 2 Interventional University of Calgary · NCT05755737

This study is testing if the medication ondansetron can help adults who frequently faint feel better and prevent future fainting spells.

Quick facts

PhasePhase 2
Study typeInterventional
Enrollment70 (estimated)
Ages18 Years to 100 Years
SexAll
SponsorUniversity of Calgary Academic / other
Locations1 site (Calgary, Alberta)
Trial IDNCT05755737 on ClinicalTrials.gov

What this trial studies

This clinical trial investigates the effectiveness of ondansetron, a serotonin 5HT3 receptor inhibitor, in preventing vasovagal syncope (VVS) in adults who have experienced recurrent fainting spells. The study will involve 70 participants who meet specific diagnostic criteria for VVS and will be randomized to receive either ondansetron or a placebo in a double-blind manner. Participants will undergo a tilt table test to assess the drug's impact on syncope and presyncope episodes, with continuous monitoring of heart rhythm and blood pressure. The results aim to provide preliminary data for future larger-scale trials.

Who should consider this trial

Good fit: Ideal candidates are adults aged 18 and older who have experienced at least one syncopal spell in the past year and meet specific diagnostic criteria for vasovagal syncope.

Not a fit: Patients with other causes of syncope, significant cardiovascular issues, or those who are pregnant or lactating may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could significantly reduce the frequency of fainting episodes and improve the quality of life for patients suffering from vasovagal syncope.

How similar studies have performed: While there are few established therapies for vasovagal syncope, this approach using ondansetron is novel and has not been extensively tested in this context.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

(A) ≥1 syncopal spells in the year preceding enrolment (B) ≥-2 points on the Calgary Syncope Symptom Score( Accurate Calculation for Diagnosis of Vasovagal Syncope) (C) Age ≥18 years with informed consent

Exclusion Criteria:

1. other causes of syncope, such as ventricular tachycardia, complete heart block, orthostatic hypotension or hypersensitive carotid sinus syndrome
2. an inability to give informed consent
3. important valvular, coronary, myocardial or conduction abnormality or significant arrhythmia
4. hypertrophic cardiomyopathy
5. a permanent pacemaker
6. a seizure disorder
7. hypertension defined as \>160/90 mm Hg
8. pregnancy
9. lactating women
10. glaucoma
11. medications with known effects on BP
12. Known hypersensitivity to ondansetron and related medications
13. other factors which, in the investigator's opinion, would prevent the subject from completing the protocol.

Where this trial is running

Calgary, Alberta

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions Vasovagal SyncopeSyncopeOndansetron
Last reviewed 2026-06-09 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.