Trial results
AI generated results summary. Written by an AI model from the official source data and checked on a sample basis. It can contain mistakes, so confirm anything important against the original source. How we use AI
According to the results reported on ClinicalTrials.gov, this trial looked at whether sildenafil (compared to a placebo, or dummy pill) had any effect on fatigue in a small group of participants. A total of 12 people took part — 6 in the sildenafil group and 6 in the placebo group. By the end of the study, 5 people in the sildenafil group and all 6 in the placebo group had completed the trial; one person in the sildenafil group did not finish. The main thing being measured was a change in something called the Fatigue Impact Scale — a questionnaire with 42 questions where people rate how much fatigue affects their daily life. Scores can range from 0 (no impact at all) to 148 (the most severe impact). The reported data shows that, after 6 weeks, the sildenafil group's average score went down by 32.6 points, while the placebo group's average score went down by 1.5 points. A lower score means less reported impact from fatigue. No secondary outcome data was reported in the submitted results. It is worth noting that this was a very small trial — just 12 people in total — which means these numbers should be interpreted with great caution. These are the results as reported to ClinicalTrials.gov. They are not medical advice — always discuss what they mean for you with your doctor.
View full results on ClinicalTrials.gov ↗
These are the results as reported to ClinicalTrials.gov, not medical advice. Verify independently with the trial site and discuss what they mean for you with your doctor.
Phase 4 Chronic Fatigue Syndrome Trial, Completed
Who may be able to join
AI generated eligibility summary. Written by an AI model from the official source data and checked on a sample basis. It can contain mistakes, so confirm anything important against the original source. How we use AI
Who might be able to join this trial:
- You have been diagnosed with Chronic Fatigue Syndrome (CFS) based on the official CDC definition.
- You are of any race, ethnicity, background, or gender.
- You are over 18 years old.
- You are under 50 years old.
- You are able to understand and agree to the study terms (give informed consent).
- You are willing to stop all medicines and supplements for up to 3 weeks before the study begins.
- You have a mental health condition that started after your fatigue symptoms began, and you are able to safely stop your medications for the study period.
- You also have fibromyalgia, as long as you also meet the full diagnosis for CFS.
Who may not be able to join:
- You have a physical disability that would prevent you from taking part in study activities.
- You are currently taking any prescription medicines or supplements, including vitamins and herbal products (only regular aspirin or acetaminophen are allowed).
- You have an existing health condition such as heart disease, high blood pressure, cancer, hormone disorders, seizures, or severe obesity (confirm with trial site).
- You have a serious mental health condition such as bipolar disorder, schizophrenia, or dementia, or have had alcohol or substance abuse problems in the past year.
- You currently misuse illegal drugs or drink heavily.
- You are pregnant, due to radiation exposure from the brain scans used in this study.
- You have an abnormal heart tracing (EKG).
- You have abnormal results on certain blood tests, including thyroid, HIV, and other markers (confirm with trial site).
Important: Always verify eligibility with the trial site directly before applying.
Based on publicly available eligibility criteria from ClinicalTrials.gov. Verify directly with the trial site before acting. This is not medical advice.
GP referral letter
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Trial details
Where this trial is recruiting
Primary endpoints
Change in Fatigue Impact Scale at 6 Weeks
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Data last synced from ClinicalTrials.gov: 28 July 2026. Trial status can change. Always verify current status directly with the trial site before making any decision.