A Phase 1 interventional study of Sildenafil citrate vaginal suppository in Dysmenorrhea, Menstrual Pain and Endometriosis, sponsored by Kevin Hellman. Not yet recruiting at 1 site in United States. Open to female participants aged 18 Years to 35 Years. Per ClinicalTrials.gov, last updated 2026-09-25.
Sponsored by Kevin Hellman · Phase 1, Interventional, and Basic science
This open-label, non-randomized mechanistic study will evaluate whether a single 100 mg vaginal sildenafil citrate suppository reduces uterine hypercontractility during menstruation in adults with moderate-to-severe dysmenorrhea. Ten participants will each receive one open-label dose during a single menstrual treatment visit and will serve as their own control: 6 participants with primary dysmenorrhea and no evidence of pelvic pathology, plus a separately analyzed exploratory subset of 4 participants, 2 with known endometriosis and 2 with known uterine fibroids. Uterine contractility will be measured with cine magnetic resonance imaging (MRI) before dosing and approximately 4 hours after dosing. Additional objectives are to evaluate acute menstrual pain over the 4-hour observation window, to document systemic exposure using sparse plasma sampling at approximately 2 and 4 hours after dosing, and to assess short-term safety and local tolerability.
Dysmenorrhea is believed to be driven in part by excessive uterine contractility. Sildenafil, a phosphodiesterase-5 inhibitor, may reduce myometrial hypercontractility through enhanced nitric oxide-cGMP signaling. Prior vaginal sildenafil data suggested acute pain relief, but mechanism and systemic exposure were not well characterized.
This study is a mechanistic biomarker investigation in which uterine contractility measured by cine MRI serves as a functional pharmacodynamic marker of PDE5 inhibition. Participants complete a screening visit (medical history, vital signs, 12-lead ECG, screening laboratory tests, MRI safety screening, questionnaires) and a gynecologic examination visit before dosing. When a participant is menstruating and reporting cramping pain of at least 5 on a 0 to 10 scale, she attends a single treatment visit of approximately 6 hours. At that visit she undergoes a pre-dose cine MRI, self-administers a single 100 mg vaginal sildenafil citrate suppository, and undergoes a repeat MRI at approximately 4 hours after dosing. No MRI is obtained at the 2-hour timepoint. Pain ratings on a 100-mm visual analog scale, vital signs, adverse event assessment, and venous blood samples for plasma sildenafil and its N-desmethyl metabolite are obtained at approximately 2 and 4 hours after dosing. In a prespecified exploratory subset of 2 participants, an additional plasma sample is obtained at approximately 24 hours after dosing at a brief return blood-draw visit. Menstrual effluent is collected during the visit. Electronic side-effect questionnaires are sent at 6 and 24 hours after dosing, and a second gynecologic examination visit occurs within approximately one month after the treatment visit.
There is no placebo and no comparator group. The primary analysis is the within-participant change from pre-dose baseline in the number of uterine contractions during a standardized 10-minute cine MRI acquisition. The planned population of 10 participants comprises 6 participants with primary dysmenorrhea and no evidence of pelvic pathology, plus a separately analyzed exploratory subset of 4 participants (2 with known endometriosis and 2 with known uterine fibroids).
Plasma sampling in this study is deliberately sparse because participants are in acute menstrual pain. Formal pharmacokinetic parameters such as Cmax, Tmax, area under the concentration-time curve, and terminal half-life will not be derived from this study; the samples are intended to document whether measurable systemic exposure occurs after vaginal administration and to relate exposure to hemodynamic and adverse event outcomes.
430 studies on the registry are indexed under Dysmenorrhea; 107 are open to participants now.
This study's planned enrollment of 10 is below the median of 62 across 363 interventional studies indexed under Dysmenorrhea.
Browse Dysmenorrhea studies →This is the only study on the registry with Kevin Hellman as lead sponsor.
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The criteria were revised on the registry on Sep 25, 2026. See what changed
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
CYP3A is a group of enzymes, mainly CYP3A4, in the liver and gut that break down many medicines. Some medicines, supplements and foods (grapefruit, St John’s wort) slow them down or speed them up, which changes how much of a study drug stays in the body.
Studies list them so they can be avoided or switched; bring a list of everything you take, including supplements.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
CYP3A (CYP3A4) inhibitors and inducers
CYP3A is a group of enzymes, mainly CYP3A4, in the liver and gut that break down many medicines. Some medicines, supplements and foods (grapefruit, St John’s wort) slow them down or speed them up, which changes how much of a study drug stays in the body.
Studies list them so they can be avoided or switched; bring a list of everything you take, including supplements.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Platelets
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hemoglobin (Hb)
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
All participants receive a single open-label 100 mg vaginal sildenafil citrate suppository during one menstrual treatment visit, self-administered after the pre-dose MRI. Uterine contractility, pain ratings, vital signs, and plasma concentrations are assessed before and after dosing within the same visit.
Drug: Sildenafil citrate vaginal suppository
A single 100 mg vaginal sildenafil citrate suppository, compounded in an emulsifying MBK base, is self-administered once during the menstrual treatment visit. Treatment is open-label and known to participants and study staff.
Also known as: Vaginal sildenafil 100 mg
Change from baseline in number of uterine contractions during a 10-minute cine MRI acquisition
Uterine contractility will be quantified as the number of uterine contractions observed during a standardized 10-minute cine MRI acquisition. The primary analysis is the within-participant change from pre-dose baseline after a single open-label 100 mg vaginal dose of sildenafil citrate. A decrease indicates reduced uterine contractility.
Time frame: Baseline (pre-dose) and approximately 4 hours after dosing
Menstrual pain intensity AUC from 0 to 4 hours measured by 100-mm visual analog scale
Menstrual pain intensity will be recorded using a 100-mm visual analog scale, where 0 indicates no pain and 100 indicates worst imaginable pain. Ratings are obtained pre-dose and at approximately 2 and 4 hours after dosing. Area under the curve from 0 to 4 hours will be calculated using the trapezoidal method; lower values indicate lower overall pain burden.
Time frame: Baseline (pre-dose) through approximately 4 hours after dosing
Plasma sildenafil concentration
Venous plasma sildenafil concentration will be measured to document whether measurable systemic exposure occurs after vaginal administration. Sampling is sparse by design; formal pharmacokinetic parameters such as Cmax, Tmax, AUC, and terminal half-life will not be derived in this study.
Time frame: Approximately 2 and 4 hours after dosing in all participants; additionally approximately 24 hours after dosing in an exploratory subset of 2 participants
Plasma N-desmethyl sildenafil concentration
Venous plasma concentration of the active N-desmethyl metabolite of sildenafil will be measured to document whether measurable systemic exposure occurs after vaginal administration. Sampling is sparse by design; formal pharmacokinetic parameters such as Cmax, Tmax, AUC, and terminal half-life will not be derived in this study.
Time frame: Approximately 2 and 4 hours after dosing in all participants; additionally approximately 24 hours after dosing in an exploratory subset of 2 participants
Change from baseline in systolic blood pressure
Hemodynamic tolerability will be assessed by change from pre-dose baseline in systolic blood pressure measured during the treatment visit.
Time frame: Baseline (pre-dose), approximately 2 hours after dosing, and approximately 4 hours after dosing
Change from baseline in diastolic blood pressure
Hemodynamic tolerability will be assessed by change from pre-dose baseline in diastolic blood pressure measured during the treatment visit.
Time frame: Baseline (pre-dose), approximately 2 hours after dosing, and approximately 4 hours after dosing
Change from baseline in heart rate
Hemodynamic tolerability will be assessed by change from pre-dose baseline in heart rate measured during the treatment visit.
Time frame: Baseline (pre-dose), approximately 2 hours after dosing, and approximately 4 hours after dosing
Number of participants with treatment-emergent adverse events, including local vaginal tolerability findings
Adverse events and symptoms potentially related to PDE5 inhibition or vaginal administration, including headache, flushing, dizziness or lightheadedness, visual disturbances, palpitations, syncope, vaginal irritation, local discomfort, abnormal discharge, and acute changes in bleeding, will be collected during the treatment visit, by electronic side-effect questionnaires at 6 and 24 hours after dosing, and at the post-treatment gynecologic examination visit.
Time frame: From study drug administration through the post-treatment gynecologic examination, up to approximately 1 month after dosing
Correlation between change in uterine contraction count and change in menstrual pain intensity
An exploratory mechanistic analysis will evaluate whether attenuation of uterine hypercontractility is associated with reduction in menstrual pain intensity during the acute observation window. The measure is the Spearman rank correlation coefficient between the within-participant change from pre-dose baseline in uterine contraction count on cine MRI and the within-participant change from pre-dose baseline in menstrual pain intensity on a 100-mm visual analog scale, both assessed at approximately 4 hours after dosing. Both changes are calculated as the post-dose value minus the pre-dose value, so a reduction is a negative change. The coefficient ranges from -1 to 1; a positive value indicates that larger reductions in contraction count accompany larger reductions in pain.
Time frame: Baseline (pre-dose) and approximately 4 hours after dosing
Plan to share: Yes — De-identified individual participant data underlying the results reported in this study will be shared. This includes: Participant-level demographic and baseline characteristics (e.g., age, menstrual history, eligibility variables) Visit-level and timepoint-level indicators for the open-label dosing visit Primary outcome data: number of uterine contractions during the standardized 10-minute cine MRI acquisition at baseline and approximately 4 hours after dosing Plasma sildenafil and N-desmethyl sildenafil concentrations Adverse event and safety monitoring data Derived variables and analysis datasets used to generate reported results Data will be shared in a de-identified format consistent with applicable privacy regulations.
Supporting information: Study protocol, Statistical analysis plan, Informed consent form, Analytic code
Time frame: Data will be available beginning approximately 6 months after publication of the primary results and will remain available indefinitely.
Access criteria: Access to de-identified individual participant data and supporting documents will be provided to qualified researchers upon reasonable request and approval of a research proposal by the study investigators. A data use agreement will be required. Data will be shared via a secure, controlled-access mechanism.
Data sharing details ↗ · www.cureperiodpain.org
No publications or documents are linked to this record.
Start is estimated for Oct 2026; primary completion for Jun 2027, 8 months later.
Since we started tracking on Sep 25, 2026, the dates moved once, on Sep 25, 2026: start May 2026 → Oct 2026, primary completion May 2027 → Jun 2027 and completion Oct 2027 → Jul 2027.
Earlier changes are on the record history on ClinicalTrials.gov ↗
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is not yet recruiting, as verified in Sep 2026. You cannot join it, but the record below documents what was studied.
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