Endometriosis-associated pain and CBD suppositories
OMG Pharma is sponsoring a pharmacokinetic and open-label pilot study evaluating cannabidiol (CBD) suppositories for pelvic pain in adults with confirmed endometriosis — conducted with experienced research partners under appropriate human research ethics oversight.
The programme is designed to characterise absorption and physiological effects, assess feasibility and acceptability, and generate exploratory evidence on pain, quality of life and symptom burden over one menstrual cycle.
Background & rationale
Endometriosis is a chronic condition in which tissue similar to the uterine lining grows outside the uterus, often causing pelvic pain, dysmenorrhoea and reduced quality of life. Many people living with endometriosis continue to experience significant symptom burden despite available treatments.
CBD suppositories represent a novel cannabinoid-based formulation designed to provide localised, sustained release of therapeutic compounds directly to the pelvic region. This route of administration may offer distinct pharmacokinetic advantages over oral or systemic delivery, including enhanced bioavailability, reduced first-pass metabolism, and potentially superior tissue penetration to target sites of pain generation.
Women experience endometriosis
people worldwide experience endometriosis
Study overview
CBD suppositories for endometriosis-associated pain: a pharmacokinetic and open-label pilot study comprises three integrated sub-studies:
- A pharmacokinetic assessment to characterise the absorption, distribution and preliminary clinical effects of CBD rectal suppositories (75 mg) in individuals with confirmed endometriosis.
- Transabdominal Doppler ultrasound (TADU) to assess any effect of CBD rectal suppositories on uterine artery perfusion, including pulsatility index (PI) and resistance index (RI), conducted alongside the pharmacokinetic visit.
- An open-label intervention phase to assess feasibility and indicative subjective clinical responses on pain and quality of life, measured using the Endometriosis Health Profile 30 (EHP-30) and the Most Impactful Symptom of Endometriosis Questionnaire (MSIE-Q), in line with minimum dataset recommendations for endometriosis research.
CBD per suppository dose
Approximate duration per
participant
Integrated sub-studies: pharmacokinetics, ultrasound and open-label pilot
Study objectives
Primary objectives
- Characterise pharmacokinetic profiles of CBD suppositories following rectal administration, including absorption kinetics, peak plasma concentrations (Cmax), time to peak concentration (Tmax), area under the concentration-time curve (AUC) and elimination half-life.
- Evaluate feasibility and acceptability of OMG CBD suppositories for pelvic pain management through patient-reported adherence and satisfaction measures.
- Assess physiological effects on uterine artery perfusion through TADU imaging and explore correlations between plasma cannabinoid levels and uterine PI/RI.
Secondary objectives
- Investigate impact on endometriosis-specific quality of life, most impactful symptom, work attendance and rescue analgesic medication requirements.
- Explore effectiveness of once or twice daily 75 mg CBD suppositories in reducing menstrual and non-menstrual pain severity over one complete menstrual cycle.
- Assess the safety profile of OMG CBD suppositories.
Study design
The programme comprises two phases:
Phase 1
Baseline assessment including Doppler ultrasound and pharmacokinetic characterisation following rectal administration of a single 75 mg CBD suppository during an 8–10 hour on-site visit at NICM.
Phase 2
Participants self-administer CBD suppositories daily across one menstrual cycle, with optional twice-daily dosing if pain is severe. Route of administration (rectal or vaginal) is participant choice and may be changed at any time.
Study population: Adults aged 21 years and older with confirmed endometriosis (via laparoscopic surgery or imaging), clinically significant dysmenorrhoea, and currently using a form of menstrual suppression with regular menstrual or withdrawal bleeding.
Who can participate
Key inclusion criteria
- Aged 21 years or older
- Confirmed endometriosis diagnosis via laparoscopy or expert imaging (TVUS or MRI)
- Moderate-to-severe dysmenorrhoea requiring medical attention and/or analgesia
- Regular menstrual cycle (21–35 days) through hormonal regulation (e.g. oral contraceptive with scheduled withdrawal bleeds)
- Cannabis-naive or willing to abstain from cannabis and other cannabinoid medications for at least 4 weeks before entry and throughout the study
- Able to attend scheduled visits, including an 8-hour pharmacokinetic sampling day
- English comprehension sufficient for questionnaires and informed consent
Key exclusion criteria
- Currently pregnant, breastfeeding or planning pregnancy during the study
- Unwilling to use appropriate contraception if sexually active with pregnancy potential
- Known allergy or hypersensitivity to cannabinoids or formulation components
- Clinically significant abnormal liver or kidney function at screening, or hormonal suppression that does not allow regular withdrawal bleeding
- Any condition that, in the investigator’s opinion, would compromise safety or data integrity
What participants can expect
Screening and baseline (Week 0)
Eligible participants complete a screening call, provide informed consent, and undergo baseline blood tests including liver and kidney function, high-sensitivity C-reactive protein (hs-CRP) and pregnancy testing where applicable.
Baseline monitoring (Weeks 1–4)
From the first day of menstruation or withdrawal bleeding, participants complete a daily pain diary for 30 days, recording menstrual status, pelvic pain intensity (worst and average, 0–10 NRS), pain location and rescue medication use. Baseline EHP-30 and MSIE-Q questionnaires are also collected.
Phase 1 visit (~Weeks 2–3)
After fasting for 2 hours, participants attend NICM for an 8–10 hour visit. Procedures include vital signs, urine pregnancy test (if required), baseline TADU, supervised self-administration of one 75 mg CBD suppository, serial blood sampling (baseline through 8 hours on-site, plus 24-hour sample at external pathology) and repeat TADU at 1, 2, 4, 6 and 8 hours. A ~40-day supply of study product is dispensed at visit end.
Phase 2 treatment (~Weeks 4–9)
From day 1 of the next menstrual period, participants use one 75 mg suppository each evening, with an optional second dose if pain is severe (10–12 hours apart). Daily diaries continue until day 5 of the following cycle (~25–35 days), logging pain, medication use, dose count, route and adverse events. End-of- treatment EHP-30, MSIE-Q and satisfaction questionnaires are completed.
End of study (Week ~10)
Safety blood tests (liver, kidney, hs-CRP) are repeated at an external pathology laboratory within one week of trial completion.
Outcomes measured
Primary outcomes
- Pharmacokinetic parameters for CBD and key metabolites (Cmax, Tmax, AUC, half-life, clearance and volume of distribution)
- Changes in uterine artery perfusion indices (PI, RI) and correlations with plasma cannabinoid levels
- Proportion achieving ≥30% and ≥50% reduction in non-menstrual pain scores, and changes in NRS scores for menstrual and non-menstrual pain
Secondary outcomes
- EHP-30 total and subscale scores; MSIE-Q changes
- Rescue analgesic usage, including opioid vs non-opioid medication
- Treatment satisfaction, acceptability and route preference
- Safety: adverse events, laboratory parameters and treatment discontinuation rate
Study timeline
Week 0
Screening, informed consent, baseline blood tests
Weeks 1–4
Baseline monitoring: daily pain diary, EHP-30 and MSIE-Q
Weeks 2–3
Phase 1: pharmacokinetic and TADU assessment visit at NICM
Weeks 4–9
Phase 2: open-label treatment across one menstrual cycle
Week ~10
End-of-study safety blood tests
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Research collaboration
Meet our research partners
OMG Pharma’s endometriosis programme is delivered with experienced academic investigators at NICM Health Research Institute, Western Sydney University.
Lead Researcher · NICM Health Research Institute
Associate Professor Mike Armour, PhD
Mike Armour is Associate Professor in Reproductive Health and Director of Research at the NICM Health Research Institute, Western Sydney University. He is a world- leading expert in period pain, endometriosis and chronic pelvic pain, with a special interest in medicinal cannabis.
He has led four prior clinical studies on medicinal cannabis, published more than 140 peer-reviewed articles, and contributed to Australian clinical guidelines and international evidence resources. Mike leads OMG Pharma’s endometriosis research collaboration at NICM.
References
- World Health Organization (WHO) Endometriosis Fact Sheet, 2023
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Frequently asked questions
What is this study investigating?
The study evaluates OMG CBD suppositories (75 mg) in adults with confirmed endometriosis. It combines pharmacokinetic characterisation, ultrasound assessment of uterine artery perfusion, and an open-label treatment phase exploring pain, quality of life and symptom outcomes.
Who is eligible to take part?
Adults aged 21+ with confirmed endometriosis, moderate-to-severe dysmenorrhoea, and regular withdrawal bleeding on hormonal suppression may be eligible. Full inclusion and exclusion criteria are assessed at screening. Participants must be willing to abstain from cannabis and other cannabinoids during the study.
How long does participation take?
The programme runs for approximately 9–10 weeks per participant, including screening, a 30-day baseline monitoring period, an 8–10 hour pharmacokinetic visit, one menstrual cycle of daily treatment, and end-of-study safety blood tests.
Can participants choose how the suppository is administered?
During Phase 2, participants may choose rectal or vaginal administration based on preference, and may change route at any time. Phase 1 pharmacokinetic assessment uses rectal administration under supervision to standardise absorption sampling.
What questionnaires and diaries are used?
Participants complete the EHP-30 (Endometriosis Health Profile), MSIE-Q (Most Impactful Symptom of Endometriosis Questionnaire), a daily pain diary, and a treatment satisfaction questionnaire. These tools capture pain intensity, symptom burden, quality of life and product acceptability.
How is participant safety monitored?
Safety monitoring includes adverse event reporting throughout the study, vital signs at the pharmacokinetic visit, and repeat liver function, kidney function and hs-CRP testing at screening and end of trial. Investigators assess causality and manage any events requiring medical attention.
How can I register interest or ask a question?
For general enquiries about OMG Pharma research, use our contact form or email info@ozmedicann.com. Recruitment updates will be shared when appropriate.