InteractionEarly Phase 1NCT06693960
Evaluating the Pharmacokinetics of Oregano and Potential Oregano-drug Interactions Using a Drug Cocktail Approach
A Early Phase 1 study testing Oregano and Drug cocktail in people with Interaction, run by Washington State University at 1 site in United States.
Trial summary
The purpose of this clinical trial is to determine how the supplement oregano affects how the body metabolizes pharmaceutical drugs. Read more about this study
- Who is it for?
- Ages 18 to 64 yearsHealthy volunteers can take part
- Conditions the study is for
- Interaction
- What is being tested?
- Oregano and Drug cocktail
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 16 participants
- Where
- 1 siteUnited States
- Study dates
- 26 Sep 2024to 31 Jan 2027
- Phase
- Early Phase 1
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 64 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Between 18-64 years old and healthy
- Not taking any medications (prescription and non-prescription) or dietary/herbal supplements that can interfere with study drug pharmacokinetics
- Willing to abstain from consuming dietary/herbal supplements and citrus juices for several weeks
- Willing to abstain from cannabis/marijuana, hemp, and THC- and CBD-containing products for several weeks
- Willing to abstain from consuming caffeinated beverages or other caffeine-containing products the evening before and the morning of the first day of each study arm
- Willing to abstain from consuming any alcoholic beverages for at least 1 day prior to any study day and during the study day
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- Willing to use a secondary method of birth control that does not include the introduction or discontinuance of hormonal-based birth control (such as abstinence, copper IUD, or condoms). Specifically, regardless of the use hormonal-based birth control, a non-hormonal method should be used for the duration of the study and for three weeks following cessation of participation.
- Willing to abstain from consuming oregano (as a food additive or otherwise) for the duration of the study
- Geographically located within a 40-mile radius of Spokane and have the time to participate
Who cannot join
- Under 18 or over 64 years old
- Taking medications or dietary/herbal supplements that can interfere with study drug pharmacokinetics
- Have a major illness
- Taking medication/supplements for a mineral deficiency
- History of intolerance or allergy to oregano or any of the cocktail drugs (caffeine, dextromethorphan, losartan, midazolam, and omeprazole)
- Use of cannabis/marijuana, hemp, and CBD- and/or THC-containing products within the last month
Show all 10Show fewer
- Currently using drugs or illicit substances for recreational purposes
- Pregnant or nursing
- Geographically located outside the 40-mile radius of Spokane and do not have the time to participate
- Cannot read and speak English
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
Washington State University College of Pharmacy and Pharmaceutical Sciences
Spokane, Washington, 99202
Mary F Paine, RPh, PhD, 509-358-7759, mary.paine@wsu.edu
Mary F Paine, RPh, PhD
About this study
The purpose of this clinical trial is to determine how the supplement oregano affects how the body metabolizes pharmaceutical drugs.
Read the detailed description
Oregano (Origanum vulgare) is a flowering plant native to Europe. The fresh or dried leaves are commonly used as a cooking herb. Oregano oil extracts are also marketed as herbal supplements. O. vulgare ranked as the number 12 top-selling herbal supplement in the natural channel in 2022. Oregano supplements are consumed for myriad purported medicinal properties, including antimicrobial, antioxidant, and anti-inflammatory effects. Oregano contains multiple types of compounds, including phenols, terpenes, and terpenoids. Recent compelling in vitro data showed that an extract of O. vulgare activated the human pregnane X receptor (PXR) and aryl hydrocarbon receptor (AhR), which regulate the expression and activity of the prominent drug metabolizing enzymes cytochrome P450 (CYP) 3A4 and CYP1A2, respectively. PXR also regulates the expression and activity of several other CYPs (e.g., CYP2C9, CYP2C19), as well as transporters (e.g., the efflux transporter P-glycoprotein (P-gp)). The extent of activation of both receptors by O. vulgare rivaled that of St. John's wort, a well-known herbal supplement that induces CYP and P-gp activity in human participants. These investigators next evaluated the effects of O. vulgare on CYP3A4 and CYP1A2 activity in human hepatocytes. Again, the extent of induction by O. vulgare rivaled that of St. John's wort. Collectively, these observations suggest that oregano supplements could precipitate numerous interactions with pharmaceutical drugs.
The primary objective of the proposed study is to evaluate the potential for a well-characterized O. vulgare product to precipitate pharmacokinetic interactions with a "cocktail" of oral drugs that are substrates for multiple CYPs. The investigators and others have shown this validated cocktail (caffeine, dextromethorphan, losartan, midazolam, and omeprazole) to be safe to administer to healthy adult participants. The secondary objective is to determine the pharmacokinetics of the oregano supplement, which to date have not been rigorously characterized in humans. Results will be used to help inform healthcare practitioners and consumers about the safe use of this increasingly popular herbal supplement when consumed with certain pharmaceutical drugs.
- Conditions
- Interaction
- Being tested
- Oregano, Drug cocktail
- Keywords
- pharmacokinetics, drug interaction, natural products, oregano, cytochrome P450, cocktail
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
OreganoDietary supplement
Oil of oregano administered as a softgel (180 mg).
Drug cocktailDrug
Oral drug cocktail consisting of caffeine (100 mg), dextromethorphan (30 mg), losartan (25 mg), midazolam syrup (2 mg), and omeprazole (20 mg).
| Study group | Role | What they receive |
|---|---|---|
| Arm 1: oregano alone | Experimental | 6 participants will be administered 180 mg of a well-characterized oregano product. Blood will be drawn via an indwelling venous catheter immediately before and at 0.25, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, and 24 hours after administration of oregano. Urine will be collected in multiple jugs for 24 hours. Receives: Dietary Supplement: Oregano |
| Arm 2: drug cocktail alone | Experimental | 16 participants, which may or may not include any number of the original 6 from Arm 1, will be administered an oral drug cocktail consisting of caffeine (100 mg), dextromethorphan (30 mg), losartan (25 mg), midazolam syrup (2 mg), and omeprazole (20 mg). Blood and urine will be collected in the same manner described in Arm 1. Receives: Drug: Drug cocktail |
| Arm 3: acute oregano + cocktail | Experimental | The same 16 participants will be administered the oregano product and the drug cocktail. Blood and urine will be collected in the same manner described in Arm 1. Receives: Dietary Supplement: Oregano; Drug: Drug cocktail |
| Arm 4: chronic oregano + cocktail | Experimental | The same 16 participants will self-administer the oregano product at home for 5 consecutive days. On day 6, participants will return to the study setting, where the procedure described in Arm 3 will be repeated. Receives: Dietary Supplement: Oregano; Drug: Drug cocktail |
What is being measured
The primary outcome is the main question the study is designed to answer.
Midazolam Area under the plasma concentration vs. time curve (AUC) ratio
Ratio of the area under the plasma concentration vs. time curve of midazolam in the presence to absence of oregano.
Measured: 0-24 hours
Secondary outcomes (14)
Caffeine AUC ratio
Area under the plasma concentration vs. time curve of caffeine in the presence to absence of oregano.
Measured: 0-24 hours
Caffeine maximum plasma concentration (Cmax) ratio
Ratio of the maximum plasma concentration of caffeine in the presence to absence of oregano.
Measured: 0-24 hours
Caffeine half-life ratio
Ratio of the half-life of caffeine in the presence to absence of oregano.
Measured: 0-24 hours
Dextromethorphan AUC ratio
Area under the plasma concentration vs. time curve of dextromethorphan in the presence to absence of oregano.
Measured: 0-24 hours
Dextromethorphan Cmax ratio
Ratio of the maximum plasma concentration of dextromethorphan in the presence to absence of oregano.
Measured: 0-24 hours
Dextromethorphan half-life ratio
Ratio of the half-life of dextromethorphan in the presence to absence of oregano.
Measured: 0-24 hours
Losartan AUC ratio
Ratio of the area under the plasma concentration vs. time curve of losartan in the presence to absence of oregano.
Measured: 0-24 hours
Losartan Cmax ratio
Ratio of the maximum plasma concentration of losartan in the presence to absence of oregano.
Measured: 0-24 hours
Losartan half-life ratio
Ratio of the half-life of losartan in the presence to absence of oregano.
Measured: 0-24 hours
Midazolam Cmax ratio
Ratio of the maximum plasma concentration of midazolam in the presence to absence of oregano.
Measured: 0-24 hours
Midazolam half-life ratio
Ratio of the half-life of midazolam in the presence to absence of oregano.
Measured: 0-24 hours
Omeprazole AUC ratio
Area under the plasma concentration vs. time curve of omeprazole in the presence to absence of oregano.
Measured: 0-24 hours
Omeprazole Cmax ratio
Ratio of the maximum plasma concentration of omeprazole in the presence to absence of oregano.
Measured: 0-24 hours
Omeprazole half-life ratio
Ratio of the half-life of omeprazole in the presence to absence of oregano.
Measured: 0-24 hours
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted19 Nov 2024
- Study start26 Sep 2024
- Primary completion15 Dec 2026 (estimated)
- Study completion31 Jan 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for InteractionStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Early Phase 1
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Enrolment
- 16 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Washington State University
- Sponsor type
- University, hospital or other
- Collaborators
- Office of Dietary Supplements (ODS), National Center for Complementary and Integrative Health (NCCIH)
- Responsible party
- Principal investigator, Mary Paine, Washington State University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06693960
- Sponsor's protocol ID
- 20296
- Other IDs
- U54AT008909
- Status last verified
- Jun 2026
- First submitted
- 14 Nov 2024
- Last updated
- 4 Jun 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: IPD used in the results publication
Study at a glance
From the registry record, last updated by the sponsor on 4 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Evaluating the Pharmacokinetics of Oregano and Potential Oregano-drug Interactions Using a Drug Cocktail Approach
- ClinicalTrials.gov ID
- NCT06693960
- Acronym / sponsor ID
- 20296
- Conditions
- Interaction
- Keywords
- pharmacokinetics, drug interaction, natural products, oregano, cytochrome P450, cocktail
- Phase
- Early Phase 1
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 16 participants (estimated)
- Lead sponsor
- Washington State UniversityUniversity, hospital or other
- Collaborators
- Office of Dietary Supplements (ODS), National Center for Complementary and Integrative Health (NCCIH)
- Study start
- 26 Sep 2024 (actual)
- Primary completion
- 15 Dec 2026 (estimated)
- Study completion
- 31 Jan 2027 (estimated)
- First posted
- 19 Nov 2024 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The purpose of this clinical trial is to determine how the supplement oregano affects how the body metabolizes pharmaceutical drugs.
Detailed description
Oregano (Origanum vulgare) is a flowering plant native to Europe. The fresh or dried leaves are commonly used as a cooking herb. Oregano oil extracts are also marketed as herbal supplements. O. vulgare ranked as the number 12 top-selling herbal supplement in the natural channel in 2022. Oregano supplements are consumed for myriad purported medicinal properties, including antimicrobial, antioxidant, and anti-inflammatory effects. Oregano contains multiple types of compounds, including phenols, terpenes, and terpenoids. Recent compelling in vitro data showed that an extract of O. vulgare activated the human pregnane X receptor (PXR) and aryl hydrocarbon receptor (AhR), which regulate the expression and activity of the prominent drug metabolizing enzymes cytochrome P450 (CYP) 3A4 and CYP1A2, respectively. PXR also regulates the expression and activity of several other CYPs (e.g., CYP2C9, CYP2C19), as well as transporters (e.g., the efflux transporter P-glycoprotein (P-gp)). The extent of activation of both receptors by O. vulgare rivaled that of St. John's wort, a well-known herbal supplement that induces CYP and P-gp activity in human participants. These investigators next evaluated the effects of O. vulgare on CYP3A4 and CYP1A2 activity in human hepatocytes. Again, the extent of induction by O. vulgare rivaled that of St. John's wort. Collectively, these observations suggest that oregano supplements could precipitate numerous interactions with pharmaceutical drugs.
The primary objective of the proposed study is to evaluate the potential for a well-characterized O. vulgare product to precipitate pharmacokinetic interactions with a "cocktail" of oral drugs that are substrates for multiple CYPs. The investigators and others have shown this validated cocktail (caffeine, dextromethorphan, losartan, midazolam, and omeprazole) to be safe to administer to healthy adult participants. The secondary objective is to determine the pharmacokinetics of the oregano supplement, which to date have not been rigorously characterized in humans. Results will be used to help inform healthcare practitioners and consumers about the safe use of this increasingly popular herbal supplement when consumed with certain pharmaceutical drugs.
Study design
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 4
| Arm | Type | Receives |
|---|---|---|
| Arm 1: oregano alone | Experimental | Dietary Supplement: Oregano6 participants will be administered 180 mg of a well-characterized oregano product. Blood will be drawn via an indwelling venous catheter immediately before and at 0.25, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, and 24 hours after administration of oregano. Urine will be collected in multiple jugs for 24 hours. |
| Arm 2: drug cocktail alone | Experimental | Drug: Drug cocktail16 participants, which may or may not include any number of the original 6 from Arm 1, will be administered an oral drug cocktail consisting of caffeine (100 mg), dextromethorphan (30 mg), losartan (25 mg), midazolam syrup (2 mg), and omeprazole (20 mg). Blood and urine will be collected in the same manner described in Arm 1. |
| Arm 3: acute oregano + cocktail | Experimental | Dietary Supplement: Oregano, Drug: Drug cocktailThe same 16 participants will be administered the oregano product and the drug cocktail. Blood and urine will be collected in the same manner described in Arm 1. |
| Arm 4: chronic oregano + cocktail | Experimental | Dietary Supplement: Oregano, Drug: Drug cocktailThe same 16 participants will self-administer the oregano product at home for 5 consecutive days. On day 6, participants will return to the study setting, where the procedure described in Arm 3 will be repeated. |
Who may qualify
- Ages
- 18 to 64 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (9 listed)
- Between 18-64 years old and healthy
- Not taking any medications (prescription and non-prescription) or dietary/herbal supplements that can interfere with study drug pharmacokinetics
- Willing to abstain from consuming dietary/herbal supplements and citrus juices for several weeks
- Willing to abstain from cannabis/marijuana, hemp, and THC- and CBD-containing products for several weeks
- Willing to abstain from consuming caffeinated beverages or other caffeine-containing products the evening before and the morning of the first day of each study arm
Key exclusion criteria (10 listed)
- Under 18 or over 64 years old
- Taking medications or dietary/herbal supplements that can interfere with study drug pharmacokinetics
- Have a major illness
- Taking medication/supplements for a mineral deficiency
- History of intolerance or allergy to oregano or any of the cocktail drugs (caffeine, dextromethorphan, losartan, midazolam, and omeprazole)
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| OreganoOil of oregano administered as a softgel (180 mg). | Dietary supplement | Arm 1: oregano alone, Arm 3: acute oregano + cocktail, Arm 4: chronic oregano + cocktail |
| Drug cocktailOral drug cocktail consisting of caffeine (100 mg), dextromethorphan (30 mg), losartan (25 mg), midazolam syrup (2 mg), and omeprazole (20 mg). | Drug | Arm 2: drug cocktail alone, Arm 3: acute oregano + cocktail, Arm 4: chronic oregano + cocktail |
Primary outcome
Midazolam Area under the plasma concentration vs. time curve (AUC) ratio
Time frame: 0-24 hours
Ratio of the area under the plasma concentration vs. time curve of midazolam in the presence to absence of oregano.
14 secondary outcomes
Caffeine AUC ratio
Time frame: 0-24 hours
Caffeine maximum plasma concentration (Cmax) ratio
Time frame: 0-24 hours
Caffeine half-life ratio
Time frame: 0-24 hours
Dextromethorphan AUC ratio
Time frame: 0-24 hours
Dextromethorphan Cmax ratio
Time frame: 0-24 hours
Dextromethorphan half-life ratio
Time frame: 0-24 hours
Losartan AUC ratio
Time frame: 0-24 hours
Losartan Cmax ratio
Time frame: 0-24 hours
Losartan half-life ratio
Time frame: 0-24 hours
Midazolam Cmax ratio
Time frame: 0-24 hours
Midazolam half-life ratio
Time frame: 0-24 hours
Omeprazole AUC ratio
Time frame: 0-24 hours
Omeprazole Cmax ratio
Time frame: 0-24 hours
Omeprazole half-life ratio
Time frame: 0-24 hours
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 4 Jun 2026.
- Individual participant dataSharing planned: Yes. IPD used in the results publication
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Early Phase 1 study testing Oregano and Drug cocktail in people with Interaction, run by Washington State University at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 9 inclusion and 10 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 4 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Early Phase 1 (sometimes called Phase 0) studies give a very small amount of a treatment to a few people, mainly to see how the body handles it.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Mary F Paine, RPh, PhD (509-358-7759, mary.paine@wsu.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Midazolam Area under the plasma concentration vs. time curve (AUC) ratio (time frame: 0-24 hours). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 4 Jun 2026.