Pharmacokinetic Study in Healthy VolunteersYOKI-1NCT06939608
Kinetics of Yohimbine in Humans to Explore Sex and CYP2D6 Genotype Interactions
A study testing Yohimbine and ¹³C₃-caffeine in people with Pharmacokinetic Study in Healthy Volunteers, run by University Medicine Greifswald at 1 site in Germany.
Trial summary
This study investigates the pharmacokinetics of yohimbine in women and men aged 18 to 40 years to explore sex-specific differences in CYP2D6-dependent drug metabolism. Participants will be classified by their CYP2D6 genotype into extensive metabolizers (EM) and poor metabolizers (PM), forming four distinct study arms… Read more about this study
- Who is it for?
- Ages 18 to 40 yearsHealthy volunteers can take part
- Conditions the study is for
- Pharmacokinetic Study in Healthy Volunteers
- What is being tested?
- Yohimbine and ¹³C₃-caffeine
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 36 participants
- Where
- 1 siteGermany
- Study dates
- 28 Apr 2025to 10 Oct 2025
- Phase
- Interventional
- Are there results?
- None posted in the registry
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 40 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- individuals of both biological sexes, assigned as women or men at birth
- age: ≥ 18 and ≤ 40 years
- possesses the ability to understand the study purpose and design
- contractually capable and provides signed informed consent form
- in good general health or with mild and/or well-managed conditions such as allergies, asthma, hypertension or orthopedic diseases
- taking no more than three chronic medications
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- individuals classified as either extensive metabolizers (EM) or poor metabolizers (PM) based on their CYP2D6 genotype:
- Extensive Metabolizers (EM):
- homozygous for CYP2D6 1,CYP2D6 2, CYP2D6 35, or heterozygous combination of any of these alleles
- Poor Metabolizers (PM):
- homozygous for CYP2D6 3, CYP2D6 4, CYP2D6 5, CYP2D6 6, or heterozygous combination of any of these alleles
Who cannot join
- BMI > 30 kg/m2 and < 18 kg/m2
- body weight < 48 kg
- women: known pregnancy or lactation period; positive urine pregnancy test at screening or kinetic visit
- men: hemoglobin < 13 g/dl (8,07 mmol/l) women: hemoglobin < 12 g/dl (7,45 mmol/l)
- elevated liver function tests (1 or more of ALAT, ASAT, yGT, Bilirubin > 2x ULN)
- reduced renal function (eGFRMDRD < 60 mL/min/1,7 m2)
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- QTcF > 450 ms in screening ECG
- current or recent psychiatric disorders requiring treatment including depression, bipolar disorder, schizophrenia, psychosis or severe anxiety disorders
- drug dependency at the time of visit
- use of recreational drugs more than twice a week
- any known hypersensitivity or allergic reactions to yohimbine or caffeine
- history of severe hypersensitivity reactions and/or anaphylaxis
- poor venous conditions that make it impossible to place a peripheral venous catheter and regularly draw blood through it
- intake of drugs interfering with CYP2D6 and/or CYP1A2 during the past seven days p) intake of yohimbine within 48 hours and caffeine within 16 hours prior to study participation q) engagement in extreme physical activity within 48 hours prior to study participation
Trial locations and contacts
1 site in 1 country.
Germany1 site
University Medicine Greifswald, Institute of Pharmacology
Greifswald, Mecklenburg-Vorpommern, 17489
About this study
Official title: Kinetics of Yohimbine in Humans to Explore Sex and CYP2D6 Genotype Interactions - YOKI-1 Study
This study investigates the pharmacokinetics of yohimbine in women and men aged 18 to 40 years to explore sex-specific differences in CYP2D6-dependent drug metabolism. Participants will be classified by their CYP2D6 genotype into extensive metabolizers (EM) and poor metabolizers (PM), forming four distinct study arms:
Arm 1) Women, Poor Metabolizers (PM) n=13 Arm 2) Women, Extensive Metabolizers (EM) n=5 Arm 3) Men, Poor Metabolizers (PM) n=13 Arm 4) Men, Extensive Metabolizers (EM) n=5
Read more
Each study arm will receive a single oral dose of 50 µg yohimbine (2 x 1 tablets, 25 µg per tablet) and 25 mg of ¹³C₃-caffeine co-administered as a drinking solution.
The purpose of this study is:
- To characterize the pharmacokinetics of yohimbine following a single oral dose in women and men across different CYP2D6 phenotypes.
- To evaluate yohimbine's suitability as a reliable probe for assessing CYP2D6 activity.
- To investigate potential interactions between CYP2D6 and CYP1A2, as well as interindividual variability in CYP1A2-dependent caffeine metabolism.
Read the detailed description
The study is designed as an open-label, single-dose protocol with four study arms based on sex and CYP2D6 genotype. A single oral dose of yohimbine and ¹³C₃-caffeine will be administered with 240 ml of still water under overnight fasting conditions.
A total of 19 blood samples will be collected at defined time points (baseline; 10; 20; 30; 40; 50; 60; 70; 80; 90; 100; 110 min; 2; 3; 4; 6; 8; 10; 24 h). At each time point, 4.9 mL of blood will be drawn for plasma separation to determine yohimbine, the primary metabolite 11-OH-yohimbine and 13C₃-caffeine with associated CYP1A2 dependent metabolites. One additional blood sample (EDTA tube) for potential future genetic analysis, will be collected together with the baseline kinetic samples.
For each participant, a total of approximately 98 mL of blood will be collected during the kinetic visits and an additional 12 mL during the screening visit.
Following the administration of yohimbine and 13C3-caffeine, participants will consume 200 mL of sparkling water every hour to stimulate gastrointestinal peristalsis facilitate substance transport. Two hours post-administration, participants may have a cup of tea or coffee, while a standardized meal will be served four hours after dosing.
Urine samples will be collected over 24 hours in three intervals (0-4 h, 5-10 h, 11-24 h). Blood pressure and heart rate monitoring will be conducted during the initial four hours and participants will remain in the Clinical Research Unit of the Institute of Pharmacology for the first 10 hours post-administration. At 24 hours post-dosing, participants will return to the Clinical Research Unit for the final scheduled blood collection and to provide their last urine sample (11-24 h).
- Being tested
- Yohimbine, ¹³C₃-caffeine
- Keywords
- sex-specific differences, pharmacokinetics, yohimbine, CYP2D6, genetic polymorphisms, drug metabolism, CYP1A2, ¹³C₃-caffeine
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
YohimbineDietary supplement
A single oral dose of 50 µg yohimbine, administered as 2 x 1 tablets of Yohimbinum hydrochloricum D4® will be co-administered with 25 mg of ¹³C₃-caffeine as drinking solution with 240mL of still water under overnight fasting conditions. A total of 19 blood samples will be collected at defined time points (baseline; 10; 20; 30; 40; 50; 60; 70; 80; 90; 100; 110 min; 2; 3; 4; 6; 8; 10; 24 h). At each time point, 4.9 mL of blood will be drawn for plasma separation to determine yohimbine, the primary metabolite 11-OH-yohimbine and ¹³C₃-caffeine with associated CYP1A2 dependent metabolites.
¹³C₃-caffeineOther
A single oral dose of 25 mg of ¹³C₃-caffeine as a drinking solution will be co-administered with yohimbine with 240 mL of still water under overnight fasting conditions. ¹³C₃-caffeine is a stable isotope-labeled standard probe for phenotyping CYP1A2 activity and assessing potential interactions between CYP2D6 and CYP1A2. Plasma concentrations of ¹³C₃-caffeine with associated CYP1A2 dependent metabolites will be measured at predefined time points, following the sampling schedule outlined for yohimbine.
| Study group | Role | What they receive |
|---|---|---|
| Women, Poor Metabolizers (PM) | Active comparator | Participants in this arm are women, as identified by their sex assigned at birth, classified as poor metabolizers (PM) based on their CYP2D6 genotype. Poor metabolizers are homozygous for CYP2D6 *3, *4, *5, *6 or carry heterozygous combinations of these alleles. Participants were selected to achieve best matching between arms according to age, BMI, alcohol consumption and smoking. Receives: Dietary Supplement: Yohimbine; Other: ¹³C₃-caffeine |
| Women, Extensive Metabolizers (EM) | Active comparator | Participants in this arm are women, as identified by their sex assigned at birth, classified as extensive metabolizers (EM) based on their CYP2D6 genotype. Extensive metabolizers are homozygous for CYP2D6 *1, *2, *35 or carry heterozygous combinations of these alleles. Participants were selected to achieve best matching between arms according to age, BMI, alcohol consumption and smoking. Receives: Dietary Supplement: Yohimbine; Other: ¹³C₃-caffeine |
| Men, Poor Metabolizers (PM) | Active comparator | Participants in this arm are men, as identified by their sex assigned at birth, classified as poor metabolizers (PM) based on their CYP2D6 genotype. Poor metabolizers are homozygous for CYP2D6 *3, *4, *5, *6 or carry heterozygous combinations of these alleles. Participants were selected to achieve best matching between arms according to age, BMI, alcohol consumption and smoking. Receives: Dietary Supplement: Yohimbine; Other: ¹³C₃-caffeine |
| Men, Extensive Metabolizers (EM) | Active comparator | Participants in this arm are men, as identified by their sex assigned at birth, classified as extensive metabolizers (EM) based on their CYP2D6 genotype. Extensive metabolizers are homozygous for CYP2D6 *1, *2, *35 or carry heterozygous combinations of these alleles. Participants were selected to achieve best matching between arms according to age, BMI, alcohol consumption and smoking. Receives: Dietary Supplement: Yohimbine; Other: ¹³C₃-caffeine |
What is being measured
The primary outcome is the main question the study is designed to answer.
Yohimbine plasma concentration expressed as area under the curve (AUC₀-₂₄h) - arm 1 vs. arm 3
Difference in plasma concentrations of yohimbine expressed as area under the curve (AUC₀-₂₄h) between women classified as CYP2D6 poor metabolizers (PM) (arm 1) and men classified as CYP2D6 poor metabolizers (PM) (arm 3).
Measured: 24 hours
Yohimbine plasma concentration expressed as area under the curve (AUC₀-₂₄h) - arm 1 vs. arm 2
Difference in plasma concentrations of yohimbine expressed as area under the curve (AUC₀-₂₄h) between women classified as CYP2D6 poor metabolizers (PM) (arm 1) and women classified as CYP2D6 extensive metabolizers (EM) (arm 2).
Measured: 24 hours
Yohimbine plasma concentration expressed as area under the curve (AUC₀-₂₄h) - arm 3 vs. arm 4
Difference in plasma concentrations of yohimbine expressed as area under the curve (AUC₀-₂₄h) between men classified as CYP2D6 poor metabolizers (PM) (arm 3) and men classified as CYP2D6 extensive metabolizers (EM) (arm 4).
Measured: 24 hours
Secondary outcomes (5)
Cmax of yohimbine and 11-OH-yohimbine
Differences in maximum concentration (Cmax) of yohimbine and the primary metabolite 11-OH-yohimbine between CYP2D6 poor metabolizers (PM) and extensive metabolizers (EM) within the same sex (Arm 1 vs. Arm 2 and Arm 3 vs. Arm 4) and between women and men classified as PM (Arm 1 vs. Arm 3) and EM (Arm 2 vs. Arm 4).
Measured: 24 hours
tmax of yohimbine and 11-OH-yohimbine
Differences in time to maximum concentration (tmax) of yohimbine and the primary metabolite 11-OH-yohimbine between CYP2D6 poor metabolizers (PM) and extensive metabolizers (EM) within the same sex (Arm 1 vs. Arm 2 and Arm 3 vs. Arm 4) and between women and men classified as PM (Arm 1 vs. Arm 3) and EM (Arm 2 vs. Arm 4).
Measured: 24 hours
Clearance of yohimbine and 11-OH-yohimbine
Differences in total and renal clearance of yohimbine and the primary metabolite 11-OH-yohimbine between CYP2D6 poor metabolizers (PM) and extensive metabolizers (EM) within the same sex (Arm 1 vs. Arm 2 and Arm 3 vs. Arm 4) and between women and men classified as PM (Arm 1 vs. Arm 3) and EM (Arm 2 vs. Arm 4).
Measured: 24 hours
Apparent volume of distribution of yohimbine and 11-OH-yohimbine
Differences in apparent volume of distribution of yohimbine and the primary metabolite 11-OH-yohimbine between CYP2D6 poor metabolizers (PM) and extensive metabolizers (EM) within the same sex (Arm 1 vs. Arm 2 and Arm 3 vs. Arm 4) and between women and men classified as PM (Arm 1 vs. Arm 3) and EM (Arm 2 vs. Arm 4).
Measured: 24 hours
11-OH-Yohimbine plasma concentration expressed as area under the curve (AUC₀-₂₄h)
Differences in plasma concentrations of 11-OH-yohimbine expressed as area under the curve (AUC₀-₂₄h) between CYP2D6 poor metabolizers (PM) and extensive metabolizers (EM) within the same sex (Arm 1 vs. Arm 2 and Arm 3 vs. Arm 4) and between women and men classified as PM (Arm 1 vs. Arm 3) and EM (Arm 2 vs. Arm 4).
Measured: 24 hours
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted23 Apr 2025
- Study start28 Apr 2025
- Primary completion10 Oct 2025
- Study completion10 Oct 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Pharmacokinetic Study in Healthy VolunteersStudies 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
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Parallel groups
- Model description
- The study is designed as an open-label, four-arm, parallel assignment, single oral dose protocol, stratifying participants by CYP2D6 genotype (extensive vs. poor metabolizers) and biological sex (women vs. men).
- Masking
- None (open label)
- Enrolment
- 36 participants (actual)
Sponsor and investigators
- Lead sponsor
- University Medicine Greifswald
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Stefan Engeli, MD, University Medicine Greifswald
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06939608
- Sponsor's protocol ID
- IPHA-2025-011
- Acronym
- YOKI-1
- Status last verified
- Jan 2026
- First submitted
- 31 Mar 2025
- Last updated
- 21 Jan 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 21 Jan 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Kinetics of Yohimbine in Humans to Explore Sex and CYP2D6 Genotype Interactions - YOKI-1 Study
- ClinicalTrials.gov ID
- NCT06939608
- Acronym / sponsor ID
- YOKI-1 / IPHA-2025-011
- Keywords
- sex-specific differences, pharmacokinetics, yohimbine, CYP2D6, genetic polymorphisms, drug metabolism, CYP1A2, ¹³C₃-caffeine
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 36 participants (actual)
- Lead sponsor
- University Medicine GreifswaldUniversity, hospital or other
- Study start
- 28 Apr 2025 (actual)
- Primary completion
- 10 Oct 2025 (actual)
- Study completion
- 10 Oct 2025 (actual)
- First posted
- 23 Apr 2025 (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.
This study investigates the pharmacokinetics of yohimbine in women and men aged 18 to 40 years to explore sex-specific differences in CYP2D6-dependent drug metabolism. Participants will be classified by their CYP2D6 genotype into extensive metabolizers (EM) and poor metabolizers (PM), forming four distinct study arms:
Arm 1) Women, Poor Metabolizers (PM) n=13 Arm 2) Women, Extensive Metabolizers (EM) n=5 Arm 3) Men, Poor Metabolizers (PM) n=13 Arm 4) Men, Extensive Metabolizers (EM) n=5
Each study arm will receive a single oral dose of 50 µg yohimbine (2 x 1 tablets, 25 µg per tablet) and 25 mg of ¹³C₃-caffeine co-administered as a drinking solution.
The purpose of this study is:
- To characterize the pharmacokinetics of yohimbine following a single oral dose in women and men across different CYP2D6 phenotypes.
- To evaluate yohimbine's suitability as a reliable probe for assessing CYP2D6 activity.
- To investigate potential interactions between CYP2D6 and CYP1A2, as well as interindividual variability in CYP1A2-dependent caffeine metabolism.
Detailed description
The study is designed as an open-label, single-dose protocol with four study arms based on sex and CYP2D6 genotype. A single oral dose of yohimbine and ¹³C₃-caffeine will be administered with 240 ml of still water under overnight fasting conditions.
A total of 19 blood samples will be collected at defined time points (baseline; 10; 20; 30; 40; 50; 60; 70; 80; 90; 100; 110 min; 2; 3; 4; 6; 8; 10; 24 h). At each time point, 4.9 mL of blood will be drawn for plasma separation to determine yohimbine, the primary metabolite 11-OH-yohimbine and 13C₃-caffeine with associated CYP1A2 dependent metabolites. One additional blood sample (EDTA tube) for potential future genetic analysis, will be collected together with the baseline kinetic samples.
For each participant, a total of approximately 98 mL of blood will be collected during the kinetic visits and an additional 12 mL during the screening visit.
Following the administration of yohimbine and 13C3-caffeine, participants will consume 200 mL of sparkling water every hour to stimulate gastrointestinal peristalsis facilitate substance transport. Two hours post-administration, participants may have a cup of tea or coffee, while a standardized meal will be served four hours after dosing.
Urine samples will be collected over 24 hours in three intervals (0-4 h, 5-10 h, 11-24 h). Blood pressure and heart rate monitoring will be conducted during the initial four hours and participants will remain in the Clinical Research Unit of the Institute of Pharmacology for the first 10 hours post-administration. At 24 hours post-dosing, participants will return to the Clinical Research Unit for the final scheduled blood collection and to provide their last urine sample (11-24 h).
Study design
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 4
- Model description
- The study is designed as an open-label, four-arm, parallel assignment, single oral dose protocol, stratifying participants by CYP2D6 genotype (extensive vs. poor metabolizers) and biological sex (women vs. men).
| Arm | Type | Receives |
|---|---|---|
| Women, Poor Metabolizers (PM) | Active comparator | Dietary Supplement: Yohimbine, Other: ¹³C₃-caffeineParticipants in this arm are women, as identified by their sex assigned at birth, classified as poor metabolizers (PM) based on their CYP2D6 genotype. Poor metabolizers are homozygous for CYP2D6 *3, *4, *5, *6 or carry heterozygous combinations of these alleles. Participants were selected to achieve best matching between arms according to age, BMI, alcohol consumption and smoking. |
| Women, Extensive Metabolizers (EM) | Active comparator | Dietary Supplement: Yohimbine, Other: ¹³C₃-caffeineParticipants in this arm are women, as identified by their sex assigned at birth, classified as extensive metabolizers (EM) based on their CYP2D6 genotype. Extensive metabolizers are homozygous for CYP2D6 *1, *2, *35 or carry heterozygous combinations of these alleles. Participants were selected to achieve best matching between arms according to age, BMI, alcohol consumption and smoking. |
| Men, Poor Metabolizers (PM) | Active comparator | Dietary Supplement: Yohimbine, Other: ¹³C₃-caffeineParticipants in this arm are men, as identified by their sex assigned at birth, classified as poor metabolizers (PM) based on their CYP2D6 genotype. Poor metabolizers are homozygous for CYP2D6 *3, *4, *5, *6 or carry heterozygous combinations of these alleles. Participants were selected to achieve best matching between arms according to age, BMI, alcohol consumption and smoking. |
| Men, Extensive Metabolizers (EM) | Active comparator | Dietary Supplement: Yohimbine, Other: ¹³C₃-caffeineParticipants in this arm are men, as identified by their sex assigned at birth, classified as extensive metabolizers (EM) based on their CYP2D6 genotype. Extensive metabolizers are homozygous for CYP2D6 *1, *2, *35 or carry heterozygous combinations of these alleles. Participants were selected to achieve best matching between arms according to age, BMI, alcohol consumption and smoking. |
Who may qualify
- Ages
- 18 to 40 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (11 listed)
- individuals of both biological sexes, assigned as women or men at birth
- age: ≥ 18 and ≤ 40 years
- possesses the ability to understand the study purpose and design
- contractually capable and provides signed informed consent form
- in good general health or with mild and/or well-managed conditions such as allergies, asthma, hypertension or orthopedic diseases
Key exclusion criteria (14 listed)
- BMI > 30 kg/m2 and < 18 kg/m2
- body weight < 48 kg
- women: known pregnancy or lactation period; positive urine pregnancy test at screening or kinetic visit
- men: hemoglobin < 13 g/dl (8,07 mmol/l) women: hemoglobin < 12 g/dl (7,45 mmol/l)
- elevated liver function tests (1 or more of ALAT, ASAT, yGT, Bilirubin > 2x ULN)
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 |
|---|---|---|
| YohimbineA single oral dose of 50 µg yohimbine, administered as 2 x 1 tablets of Yohimbinum hydrochloricum D4® will be co-administered with 25 mg of ¹³C₃-caffeine as drinking solution with 240mL of still water under overnight fasting conditions. A total of 19 blood samples will be collected at defined time points (baseline; 10; 20; 30; 40; 50; 60; 70; 80; 90; 100; 110 min; 2; 3; 4; 6; 8; 10; 24 h). At each time point, 4.9 mL of blood will be drawn for plasma separation to determine yohimbine, the primary metabolite 11-OH-yohimbine and ¹³C₃-caffeine with associated CYP1A2 dependent metabolites. | Dietary supplement | Men, Extensive Metabolizers (EM), Men, Poor Metabolizers (PM), Women, Extensive Metabolizers (EM), Women, Poor Metabolizers (PM) |
| ¹³C₃-caffeineA single oral dose of 25 mg of ¹³C₃-caffeine as a drinking solution will be co-administered with yohimbine with 240 mL of still water under overnight fasting conditions. ¹³C₃-caffeine is a stable isotope-labeled standard probe for phenotyping CYP1A2 activity and assessing potential interactions between CYP2D6 and CYP1A2. Plasma concentrations of ¹³C₃-caffeine with associated CYP1A2 dependent metabolites will be measured at predefined time points, following the sampling schedule outlined for yohimbine. | Other | Men, Extensive Metabolizers (EM), Men, Poor Metabolizers (PM), Women, Extensive Metabolizers (EM), Women, Poor Metabolizers (PM) |
Primary outcome
Yohimbine plasma concentration expressed as area under the curve (AUC₀-₂₄h) - arm 1 vs. arm 3
Time frame: 24 hours
Difference in plasma concentrations of yohimbine expressed as area under the curve (AUC₀-₂₄h) between women classified as CYP2D6 poor metabolizers (PM) (arm 1) and men classified as CYP2D6 poor metabolizers (PM) (arm 3).
Yohimbine plasma concentration expressed as area under the curve (AUC₀-₂₄h) - arm 1 vs. arm 2
Time frame: 24 hours
Difference in plasma concentrations of yohimbine expressed as area under the curve (AUC₀-₂₄h) between women classified as CYP2D6 poor metabolizers (PM) (arm 1) and women classified as CYP2D6 extensive metabolizers (EM) (arm 2).
Yohimbine plasma concentration expressed as area under the curve (AUC₀-₂₄h) - arm 3 vs. arm 4
Time frame: 24 hours
Difference in plasma concentrations of yohimbine expressed as area under the curve (AUC₀-₂₄h) between men classified as CYP2D6 poor metabolizers (PM) (arm 3) and men classified as CYP2D6 extensive metabolizers (EM) (arm 4).
5 secondary outcomes
Cmax of yohimbine and 11-OH-yohimbine
Time frame: 24 hours
tmax of yohimbine and 11-OH-yohimbine
Time frame: 24 hours
Clearance of yohimbine and 11-OH-yohimbine
Time frame: 24 hours
Apparent volume of distribution of yohimbine and 11-OH-yohimbine
Time frame: 24 hours
11-OH-Yohimbine plasma concentration expressed as area under the curve (AUC₀-₂₄h)
Time frame: 24 hours
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 21 Jan 2026.
- Individual participant dataSharing planned: No
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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. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Yohimbine and ¹³C₃-caffeine in people with Pharmacokinetic Study in Healthy Volunteers, run by University Medicine Greifswald at 1 site in Germany.
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 11 inclusion and 14 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: finished, as of the sponsor's last update on 21 Jan 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 Germany. 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.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Yohimbine plasma concentration expressed as area under the curve (AUC₀-₂₄h) - arm 1 vs. arm 3 (time frame: 24 hours). The study lists 3 primary outcomes in all. 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 21 Jan 2026.