An interventional study of Yohimbine and Consumption of a defined potato-rich meal in Pharmacokinetic Study in Healthy Volunteers, sponsored by University Medicine Greifswald. Not yet recruiting at 1 site in Germany. Open to participants aged 18 Years to 40 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-14.
Sponsored by University Medicine Greifswald · Not applicable, Interventional, and Basic science
This study investigates the evaluation of solanidine as an exogenous biomarker to phenotype CYP2D6-activity in humans. Participants will be classified by their CYP2D6 genotype into poor metabolizers (PM), low intermediate metabolizers (LIM), extensive metabolizers (EM) and ultra-rapid metabolizers (UM), forming four distinct study arms:
Arm 1) Poor Metabolizers (PM) n=10 Arm 2) Low Intermediate Metabolizers (LIM) n=5 Arm 3) Extensive Metabolizers (EM) n=10 Arm 4) Ultra-rapid Metabolizers (UM) n=5
Participants will be given a standardized potato-rich meal, serving as the natural source of solanidine, and will be phenotyped for CYP2D6 activity with a single oral microdose of the probe drug yohimbine.
The objectives of the study are as follows:
The study follows an open-label, controlled, parallel-cohort design with four study arms based on CYP2D6 genotype. The study consists of two parts: a Yohimbine and a Potato Part.
Yohimbine Part:
Participants will receive a single oral microdose of 50 μg of yohimbine, administered in a fasted state as 2 x 1 tablets of Yohimbinum hydrochloricum D4® (Deutsche Homöopathie Union, Karlsruhe, Germany, containing 25 μg per tablet). A total of 6 blood samples will be collected at defined time points (baseline; 10; 20; 30; 60; 120 min). At each time point, 5 mL of blood will be drawn for plasma separation to determine yohimbine and the primary metabolite 11-OH-yohimbine. The blood sampling protocol is based on the findings of the YOKI-1 study (protocol number: IPHA-2025-011, Greifswald Ethics Committee Registration number BB 069/25). At baseline, an additional blood sample will be collected for a random determination of solanidine and its metabolites. During the 2.5-hour stay in the CRU, participants will be asked to stay in bed.
Potato Part:
Between the Potato and the Yohimbine Part, a period of 4 weeks in any order is acceptable. The Potato Part is divided into two sequential phases: Phase 1 and Phase 2, both featuring supervised meal ingestion at the clincal research unit. During the three days before each Potato Phase and up to 60 hours afterward, no potato products should be eaten. Otherwise, ad libitum food intake is permitted beginning six hours after the potato-rich meal. Blood samples will be analyzed for solanidine, its CYP2D6-dependent metabolites, and its parent molecules α-solanine and α-chaconine in both Potato Phases. Both Potato Phases must be separated by at least one week.
Phase 1 (0-12 hours postprandial):
An initial baseline blood sample will be collected prior to the ingestion of the potato-rich meal. Participants will receive the potato-rich meal at 8 a.m., and a total of 7 blood samples will be collected at defined time points (baseline, 2, 4, 6, 8, 10, and 12 h).Upon successful completion of the 12-hour blood draw, participants will be discharged from the CRU.
Phase 2 (12-60 hours postprandial):
On a separate scheduled study day, participants will report to the CRU at 7:30 p.m. A baseline blood sample will be collected prior to meal ingestion. Participants will then ingest an identical, defined potato-rich meal at 8:00 p.m. Following meal consumption, participants are permitted to go home for the night. The next morning, starting at 7:30 a.m., blood sampling collections will begin at the designated time points. A total of ten blood samples will be collected at defined time points (baseline, 12, 14, 16, 18, 20, 22, 24 h, 36 h in the next morning and at 60 h in the morning thereafter).
University Medicine Greifswald is the lead sponsor of 152 studies on the registry; 22 are open to participants now.
Counted across the registry records on this site, refreshed daily.
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.
Poor Metabolizer (PM, Gen-Score 0):
homozygous or compound heterozygous for CYP2D6 *3, CYP2D6 *4, CYP2D6*5, CYP2D6 *6
Low Intermediate Metabolizer (LIM, Gen-Score 0,25 or 0,5):
Homozygous or compound heterozygous for CYP2D6 *9, *10, *41 or compound heterozygous with one allele of CYP2D6 *3, CYP2D6 *4, CYP2D6*5, or CYP2D6*6 and one allele of CYP2D6 *17 (0,5) or CYP2D6 *9, *10, or *41 (0,25)
Extensive Metabolizer (EM, Gene-Score 2):
homozygous or compound heterozygous for CYP2D6 *1, CYP2D6 *2, CYP2D6*35
Ultrarapid Metabolizer (UM, Gen-Score ≥ 3):
homozygous or compound heterozygous for CYP2D6 *1, CYP2D6 *2, CYP2D6*35 with at least one allele duplicated or multiplied
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.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
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 yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
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.
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.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
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.
Bilirubin
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ULN (upper limit of normal)
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
QT and QTc
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECG (electrocardiogram)
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
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.
Participants in this arm are classified as poor metabolizers (PM, Gene-Score 0) based on their CYP2D6 genotype. Poor metabolizers are homozygous or compound heterozygous for CYP2D6 \*3, CYP2D6 \*4, CYP2D6 \*5, CYP2D6 \*6. Participants were selected to achieve best matching between arms according to age, BMI, alcohol consumption and smoking.
Dietary Supplement: Yohimbine · Other: Consumption of a defined potato-rich meal
Low intermediae metabolizers (LIM, Gene-Score 0,25 or 0,5) are homozygous or compound heterozygous for CYP2D6 \*9, \*10, \*41 or compound heterozygous with one allele of CYP2D6 \*3, CYP2D6 \*4, CYP2D6\*5, or CYP2D6 \*6 and one allele of CYP2D6 \*17 (0,5) or CYP2D6 \*9, \*10, or \*41 (0,25). Participants were selected to achieve best matching between arms according to age, BMI, alcohol consumption and smoking.
Dietary Supplement: Yohimbine · Other: Consumption of a defined potato-rich meal
Extensive Metabolizer (EM, Gene-Score 2) are homozygous or compound heterozygous for CYP2D6 \*1, CYP2D6 \*2, CYP2D6\*35. Participants were selected to achieve best matching between arms according to age, BMI, alcohol consumption and smoking.
Dietary Supplement: Yohimbine · Other: Consumption of a defined potato-rich meal
Ultrarapid Metabolizer (UM, Gen-Score ≥ 3) are homozygous or compound heterozygous for CYP2D6 \*1, CYP2D6 \*2, CYP2D6\*35 with at least one allele duplicated or multiplied. Participants were selected to achieve best matching between arms according to age, BMI, alcohol consumption and smoking.
Dietary Supplement: Yohimbine · Other: Consumption of a defined potato-rich meal
A single oral dose of 50 µg yohimbine, administered as 2 x 1 tablets of Yohimbinum hydrochloricum D4® will be administered as drinking solution with 240mL of water under overnight fasting conditions. A total of 6 blood samples will be collected at defined time points (baseline; 10; 20; 30; 60; 120 min). At each time point, 5 mL of blood will be drawn for plasma separation to determine yohimbine and the primary metabolite 11-OH-yohimbine.
Potato Intervention (2 phases): Diet restriction: No potato products 3 days before and until 60h after each meal. Ad libitum food intake is allowed from 6h post-meal. Blood will be analyzed for solanidine, its metabolites and its parent molecules α-solanine, and α-chaconine. Phase 1 (0-12h postprandial): Baseline blood draw at 8:00 AM, followed by supervised ingestion of a potato-rich meal. A total of 7 blood samples will be collected (baseline, 2, 4, 6, 8, 10, 12h) before discharge from the CRU. Phase 2 (12-60h postprandial): Baseline blood draw at 7:30 PM, identical meal ingestion at 8:00 PM. Participants can go home afterwards and return to the CRU the next morning at 8:00 AM for their 12 hour post meal blood draw. A total of 10 blood samples will be collected (baseline, 12, 14, 16, 18, 20, 22, 24h, 36h next morning, 60h subsequent morning).
Also known as: potato-rich meal, potato
Metabolic ratio of SSDA/solanidine
This study determines the sensitivity of the metabolic ratio of SSDA/solanidine and the metabolic ratio of m414/solanidine to correctly identify the CYP2D6 metabolizer status. Each MR will be considered separately in order to identify the most suitable one. As we will recruit individuals from the lowest and highest level of CYP2D6 activity, we will test the sensitivity independently for the prediction of the lowest activity level (PM + LIM) and the highest activity level (EM + UM). The "true" CYP2D6 metabolizer status will be determined by the combination of the CYP2D6 genotype and the yohimbine-determined phenotype in recruited individuals. Those individuals with a perfect match of genotype and phenotype are considered the controls to which the solanidine results are then compared as the ratio of phenotype predicted (by solandine MR)/ phenotype determined (by genotyping + yohimbine-phenotyping)
Time frame: From enrollment to 60 hours after eating the potato-rich meal.
AUC for solanidine, SSDA, m414, α-solanine and α-chaconine
Plasma concentrations expressed as area under the curve (AUC) will be determined for solanidine, its CYP2D6-dependent metabolites SSDA and m414, and its parent molecules α-solanine and α-chaconine for each metabolizer status cohort (PM, LIM, EM, UM).
Time frame: 60 hours
Cmax for solanidine, SSDA, m414, α-solanine and α-chaconine
The maximum concentration (Cmax) will be determined for solanidine, its CYP2D6-dependent metabolites SSDA and m414, and its parent molecules α-solanine and α-chaconine for each metabolizer status cohort (PM, LIM, EM, UM).
Time frame: 60 hours
Tmax for solanidine, SSDA, m414, α-solanine and α-chaconine
Time to maximum concentration (tmax) of solanidine, its CYP2D6-dependent metabolites SSDA and m414, and its parent molecules α-solanine and α-chaconine will be determined for each metabolizer status cohort (PM, LIM, EM, UM).
Time frame: 60 hours
Plan to share: No
No publications or documents are linked to this record.
Start is estimated for Sep 2026; primary completion for Sep 2027, 12 months later.
How these figures are worked out, and which studies are left out of them.
This study is not yet recruiting, as verified in Sep 2026. You cannot join it, but the record below documents what was studied.
Get an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
Studies of the drug tested here: Yohimbine
University Medicine Greifswald →