ObesityPhase 2NCT04621929
Phentermine/Topiramate for Uric Acid Stones
A Phase 2 study testing Phentermine / Topiramate Oral Product and Citrate Salts, Allopurinol, Diet in people with Obesity and Uric Acid Stones, run by University of Florida at 1 site in United States.
Trial summary
The investigator proposes an 18 month, feasibility pilot study, randomizing obese and diabetic individuals with pure uric acid nephrolithiasis (UAN) or mixed calcium oxalate (CO) UAN to either phentermine/topiramate or a pragmatic control group who will remain on their standard medication regimen (citrate salts… Read more about this study
- Who is it for?
- Ages 18 to 75 years
- Conditions the study is for
- Obesity, Uric Acid Stones, Type 2 Diabetes Mellitus in Obese
- What is being tested?
- Phentermine / Topiramate Oral Product and Citrate Salts, Allopurinol, Diet
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 19 participants
- Where
- 1 siteUnited States
- Study dates
- 31 Mar 2021to 14 Nov 2024
- Phase
- Phase 2
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
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 75 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- have recurrent pure uric acid nephrolithiasis (UAN) or mixed calcium oxalate (CO)/UAN. Recurrent stone disease is defined as at least two spontaneous kidney stone passages, two previous kidney stone procedures, or one previous stone passage and one previous procedure. Pure UAN is defined as at least one previous stone analysis demonstrating 100% uric acid mineral content. Mixed COUAN will be defined as at least one previous stone analysis with any mix of uric acid ≥80% and ≤20% calcium oxalate. If participant has more than one stone analysis, the most recent will be considered the current stone type.
- have obesity, defined as BMI > 30 kg/m2.
- have type 2 diabetes mellitus or pre-diabetes, defined as previously diagnosed by laboratory testing (hemoglobin A1c, fasting plasma glucose, or oral glucose tolerance test) or as demonstrated by use of anti-hyperglycemic medications or insulin.
- have at least one 24-hour urine study off medications demonstrating urine pH < 5.8 or a study 24-hr urine demonstrating urine pH < 5.8
Who cannot join
- contraindications to topiramate, including: recurrent major depression, current substantial depressive symptoms, uncontrolled depression by PHQ 9 score >= 10, history of suicidal ideation or behavior with intent to act (versus exclude those with depression); current pregnancy or attempting to conceive; pre-existing chronic kidney disease with eGFR < 60 at time of enrollment; active cancer or active treatment for cancer (chemotherapy, radiation); and non-ambulatory.
- contraindications to phentermine, including: unstable cardiovascular disease defined as decompensated heart failure, unstable angina, atrial fibrillation, uncontrolled blood pressure (>160 systolic), hyperthyroidism; monoamine oxidase inhibitor use; current history of drug or alcohol abuse.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Phentermine/tOpiramate to eND Obesity and Uric Acid Stones Trial (POuND OUT)
The investigator proposes an 18 month, feasibility pilot study, randomizing obese and diabetic individuals with pure uric acid nephrolithiasis (UAN) or mixed calcium oxalate (CO) UAN to either phentermine/topiramate or a pragmatic control group who will remain on their standard medication regimen (citrate salts, allopurinol, diet, etc.).
Read the detailed description
Mounting evidence indicates that obesity, diabetes mellitus, and kidney stones are inter-connected diseases, particularly uric acid nephrolithiasis (UAN) with or without components of calcium oxalate (CO). Obese or overweight diabetics have a six-fold increased risk to develop UAN/COUAN due to the inability to properly add buffer (ammonium) to urine. Of the FDA approved drugs in the weight loss market, the combination medication phentermine/ topiramate is the most effective and has a unique side effect of alkalinizing the urine (making it less acidic). The hypothesize of this project is that treatment of obese, diabetic patients with phentermine/topiramate will reduce the incidence of UAN/COUAN by 1) direct urinary alkalinization and 2) weight loss. Weight loss will indirectly improve urinary buffering ability through improvement in insulin sensitivity and will decrease renal oxidative stress. The investigative team proposes an 18 month, feasibility pilot study, randomizing 30 obese and diabetic individuals with UAN/COUAN to either phentermine/topiramate (n=20) or a pragmatic control group (n=10) who would remain on standard medication regimen (citrate salts, allopurinol, diet, etc).
- Being tested
- Phentermine / Topiramate Oral Product, Citrate Salts, Allopurinol, Diet
- Medical subject headings
- Obesity, Glucose Intolerance
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Phentermine / Topiramate Oral ProductDrug
Also called Duromine, Adipex-P, Lomaira, Suprenza
All participants in the experimental group will receive oral generic tablet phentermine (18.75 or 37.5 mg dose) and topiramate (daily 100 mg or 150 mg dose)
Citrate Salts, Allopurinol, DietCombination product
Control participants will complete initial visit requirements and study enrollment and will be maintained on their current therapy.
| Study group | Role | What they receive |
|---|---|---|
| Allocated to intervention/treatment | Experimental | Daily phentermine/topiramate x 18 months Receives: Drug: Phentermine / Topiramate Oral Product |
| Allocated to pragmatic control | Active comparator | Remain on their current regimen Receives: Combination Product: Citrate Salts, Allopurinol, Diet |
What is being measured
The primary outcome is the main question the study is designed to answer.
Kidney Stone Size (mm^3) Determined by Non-contrast CAT Scan
Stone perimeter within each cut of CT image was outlined using semiautomated volume tool (region of interest pen tool, CT software "Visage Imaging") and tallied to calculate stone volume (mm^3) for each individual stone and recorded from right and left kidney from all study participants at baseline CT and at end of study CT (18 months)
Measured: Baseline, 18 months
Secondary outcomes (6)
Weight (kg)
total weight (baseline and end of study)
Measured: Baseline, 18 months
Urinary pH Parameters
urine pH (baseline and end of study). The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic.
Measured: Baseline, 18 months
%Hemoglobin A1c
%A1c (baseline and end of study)
Measured: Baseline, 18 months
Urinary Citrate Parameters
urinary citrate (baseline and end of study)
Measured: Baseline, 18 months
Urinary Calcium Parameters
urinary calcium (baseline and end of study)
Measured: Baseline, 18 months
Urinary Uric Acid Supersaturation (SS)
Urinary uric acid SS (before and end of study). Urinary Uric Acid Supersaturation (SS) is not measured in a specific unit, as it is a ratio. Result below 1: The urine is undersaturated, meaning that crystals are more likely to dissolve than form. Result equal to 1: The urine is in equilibrium with uric acid, so crystals will not grow or shrink. Result above 1: The urine is supersaturated, and the risk for crystals to form and grow is increased. A higher value indicates a greater risk.
Measured: Baseline, 18 months
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted9 Nov 2020
- Study start31 Mar 2021
- Primary completion14 Nov 2024
- Study completion14 Nov 2024
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Other trials for ObesityStudies of the same condition, open and under way.
- More trials run by University of FloridaThe sponsor's other registered studies.
- 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 2
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- 2:1 ratio block site of 6
- Masking
- None (open label)
- Enrolment
- 19 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Florida
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Benjamin Canales, MD, Principal investigator, University of Florida
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04621929
- Sponsor's protocol ID
- IRB202001895-A-N
- Other IDs
- 1R21DK122317-01A1
- Status last verified
- Nov 2024
- First submitted
- 3 Nov 2020
- Last updated
- 15 Jun 2026
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 15 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Phentermine/tOpiramate to eND Obesity and Uric Acid Stones Trial (POuND OUT)
- ClinicalTrials.gov ID
- NCT04621929
- Acronym / sponsor ID
- IRB202001895-A-N
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 19 participants (actual)
- Lead sponsor
- University of FloridaUniversity, hospital or other
- Collaborators
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
- Study start
- 31 Mar 2021 (actual)
- Primary completion
- 14 Nov 2024 (actual)
- Study completion
- 14 Nov 2024 (actual)
- First posted
- 9 Nov 2020 (actual)
- Results
- Posted 30 Jan 2026
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The investigator proposes an 18 month, feasibility pilot study, randomizing obese and diabetic individuals with pure uric acid nephrolithiasis (UAN) or mixed calcium oxalate (CO) UAN to either phentermine/topiramate or a pragmatic control group who will remain on their standard medication regimen (citrate salts, allopurinol, diet, etc.).
Detailed description
Mounting evidence indicates that obesity, diabetes mellitus, and kidney stones are inter-connected diseases, particularly uric acid nephrolithiasis (UAN) with or without components of calcium oxalate (CO). Obese or overweight diabetics have a six-fold increased risk to develop UAN/COUAN due to the inability to properly add buffer (ammonium) to urine. Of the FDA approved drugs in the weight loss market, the combination medication phentermine/ topiramate is the most effective and has a unique side effect of alkalinizing the urine (making it less acidic). The hypothesize of this project is that treatment of obese, diabetic patients with phentermine/topiramate will reduce the incidence of UAN/COUAN by 1) direct urinary alkalinization and 2) weight loss. Weight loss will indirectly improve urinary buffering ability through improvement in insulin sensitivity and will decrease renal oxidative stress. The investigative team proposes an 18 month, feasibility pilot study, randomizing 30 obese and diabetic individuals with UAN/COUAN to either phentermine/topiramate (n=20) or a pragmatic control group (n=10) who would remain on standard medication regimen (citrate salts, allopurinol, diet, etc).
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
- Model description
- 2:1 ratio block site of 6
| Arm | Type | Receives |
|---|---|---|
| Allocated to intervention/treatment | Experimental | Drug: Phentermine / Topiramate Oral ProductDaily phentermine/topiramate x 18 months |
| Allocated to pragmatic control | Active comparator | Combination Product: Citrate Salts, Allopurinol, DietRemain on their current regimen |
Who may qualify
- Ages
- 18 to 75 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (4 listed)
- have recurrent pure uric acid nephrolithiasis (UAN) or mixed calcium oxalate (CO)/UAN. Recurrent stone disease is defined as at least two spontaneous kidney stone passages, two previous kidney stone procedures, or one previous stone passage and one previous procedure. Pure UAN is defined as at least one previous stone analysis demonstrating 100% uric acid mineral content. Mixed COUAN will be defined as at least one previous stone analysis with any mix of uric acid ≥80% and ≤20% calcium oxalate. If participant has more than one stone analysis, the most recent will be considered the current stone type.
- have obesity, defined as BMI > 30 kg/m2.
- have type 2 diabetes mellitus or pre-diabetes, defined as previously diagnosed by laboratory testing (hemoglobin A1c, fasting plasma glucose, or oral glucose tolerance test) or as demonstrated by use of anti-hyperglycemic medications or insulin.
- have at least one 24-hour urine study off medications demonstrating urine pH < 5.8 or a study 24-hr urine demonstrating urine pH < 5.8
Key exclusion criteria (2 listed)
- contraindications to topiramate, including: recurrent major depression, current substantial depressive symptoms, uncontrolled depression by PHQ 9 score >= 10, history of suicidal ideation or behavior with intent to act (versus exclude those with depression); current pregnancy or attempting to conceive; pre-existing chronic kidney disease with eGFR < 60 at time of enrollment; active cancer or active treatment for cancer (chemotherapy, radiation); and non-ambulatory.
- contraindications to phentermine, including: unstable cardiovascular disease defined as decompensated heart failure, unstable angina, atrial fibrillation, uncontrolled blood pressure (>160 systolic), hyperthyroidism; monoamine oxidase inhibitor use; current history of drug or alcohol abuse.
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 |
|---|---|---|
| Phentermine / Topiramate Oral ProductAlso: Duromine, Adipex-P, Lomaira, SuprenzaAll participants in the experimental group will receive oral generic tablet phentermine (18.75 or 37.5 mg dose) and topiramate (daily 100 mg or 150 mg dose) | Drug | Allocated to intervention/treatment |
| Citrate Salts, Allopurinol, DietControl participants will complete initial visit requirements and study enrollment and will be maintained on their current therapy. | Combination product | Allocated to pragmatic control |
Primary outcome
Kidney Stone Size (mm^3) Determined by Non-contrast CAT Scan
Time frame: Baseline, 18 months
Stone perimeter within each cut of CT image was outlined using semiautomated volume tool (region of interest pen tool, CT software "Visage Imaging") and tallied to calculate stone volume (mm^3) for each individual stone and recorded from right and left kidney from all study participants at baseline CT and at end of study CT (18 months)
6 secondary outcomes
Weight (kg)
Time frame: Baseline, 18 months
Urinary pH Parameters
Time frame: Baseline, 18 months
%Hemoglobin A1c
Time frame: Baseline, 18 months
Urinary Citrate Parameters
Time frame: Baseline, 18 months
Urinary Calcium Parameters
Time frame: Baseline, 18 months
Urinary Uric Acid Supersaturation (SS)
Time frame: Baseline, 18 months
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 15 Jun 2026.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- 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.
Benjamin Canales, MD principal investigator
University of Florida
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing Phentermine / Topiramate Oral Product and Citrate Salts, Allopurinol, Diet in people with Obesity and Uric Acid Stones, run by University of Florida 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 4 inclusion and 2 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 15 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?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
Yes. Results are posted in the registry (first posted 30 Jan 2026). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
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?
Kidney Stone Size (mm^3) Determined by Non-contrast CAT Scan (time frame: Baseline, 18 months). 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 15 Jun 2026.