A Phase 2 interventional study of Phentermine and Placebo in Childhood Obesity, sponsored by Russell McCulloh, MD. Recruiting at 8 sites in United States. Open to participants aged 12 Years to 17 Years. Per ClinicalTrials.gov, last updated 2026-10-07.
Sponsored by Russell McCulloh, MD · Phase 2, Interventional, and Treatment
PhITT is a Phase IIb, multicenter, randomized, double-blind, placebo-controlled clinical trial evaluating the efficacy and safety of phentermine (16 mg daily) in adolescents aged 12 to \<18 years with obesity. Conducted across approximately 10 sites within the IDeA States Pediatric Clinical Trials Network (ISPCTN), the study aims to enroll up to 240 participants and then randomize up to 198 who meet eligibility criteria, randomized in a 2:1 ratio to phentermine or placebo over a 52-week treatment period, followed by a 2-week withdrawal assessment.
1,129 studies on the registry are indexed under Pediatric Obesity; 187 are open to participants now.
This study's planned enrollment of 240 is above the median of 100 across 870 interventional studies indexed under Pediatric Obesity.
Browse Pediatric Obesity studies →This is the only study on the registry with Russell McCulloh, MD as lead sponsor.
Counted across the registry records on this site, refreshed daily.
Inclusion criteria* include, but are not limited to:
Exclusion criteria* include, but are not limited to:
to phentermine in adults such as:
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.
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.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
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.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
How quickly the kidneys clear creatinine, a waste product, from the blood. A study may estimate it from a blood test with age, weight and sex (often by the Cockcroft–Gault formula), or measure it using blood and urine collected over a set time. Given in mL/min; higher is better.
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.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
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.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
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.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ALT and AST (liver enzymes)
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Creatinine clearance (CrCl)
How quickly the kidneys clear creatinine, a waste product, from the blood. A study may estimate it from a blood test with age, weight and sex (often by the Cockcroft–Gault formula), or measure it using blood and urine collected over a set time. Given in mL/min; higher is better.
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.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants in this arm will receive phentermine 16 mg daily, administered as two 8 mg tablets taken orally once
Drug: Phentermine
Participants in this arm will receive placebo tablets that are visually identical to the phentermine tablets but contain no active pharmaceutical ingredient. The placebo will be taken orally once daily in the morning for 52 weeks. All participants will also receive lifestyle education handouts at each study visit. This arm serves as the control group for evaluating the efficacy and safety of phentermine in adolescents with obesity.
Drug: Placebo
Phentermine 16 mg administered orally once daily in the morning for 52 weeks. The dose is provided as two 8 mg tablets. Participants also receive lifestyle education handouts at each study visit. The intervention is designed to evaluate the efficacy and safety of phentermine for weight loss in adolescents with obesity.
Placebo tablets that are visually identical to phentermine tablets but contain no active pharmaceutical ingredient. Administered orally once daily in the morning for 52 weeks. Participants also receive lifestyle education handouts at each study visit. This control arm is used to evaluate the efficacy and safety of phentermine in adolescents with obesity.
Percent Change in BMI from Baseline at Week 52
Change in body mass index (BMI) expressed as a percentage of baseline BMI at week 52.
Time frame: 52 weeks
Number of Treatment-Emergent Adverse Events (TEAEs)
Count of TEAEs deemed probably or definitely related to study drug, including common side effects
Time frame: 52 weeks
Number of Treatment-Emergent Adverse Events of Special Interest (TEAESIs)
Count of TEAESIs deemed probably or definitely related to study drug, including tachycardia, hypertension, depression, suicidality, and withdrawal symptoms
Time frame: 52 weeks
Changes in Cardiometabolic Risk Factor Waist Circumference
Change in waist circumference from baseline
Time frame: 52 weeks
Changes in Cardiometabolic Risk Factor Blood Pressure
Change blood pressure from baseline
Time frame: 52 weeks
Changes in Cardiometabolic Risk Factor Glucose
Change in glucose from baseline
Time frame: 52 weeks
Changes in Cardiometabolic Risk Factor Lipids
Change in lipids from baseline
Time frame: 52 weeks
Changes in Cardiometabolic Risk Factor Hemoglobin A1C
Change in hemoglobin A1C from baseline
Time frame: 52 weeks
Plan to share: Yes — De-identified individual-level data including baseline characteristics, outcome measures and adverse events.
Supporting information: Study protocol, Statistical analysis plan, Informed consent form
No publications or documents are linked to this record.
Started Jun 2026 (actual). Primary completion is estimated for Jan 2028, 19 months after the start.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
Contact study teamGet 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: Phentermine