A Phase 4 interventional study of Phentermine 15 MG and Phentermine 30 mg in Obesity & Overweight, sponsored by OSCAR MANUEL TORRES FALCON. Completed at 1 site in Mexico. Open to participants aged 21 Years to 40 Years. Per ClinicalTrials.gov, last updated 2026-10-13.
Sponsored by OSCAR MANUEL TORRES FALCON · Phase 4, Interventional, and Treatment
This study evaluated the effects of intermittent phentermine treatment on body fat, estimated visceral adiposity, body composition, and tolerability in adults with overweight or obesity.
A total of 600 adults aged 21 to 40 years with a body mass index (BMI) between 27 and 35 kg/m² participated in a single-center, randomized, four-group clinical trial conducted at Hospital Médica Campestre in León, Guanajuato, Mexico.
Participants were assigned to lifestyle modification alone or lifestyle modification combined with phentermine at doses of 15 mg, 30 mg, or 37.5 mg daily. Phentermine was administered intermittently using a schedule of three months of treatment followed by one month without medication during a 14-month observation period.
All participants received nutritional guidance and physical activity recommendations. Body composition was assessed using bioelectrical impedance analysis and three-dimensional body scanning.
The primary outcome was the relative percentage reduction in total body fat from baseline to Month 14. Secondary outcomes included estimated visceral adiposity, waist circumference, lean body mass, body weight, BMI, medication adherence, resting heart rate, blood pressure, treatment-emergent adverse events, and treatment discontinuation.
The study aimed to evaluate the dose-response effects of intermittent phentermine on body composition and the balance between efficacy and tolerability.
This investigator-initiated, single-site, randomized, parallel-group clinical trial evaluated the efficacy and tolerability of intermittent, dose-stratified phentermine therapy combined with structured lifestyle modification.
A total of 600 adults aged 21-40 years with BMI values between 27 and 35 kg/m² were randomized in a 1:1:1:1 ratio to four groups: lifestyle-only control, phentermine 15 mg, phentermine 30 mg, or phentermine 37.5 mg, with 150 participants per group.
All participants received a structured lifestyle intervention targeting an approximate daily energy deficit of 500 kcal and 150 minutes of aerobic physical activity per week. Participants assigned to pharmacological treatment received oral phentermine hydrochloride once daily during active treatment periods. The intermittent treatment schedule consisted of three consecutive months of medication followed by one month without medication during the 14-month observation period.
Body composition was evaluated using multifrequency bioelectrical impedance analysis and three-dimensional optical body scanning. Assessments included total body fat, estimated visceral adiposity, waist circumference, lean body mass, body weight, and BMI.
The primary endpoint was the relative percentage reduction in total body fat from baseline to Month 14. Secondary endpoints included relative percentage reduction in estimated visceral adiposity, absolute change in waist circumference, change in lean body mass, body weight, BMI, medication adherence, resting heart rate, blood pressure, treatment-emergent adverse events, and treatment discontinuation.
The intervention was open label for participants and treating clinicians, while body-composition assessors and the primary statistical analyst were blinded to treatment allocation.
The study was conducted at Hospital Médica Campestre in León, Guanajuato, Mexico, under protocol 1-0029, approved by the Hospital Médica Campestre Ethics Committee.
6,570 studies on the registry are indexed under Obesity; 1,718 are open to participants now.
This study's enrollment of 600 is above the median of 77 across 5,084 interventional studies indexed under Obesity.
Browse Obesity studies →This is the only study on the registry with OSCAR MANUEL TORRES FALCON as lead sponsor.
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Exclusion Criteria:
Participants received structured lifestyle treatment targeting an energy deficit of approximately 500 kcal/day and approximately 150 minutes/week of aerobic physical activity, without phentermine administration.
Behavioral: Lifestyle Management
Participants received oral phentermine hydrochloride 15 mg once daily during active-treatment periods using a planned intermittent schedule of 3 months on treatment followed by 1 month off treatment, repeated over the 14-month observation period, in combination with structured lifestyle treatment.
Drug: Phentermine 15 MG · Behavioral: Lifestyle Management
Participants received oral phentermine hydrochloride 30 mg once daily during active-treatment periods using a planned intermittent schedule of 3 months on treatment followed by 1 month off treatment, repeated over the 14-month observation period, in combination with structured lifestyle treatment.
Drug: Phentermine 30 mg · Behavioral: Lifestyle Management
Participants received oral phentermine hydrochloride 37.5 mg once daily during active-treatment periods using a planned intermittent schedule of 3 months on treatment followed by 1 month off treatment, repeated over the 14-month observation period, in combination with structured lifestyle treatment.
Drug: Phentermine 37.5 Mg · Behavioral: Lifestyle Management
Oral phentermine hydrochloride 15 mg administered once daily during active-treatment periods using a planned intermittent schedule of 3 months on treatment followed by 1 month off treatment, repeated over the 14-month observation period, in combination with structured lifestyle treatment.
Oral phentermine hydrochloride 30 mg administered once daily during active-treatment periods using a planned intermittent schedule of 3 months on treatment followed by 1 month off treatment, repeated over the 14-month observation period, in combination with structured lifestyle treatment.
Oral phentermine hydrochloride 37.5 mg administered once daily during active-treatment periods using a planned intermittent schedule of 3 months on treatment followed by 1 month off treatment, repeated over the 14-month observation period, in combination with structured lifestyle treatment.
Structured lifestyle treatment targeting an energy deficit of approximately 500 kcal/day and approximately 150 minutes/week of aerobic physical activity.
Relative Percentage Reduction in Total Body Fat from Baseline
Relative percentage reduction in total body fat from baseline to Month 14, calculated as 100 × (baseline value - Month 14 value) / baseline value.
Time frame: Baseline through Month 14
Relative Percentage Reduction in Estimated Visceral Adiposity from Baseline
Relative percentage reduction in estimated visceral adiposity from baseline to Month 14, calculated as 100 × (baseline value - Month 14 value) / baseline value. Visceral adiposity was estimated using the study body-composition assessment protocol and was not directly measured by CT or MRI.
Time frame: Baseline and 14 months
Change in Lean Body Mass from Baseline
Change in estimated lean mass from baseline, assessed using bioelectrical impedance analysis to compare changes among the lifestyle control group and the three intermittent phentermine dose groups.
Time frame: Baseline and 14 months
Change in Body Weight from Baseline
Change in body weight from baseline, expressed as absolute weight change and percentage of initial body weight, comparing the lifestyle control group with the three intermittent phentermine dose groups.
Time frame: Baseline and 14 months
Treatment-Emergent Adverse Events.
Number and percentage of participants experiencing treatment-emergent adverse events during the study. Adverse events were assessed at scheduled visits and by spontaneous reporting and were classified according to severity and relationship to treatment.
Time frame: Baseline through Month 14
Waist Circumference
Absolute change in waist circumference from baseline to Month 14, measured in centimeters.
Time frame: Baseline to Month 14
Change in Body Mass Index from Baseline
Change in body mass index (BMI) from baseline to Month 14, calculated as body weight in kilograms divided by height in meters squared (kg/m²).
Time frame: Baseline to Month 14
Medication Adherence
Medication adherence during the study, assessed from planned medication exposure, medication accountability, and scheduled follow-up visits.
Time frame: Baseline through Month 14
Resting Heart Rate
Change in resting heart rate from baseline through Month 14, measured in beats per minute during scheduled study visits.
Time frame: Baseline through Month 14
Blood Pressure
Change in systolic and diastolic blood pressure from baseline through Month 14, assessed during scheduled study visits.
Time frame: Baseline through Month 14
Treatment Discontinuation
Number and percentage of participants who discontinued treatment during the study, including discontinuations related to adverse events.
Time frame: Baseline through Month 14
Plan to share: Yes — Deidentified individual participant-level data underlying the reported results, together with a data dictionary, may be shared with qualified researchers after publication.
Supporting information: Study protocol, Statistical analysis plan, Analytic code
Time frame: Beginning after publication. No planned end date for data requests is specified.
Access criteria: Deidentified participant-level data and supporting information may be provided to qualified researchers whose proposed use is scientifically sound, upon reasonable written request to the corresponding author, subject to applicable institutional and ethics requirements and execution of an appropriate data-use agreement.
No publications or documents are linked to this record.
Ran from Mar 2024 to primary completion in Jan 2026, 22 months.
Of 112 non-industry phase 4 interventional studies under Obesity, half reached primary completion within 42 months of starting (the median), counting those still running; a quarter within 18 and three quarters within 81. This study's 22 months is below that.
Counting every sponsor, half of 127 studies reached it within 39 months; a quarter within 18 and three quarters within 70.
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 ↗
This study is completed, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: Phentermine