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Phentermine vs Placebo for Weight Loss in Obese Patients, Diabetes, Obesity, and Metabolism (2010) [PubMed abstract]
  • The trial enrolled 74 obese patients with an average BMI of 33
Main inclusion criteria
  • BMI ≥ 30 or BMI 27 - 30 and treated for type 2 diabetes, hypertension, or dyslipidemia
Main exclusion criteria
  • HgA1C > 7.5%
  • SBP ≥ 140, DBP ≥ 90
  • History of weight loss surgery or medications
  • Psychiatric illness
Baseline characteristics
  • Average age 35 years
  • Average BMI - 33
  • Average weight - 191 lbs (87 kg)
  • Female sex - 74%
  • Average blood pressure - 123/80
Randomized treatment groups
  • Group 1 (37 patients) - Phentermine 30 mg once daily for 12 weeks
  • Group 2 (37 patients) - Placebo for 12 weeks
  • Phentermine was given in a diffuse-controlled release (DCR) capsule
  • All patients were instructed to follow a hypocaloric diet (1500 cal/day for men, and 1200 cal/day for women)
Primary outcome: Change in body weight and waist circumference at 12 weeks
Results

Duration: 12 weeks
Outcome Phentermine Placebo Comparisons
Primary outcome (body weight loss) 17.8 lbs (8.1 kg) 3.74 lbs (1.7 kg) p<0.001
% weight loss 10.7% 1.9% p<0.001
Primary outcome (decrease in waist circumference) 7.2 cm 2.1 cm p<0.001
Dropout rate 19% 27% N/A
  • Insomnia and dry mouth occurred significantly more in the phentermine group
  • Average blood pressure decreased in both groups over the course of the study, and the difference between groups was not significant [10]

Findings: Short-term phentermine DCR treatment resulted in significant reduction in weight and improvement of metabolic parameters, including waist circumference and some lipid profiles, without clinically severe adverse events. Further study is needed to show long-term efficacy and safety of phentermine DCR in Korean patients with obesity.
Diethylpropion vs Placebo for Weight Loss in Obese Patients, Int J of Obesity (2009) [PubMed abstract]
  • The trial enrolled 69 obese patients with an average BMI of 37
Main inclusion criteria
  • BMI ≥ 30 and ≤ 45
Main exclusion criteria
  • Body weight fluctuations > 4 kg in previous 3 months
  • Use of other weight loss medications
  • Diabetes
  • Significant depression, anxiety, or substance abuse disorder
Baseline characteristics
  • Average age 37 years
  • Average BMI - 37
  • Average weight - 211 lbs (96 kg)
  • Female sex - 90%
  • Average blood pressure - 126/72
Randomized treatment groups
  • Group 1 (37 patients) - Diethylpropion SR 50 mg twice a day for six months
  • Group 2 (32 patients) - Placebo for six months
  • All patients were instructed to follow a 600 calorie deficit per day diet
  • EKGs and echocardiograms were performed at baseline, 6 months, and 12 months
Primary outcome: Percent change in body weight at 6 months
Results

Duration: 6 months
Outcome Diethylpropion Placebo Comparisons
Primary outcome (% weight loss) 9.8% 3.2% p<0.0001
Average weight loss at 6 months 20.5 lbs (9.3 kg) 6.8 lbs (3.1 kg) p<0.0001
Dropout rate 19% 31% N/A
Dry mouth (first 3 months) 69.4% 41% p=0.02
Insomnia (first 3 months) 53% 22% p=0.009
  • Average blood pressure decreased in both groups over the course of the study, and the difference between groups was not significant
  • In the diethylpropion group, there were no clinically relevant abnormal findings or worsening of baseline findings in EKGs and echocardiograms over the course of the study
  • At 6 months, patients were enrolled in an open-label extension phase for 6 additional months. At 12 months, the diethylpropion group lost an additional 1.76 lbs (0.8 kg). [2]

Findings: Diethylpropion plus diet produced sustained and clinically significant weight loss over 1 year. It seems to be safe in relation to cardiovascular and psychiatric aspects in a well-selected population.