A comparative study of phentermine and diethylpropion in the treatment of obese patients in general practice.

A study was carried out in general practice to compare the effectiveness and tolerance of phentermine and diethylpropion in helping patients more than 20% above their desirable weight to lose weight. Patients were allocated at random to receive either one 30 mg capsule of phentermine (50 patients) or one 75 mg tablet of diethylpropion (49 patients) daily over a period of 12 weeks. They were also asked to restrict their calorie intake to 1500 calories per day. The results showed that there was a significantly greater weight loss in patients treated with phentermine which was particularly marked during the last 4 weeks of the study. There were significant reductions in blood pressure and heart rate in the phentermine group and of heart rate in the diethylpropion group. These were almost certainly related to weight loss rather than to a direct effect of drug treatment. Side-effects were generally minor in nature and the incidence and nature of them were comparable in the two groups.