The potential role of phentermine in the treatment of obesity in the adult population of Mexico

BackgroundThe recently published Mexican guidelines for the management of obesity recommend the alternative use of phentermine for six months or more in adults, based on its low cost and wide availability. However, despite the extensive clinical use of phentermine, accurate information remains limited regarding the clinical appropriateness of selecting a 15 mg versus a 30 mg starting dose, as well as their respective efficacy expectations. This study was aimed to advance these aspects, based in the first month body weight reduction in kilograms (1mo-BWRkg) and month of tolerance development (moT) as efficacy predictors of 15 mg and 30 mg phentermine, on obese Mexicans.MethodsA comparative, prospective, multi-center, uncontrolled phase IV, open-label study was performed in 114 and 151 obese completer subjects treated for 6 months with daily 15 mg and 30 mg phentermine, respectively, between August 2015 and December 2018. Subjects were grouped into various 1mo-BWRkg, moT and 6mo-BWR% (six-month body weight reduction in percentage) intervals. Correlations between 1mo-BWRkg, moT and 1mo-BWRkg + moT with 6mo-BWR% efficacy and a multivariate analysis was performed to determine the impact of these parameters on the 6mo-BWR% efficacy with both phentermine doses.ResultsThe BWR% profile of 30 mg phentermine was only marginally superior to that of 15 mg phentermine. A large intrasubject variability in BWR% was observed with both interventions. 1mo-BWRkg + moT was found to be an acceptable parameter of 6mo-BWR% for 15 mg and 30 mg phentermine.ConclusionOur results suggest that once phentermine is selected for initial obesity treatment, starting with a 15 mg dose is a rational approach. An advantage of phentermine is that its 6mo-BWR% effectiveness can be predicted early and progressively. Furthermore, phentermine seems to be a viable long-term alternative to the newer, highly effective, and costly weight-loss drugs for acquisition of healthy lifestyle habits, the improvement of quality of life and life expectancy, and the prevention of health risks in the Mexican population, but requires confirmatory prospective controlled studies.