Objective: To determine cardiovascular safety and effectiveness of long-term phentermine treatment.

Date of Research Idea: October 2009.

Collaborators: Eric C. Westman, M.D., Duke University, Frank L. Greenway, M.D., Pennington Biomedical Research Center, Louisiana State University. Alok K. Gupta, M.D., Pennington Biomedical Research Center

Description: A retrospective observational study of 300 sequential returning patients treated with low-carbohydrate ketogenic diets and either phentermine or no anti-obesity drug. All subjects were from my practice.

Funding: American Society of Bariatric Physicians.


 ·      Patients with initially elevated blood pressures had lowered blood pressure with weight loss – treated with or without phentermine.

 ·      Patients treated with phentermine had more persistent weight loss and blood pressure lowering effects than did patients untreated with phentermine.

 ·      Progression to prehypertension and hypertension was retarded or reversed in phentermine-treated patients.

 ·      The latter two findings, that phentermine treatment induces improvement in cardiovascular profiles, suggest strongly that long-term phentermine treatment can reduce cardiovascular mortality in obese subjects.

 Presented at:

 ·      Hendricks EJ. Long-term Phentermine: Weight Loss, Blood Pressure, & Heart Rate Effects. American Society Bariatric Physicians 60th Annual Obesity Seminar. New Orleans, 2010.

 ·      Hendricks EJ, Greenway F, Westman E, Gupta AK. Phentermine pharmacotherapy for Weight Management in Overweight to Morbidly Obese Subjects does not alter seated resting office blood pressure 475P The Obesity Society Annual Scientific Meeting 2010.


 ·      Hendricks EJ, Greenway FL, Westman EC, Gupta AK. Blood pressure and heart rate effects, weight loss and maintenance during long-term phentermine pharmacotherapy for obesity. Obesity (Silver Spring) 2011; 19(12): 2351-60.

 Elapsed time: ~ 4 years, 2 months.

 Significance: This study refutes the commonly held presumption that phentermine treatment can induce elevations in blood pressure. Instead, phentermine treatment for overweight and obese patients with pre-existing elevations of blood pressure lowers blood pressure. This effect is most pronounced in patients with hypertension but the effect also occurs in prehypertensive patients. Another highly significant finding is that weight loss due to phentermine treatment retards the expected progression from prehypertension to hypertension. These findings were recently confirmed by a retrospective analysis of data from clinical trials for phentermine/topiramate (Qsymia). These two studies strongly suggest that phentermine and phentermine/topiramate therapy for obesity can lower cardiovascular risk for heart attack and stroke and therefore can help lower mortality rates in obese patients. The presumption that phentermine is hazardous and should be withheld from patients with heart disease is false; the truth is overweight and obese patients with heart disease can derive the greatest benefit from phentermine therapy.