Objective: To determine if patients taking prescribed phentermine long-term who quit taking the drug develop any signs of an amphetamine-like withdrawal syndrome.

Date of Research Idea: December 2007.

Collaborator: Frank L. Greenway, M.D., Pennington Biomedical Research Center, Louisiana State University.

Description: A retrospective observational study of patients who had chosen to cease taking phentermine. The patients were examined for signs or symptoms characteristic of amphetamine-like withdrawal. All subjects were from my practice.

Funding: Hendricks for Health


·      Patients had no withdrawal symptoms other than a return of hunger and poorly controlled eating.

·      Patients did not crave phentermine. (Drug craving is a hallmark symptom of addiction).

Presented at:

·      Hendricks EJ. Is Phentermine Addicting? 59th Annual Obesity & Associated Conditions Symposium. Costa Mesa: American Society of Bariatric Physicians, 2009.

·      Hendricks EJ, Greenway FL. Symptoms Observed after Abrupt Phentermine Cessation. 27th Annual Scientific Meeting. Washington, D.C.: The Obesity Society, 2009.


·      Hendricks EJ, Greenway FL. A Study of Abrupt Phentermine Cessation in Patients in a Weight Management Program. American Journal of Therapeutics 2011; 18(4): 292-9.

Elapsed time: ~ 3 years, 5 months.

Significance: After no reports of abuse or addiction appeared during 50+ years of widespread use the FDA and DEA still maintain phentermine is potentially addicting. This was the first-ever post-marketing report concerning phentermine addiction potential. We found no evidence that phentermine is an addicting substance.