Addiction potential of phentermine prescribed during long-term treatment of obesity.

OBJECTIVE

To investigate if phentermine treatment induces phentermine abuse, psychological dependence (addiction) or phentermine drug craving in overweight, obese and weight loss maintenance patients. To investigate whether amphetamine-like withdrawal occurs after abrupt cessation of long-term phentermine treatment.

DESIGN

Clinical intervention trial with interruption of phentermine treatment in long-term patients.

SUBJECTS: 269 obese, overweight or formerly obese subjects (age: 20-88 years, BMI: 21-74 kg m(-2)) treated with phentermine long-term (LTP, N=117), 1.1-21.1 years, or short-term (ATP, N=152), 4-22 days, with phentermine doses of 18.75-112.5 (LTP) and 15-93.75 (ATP) mg per day.

MEASUREMENTS: Module K of the Mini International Neuropsychiatric Interview modified for phentermine (MINI-SUD), Severity of Dependence Scale (SDS), 45-item Cocaine Craving Questionnaire-NOW (CCQ-NOW) modified for phentermine (PCQ-NOW), and Amphetamine Withdrawal Questionnaire (AWQ) modified for phentermine (PWQ).

RESULTS

MINI-SUD interviews were negative for phentermine abuse or psychological dependence in all LTP patients. SDS examination scores were low for all LTP and ATP patients, indicating they were not psychologically dependent upon phentermine. PCQ-NOW scores were low for all LTP and ATP patients, indicating neither short-term nor long-term phentermine treatment had induced phentermine craving. Other than an increase in hunger or eating, amphetamine-like withdrawal symptoms did not occur upon abrupt phentermine cessation as measured by sequential PWQ scores.

CONCLUSIONS

Phentermine abuse or psychological dependence (addiction) does not occur in patients treated with phentermine for obesity. Phentermine treatment does not induce phentermine drug craving, a hallmark sign of addiction. Amphetamine-like withdrawal does not occur upon abrupt treatment cessation even at doses much higher than commonly recommended and after treatment durations of up to 21 years.