(Note: Not all drug interactions are known or reported in the literature, and new drug interactions are continually being reported. This information is provided only for your education and for you to discuss with your personal healthcare provider. )
VENLAFAXINE HYDROCHLORIDE (in Effexor Tablets) may interact with PHENTERMINE (in Phentermine Tablets)
Although the cause of this potential interaction is not clearly understood, venlafaxine may increase the effects of phentermine. This could cause an increase in side effects including irritability and depression, restlessness, and anxiety. Other more serious side effects include an increase in blood pressure, a rapid heart beat, and an abnormal heart rhythm. If venlafaxine and phentermine are used together, your doctor may want to monitor you closely for side effects and adjust the dose of either drug if needed. Discuss this potential interaction with your healthcare provider at your next appointment, or sooner if you think you are having problems.
This interaction is poorly documented and is considered moderate in severity.