Is it safe to take prescribed phentermine in the presence of known right bundle branch block (RBBB)?

Is prescribed phentermine safe to take with a RBBB? The RBBB was only detected by EKG. No symptoms in otherwise healthy 37 y/o male. Just need to lose 30-40 lbs.

Submitted by Tom from Dallas, Texas on 07/13/2017

by Michael J. Mihalick, MD

Dear Tom,
There is no data to answer your question. Most cardiologists are not fans of appetite suppressants since they are all members of the amphetamine family and are associated with arrhythmias and hypertension. This is more likely in some individuals. Whether your RBBB puts you in this category, I don’t know. As you may know, the combination of phentermine and fenfluramine (PhenFen) was associated with significant cardiac issues. Fenfluramine was taken off the market, but phentermine remains. Currently, successfully losing weight and maintaining it is accomplished in two ways: permanently changing your eating habits, and bariatric surgery. Bariatric surgery is not fully effective in the absence of a permanent dietary change along with an exercise program. The rationale for appetite suppressants is to temporarily suppress the appetite while the patient is in the process of changing his eating habits. However, these drugs are usually only effective for one or two weeks at most. Perhaps more effective and safer drugs will be available in the future, but for now there is ‘no free lunch’ (no pun intended).