In 1997, the popular weight loss medication combination "fen-phen" (fenfluramine + phentermine) was found to cause heart valve problems. The problem was linked to fenfluramine (Pondimin) which was pulled from the market along with a similar medication, dexfenfluramine (Redux). These medications worked by stimulating a serotonin receptor known as the 5-HT2 receptor. When 5-HT2 receptors are stimulated in the brain, appetite shuts down. But 5-HT2 receptors in the heart also were stimulated, leading to heart valve problems.
The second half of the fen-phen combination, phentermine (Adipex, Suprenza, Lomaira) was not removed from the market and remains a mainstay of obesity treatment. Phentermine is found in the combination medication Qsymia which contains long-acting versions of phentermine and topiramate (Topamax).
Belviq and Belviq XR (lorcaserin) are second-generation versions of fenfluramine that are considered safe for the heart because they are specific for the 5-HT2c receptor which is only found in appetite centers of the brain. The heart contains 5-HT2b receptors which are unaffected by lorcaserin. In fact, lorcaserin is the preferred weight loss medication for patients with heart disease.
Many of my patients who took fenfuramine or dexfenfluramine in the past have told me that feeling they get with Belviq is similar to these medications. SSRI medications such as Prozac, Paxil and Zoloft work by inhibiting the reuptake of serotonin and should be avoided while taking Belviq. Belviq has the lowest side effect profile of any of the weight loss medications, and most side effects were seen at similar rates as a placebo pill. The most common side effects are headache, dizziness and dry month.
There was a study published in the May 2017 issue of the journal Obesity evaluating the safety and efficacy of Bel-phen, which is the combination of lorcaserin and phentermine. This study found that Bel-phen was safe and highly effective combining distinct yet complimentary mechanisms of action of the two medications. Weight loss medications work best when combined with a healthy low-calorie diet and regular physical activity. I have found that the keto diet works especially well with this medication combination.
If you’d like to learn more about anti-obesity medications, please feel free to call us or schedule an appointment with Dr. Isaacs using the online booking tool on this website.