Obesity is an illness which is harder to treat than many cancers. Doctors and patients have been looking for a pharmacological approach coupled with proper nutrition and regular exercises to cope with chronic obesity. One of the most popular drug for that purpose is phentermine. Once widely praised as a “wonder drug”, phentermine still boasts as the most commonly prescribed appetite suppressant in the US, one of the reason being its cheaper price tag compared to other similar drugs.
Phentermine HCl enhances the levels of several neurotransmitters including dopamine and norepinephrine affecting blood flow, heartbeat, and reactivity to stress. This makes people eat more rapidly but to eat less. Another appetite suppressant, fenfluramine, acts on a different neurotransmitter, serotonin. Serotonin is involved in controlling mood and reduces the feelings of agitation associated with hunger.
Phentermine is a generic name, which is sold under various brand names including Ionamin, Adpex-P, Fastin, etc. Phentermine first became available for consumers in the late 50s, and later modified as Phentermine Hydrochloride (HCl) in the 70s. Phentermine became popular again in the 90s in the form of ‘cocktail’, Fen-Phen. In 1992, Dr. Weintraub from University of Rochester School of Medicine and Dentistry published a paper.
While phentermine and fenfluramine are both approved by FDA separately, their mixture, ‘Fen-Phen’ never was, and their prescription by doctors was considered off-label. Dexfen-Phen is another combination including phentermine. In this case, the other ingredient is dexfenfluramine or redux. Dexfenfluramine was also used as an appetite suppressant. Dexfen-Phen again followed the suit, and became widely popular.
In 1997, Mayo Clinic reported 24 cases of heart valve disease in the patients who had taken fen-phen cocktail. Further findings suggested fenfluramine and dexfenfluramine may be related to heart valve disorder, and accordingly, FDA issued a public health advisory and requested drug manufacturers to voluntarily withdraw fenfluramine and dexfenfluramine.
Unlike fenfluramine and dexfenfluramine, phentermine was not taken off the market. Phentermine is again used in various cocktail forms. It was necessary since phentermine’s appetite suppressing effect decreases rather rapidly over time.