A popular drug for treating obesity Phentermine has a high safety profile. However, it interacts with other anorectics that may cause various undesirable reactions.
For example, during Phentermine interaction with Bupropion and Naltrexone, risk of convulsions increases.
Simultaneous use of Phentermine with other anorectics may cause a variety of cardiovascular events, such as:
- Cardiac fibrosis
- Primary pulmonary hypertension
- Raise in blood pressure
Pharmacodynamic interaction of Phentermine with other amphetamine-type anorectics is related to their effect on serotonin receptors. These weight loss drugs possess a synergistic potential and can enhance therapeutic effect of Phentermine.The mechanism of Phentermine interaction with these anorectics is to increase serotonin concentration that may cause narrowing of blood vessels, blood circulation disorder or myocardial hypertrophy.
The results of several clinical studies prove a potential of pulmonary hypertension or cardiac valvulopathy when using Phentermine together with Dexfenfluramine or Fenfluramine.
- When Phentermine interacts with one of these anorectics, an incidence of heart valve diseases is less than 6%.
- When using Phentermine with Fenfluramine, a probability of this cardiovascular event increases to about 80%.
At the end of the 20th century, the FDA banned simultaneous use of Phentermine with Fenfluramine and Dexfenfluramine because of the high risk of cardiovascular complications, such as damage to the heart valves or pulmonary hypertension.
In addition, because of the high cardiovascular risk associated with potential drug interaction, Phentermine is contraindicated in combination with such anorectics as Methamphetamine, Phendimetrazine, Benzphetamine, Lorcaserin, or Diethylpropion.