The potential link between phentermine and heart failure is due to rare reports of valvular heart disease in people who took the medication. Phentermine can also cause pulmonary hypertension, which can be fatal. Prolonged use of phentermine can lead to physical and psychological dependence, and if stopped abruptly, a withdrawal reaction may occur, including excessive sleepiness, fatigue, tremors, and depression. A study found that patients who took long-term phentermine and stopped taking it due to their own choice did not experience an amphetamine-like withdrawal symptom complex.
Despite this, fear of the adverse effects of phentermine has caused some doctors to reduce its use for the treatment of obesity. To further investigate the addictive potential of phentermine, a prospective study will evaluate patients who have been taking it long-term for two years or more using validated psychometric scales. This is based on the structural chemical similarities between phentermine and amphetamine, as well as evidence in rats that phentermine stimulates spontaneous activity. A retrospective study looked into the symptoms that occur when patients treated with long-term phentermine in a weight management program abruptly stopped taking it.
Participating patients who have taken long-term phentermine in this study will be asked to discontinue phentermine treatment for 48 hours to participate in the study. Overall, it is important to be aware of the potential risks associated with taking phentermine for long periods of time. It is recommended to consult with a doctor before starting any medication.