This medication can rarely cause serious (sometimes fatal) lung or heart problems (pulmonary hypertension, heart valve problems). The possible link between phentermine and heart failure is due to rare reports of valvular heart disease in people who took the medication. The medication can also cause pulmonary hypertension, which can be fatal. Common phentermine side effects include nausea, vomiting, diarrhea, constipation, dry mouth, restlessness, nervousness, headaches, tremors, and insomnia.
You have a very small risk of addiction. The main adverse cardiovascular effects are palpitations, mild tachycardia and high blood pressure. Cardiovascular contraindications for the use of phentermine include a history of coronary artery disease, stroke, arrhythmias, congestive heart failure, and uncontrolled hypertension. AF has not been a well-described adverse effect of phentermine.
To our knowledge, phentermine-induced AF has only been described twice in the literature. Sometimes, instead of prescribing phentermine alone, doctors prescribe a medication that combines phentermine with topiramate.