Can Phentermine Cause Chest Pain, Lightheadedness, and Dizziness?
Yes, phentermine can cause chest pain, lightheadedness, and dizziness—these are recognized cardiovascular and central nervous system adverse effects that occur through sympathetic nervous system activation. 1
Cardiovascular Effects Leading to Chest Pain
The FDA drug label explicitly lists "ischemic events" as a cardiovascular adverse reaction to phentermine, which can manifest as chest pain or angina pectoris 1
Phentermine causes palpitations, tachycardia, and elevation of blood pressure through its sympathomimetic effects, all of which can contribute to chest discomfort 1
Patients should be advised to report immediately any deterioration in exercise tolerance, new unexplained dyspnea, angina pectoris, or syncope, as these may indicate serious cardiovascular complications including pulmonary hypertension 1
Rare but serious cardiac events include primary pulmonary hypertension and regurgitant cardiac valvular disease, though the valvular disease risk was primarily associated with the discontinued fenfluramine combination, not phentermine alone 1, 2
Central Nervous System Effects Causing Dizziness and Lightheadedness
The FDA label identifies "dizziness" as a specific central nervous system adverse reaction to phentermine 1
Additional CNS effects include overstimulation, restlessness, insomnia, euphoria, dysphoria, tremor, and headache—all of which can contribute to lightheadedness 1
Phentermine may impair the ability to engage in potentially hazardous activities such as operating machinery or driving due to these CNS effects 1
Mechanism of These Adverse Effects
Phentermine is a norepinephrine-releasing agent that activates the sympathetic nervous system, which explains both the cardiovascular stimulation (chest pain, palpitations) and CNS stimulation (dizziness, restlessness) 3
The drug has pharmacologic activity similar to amphetamine, accounting for its stimulant-related side effects 1
High-Risk Populations
Phentermine is absolutely contraindicated in patients with a history of cardiovascular disease, including coronary artery disease, stroke, arrhythmias, congestive heart failure, or uncontrolled hypertension 4, 5, 1
Even patients with mild hypertension require caution when prescribing phentermine due to the risk of blood pressure elevation 1
Case reports document atrial fibrillation and ischemic stroke associated with phentermine use, though these are rare events 6, 7
Critical Monitoring Requirements
Blood pressure and heart rate must be monitored at baseline and periodically throughout treatment to detect cardiovascular effects early 3, 4
Discontinue phentermine immediately if patients develop new chest pain, unexplained dyspnea, syncope, or lower extremity edema 1
The combination of phentermine with other sympathomimetic agents increases the risk of cardiovascular adverse effects and requires heightened monitoring 4
Common Pitfall to Avoid
Do not confuse phentermine monotherapy with the discontinued "fen-phen" combination (phentermine-fenfluramine)—the serious valvular heart disease and pulmonary hypertension risks were attributed to fenfluramine, not phentermine 4, 1
However, the possibility of an association between valvular heart disease and phentermine alone cannot be completely ruled out, as rare cases have been reported 1