Is phentermine contraindicated in a 55-year-old woman with a history of coronary artery disease and a prior ST-elevation myocardial infarction treated with a drug-eluting stent in the right coronary artery?

Phentermine is Absolutely Contraindicated in This Patient

Phentermine must not be used in a 55-year-old woman with a history of coronary artery disease and prior STEMI treated with a drug-eluting stent. The FDA label explicitly lists "history of cardiovascular disease (e.g., coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension)" as an absolute contraindication to phentermine use 1.

Why This Contraindication Exists

Sympathomimetic Cardiovascular Effects

• Phentermine is a sympathomimetic amine that increases central norepinephrine release, directly raising heart rate and blood pressure 2, 1.
• These hemodynamic effects create immediate cardiovascular risk in patients with established coronary artery disease, potentially precipitating myocardial ischemia, arrhythmias, or acute coronary events 2.

Evidence of Serious Cardiac Events

• Case reports document ventricular fibrillation with coronary vasospasm following phentermine initiation in a patient with coronary disease 3.
• Supraventricular tachycardia and NSTEMI have been reported in patients taking phentermine, even in those without known prior coronary disease 4, 5.
• The sympathomimetic properties can enhance AV nodal conduction and increase atrial ectopy, triggering arrhythmias 5.

Post-STEMI Management Context

Stent Thrombosis Risk

• This patient has a drug-eluting stent in the RCA and requires strict adherence to dual antiplatelet therapy (aspirin plus a P2Y12 inhibitor such as clopidogrel, prasugrel, or ticagrelor) for at least 1 year 6.
• Premature discontinuation of dual antiplatelet therapy is the most important risk factor for acute stent thrombosis, which can lead to acute MI and death 7.
• Adding phentermine introduces unnecessary cardiovascular stress that could precipitate ischemic events or stent thrombosis in this high-risk patient 2, 1.

Standard Post-STEMI Care

• Aspirin should be continued indefinitely after PCI 6.
• P2Y12 inhibitor therapy (clopidogrel 75 mg daily, prasugrel 10 mg daily, or ticagrelor 90 mg twice daily) must continue for 1 year after drug-eluting stent placement 6.
• Newer-generation drug-eluting stents are associated with improved safety profiles compared with early-generation stents and are the standard of care for women undergoing percutaneous coronary revascularization 8.

Safe Alternative Weight-Loss Strategies

First-Line: GLP-1 Receptor Agonists

• Semaglutide 2.4 mg weekly or liraglutide 3.0 mg daily are the safest and most effective alternatives for this patient 2.
• These agents lack sympathomimetic activity and have demonstrated cardiovascular benefit in patients with established cardiovascular disease 2.
• Semaglutide dosing: start at 0.25 mg weekly and titrate to 2.4 mg over 16 weeks 2.
• Liraglutide dosing: start at 0.6 mg daily and escalate to 3.0 mg over 4 weeks 2.

Second-Line: Orlistat

• Orlistat 120 mg three times daily with meals blocks approximately 30% of dietary fat absorption 2.
• Expected weight loss is modest (mean 2.6 kg at 6 months, 2.9 kg at 12 months) but the medication has no cardiovascular contraindications 2.

Essential Lifestyle Modifications

• All pharmacologic strategies must be combined with reduced-calorie diet and increased physical activity 2.

Clinical Decision Algorithm

1. Immediately decline phentermine based on absolute FDA contraindication in patients with history of cardiovascular disease 1.
2. Counsel the patient that phentermine poses unacceptable cardiovascular risk given her history of STEMI and coronary stent 2, 1.
3. Offer GLP-1 receptor agonist (semaglutide or liraglutide) as first-line pharmacologic weight-loss therapy with superior efficacy and cardiovascular safety 2.
4. If GLP-1 agents are contraindicated or not tolerated, consider orlistat as a second-line option 2.
5. Ensure adherence to dual antiplatelet therapy and other evidence-based post-STEMI medications 6.

Critical Pitfalls to Avoid

• Never rationalize phentermine use by arguing that weight loss will eventually reduce cardiovascular risk; the immediate sympathomimetic threat outweighs any potential future benefit 2.
• Do not underestimate the risk based on the patient being relatively young (55 years) or having received a stent; the FDA contraindication applies to all patients with history of cardiovascular disease regardless of age or revascularization status 1.
• Avoid polypharmacy risks: combining phentermine with other cardiovascular medications could potentiate adverse effects, and the drug may interact with antihypertensive agents 1.