Phentermine-Topiramate Use in Patients with Cardiovascular Disease and Kidney Stone Risk

Introduction to Phentermine-Topiramate Contraindications

The American Gastroenterological Association recommends that phentermine-topiramate should be avoided in patients with a history of cardiovascular disease, including coronary artery disease, stroke, arrhythmias, congestive heart failure, or uncontrolled hypertension 1, 2

Phentermine is a sympathomimetic amine that activates the adrenergic system, causing increases in heart rate and blood pressure through norepinephrine elevation in the central nervous system, which can exacerbate underlying coronary artery disease and precipitate adverse cardiovascular events 4, 2
No large cardiovascular outcome trials exist for long-term phentermine-topiramate use, leaving safety in cardiovascular disease patients unestablished 1, 2
For patients with cardiovascular disease requiring weight loss pharmacotherapy, GLP-1 receptor agonists, such as semaglutide or liraglutide, represent safer alternatives with demonstrated cardiovascular benefits 5

Topiramate has carbonic anhydrase inhibitor properties that induce metabolic acidosis, elevated urine pH, hypercalciuria, and hypocitraturia, all of which increase kidney stone risk, particularly with higher doses and prolonged exposure 1
Caution is advised in patients with a history of significant nephrolithiasis 1
Periodic monitoring of serum bicarbonate levels should be implemented for patients on long-term therapy 1

The recommended starting dose is 3.75 mg/23 mg once daily for 14 days, with escalation to a maintenance dose of 7.5 mg/46 mg daily 4, 1
Blood pressure and heart rate monitoring should be performed at every visit 1, 5, 3
Monthly pregnancy tests should be conducted for women of childbearing potential, as topiramate is teratogenic 1, 3

Do not prescribe phentermine-topiramate within 14 days of MAOI use due to hypertensive crisis risk 3
Do not use phentermine-topiramate in untreated hyperthyroidism due to arrhythmia and seizure concerns 1, 3
Be aware of potential perioperative complications, including hypertensive crises, hypotension, bradycardia, and hyperthermia, in patients requiring general anesthesia 6