Phentermine/Topiramate for Uric Acid Stones

Inclusion Criteria: * have recurrent pure uric acid nephrolithiasis (UAN) or mixed calcium oxalate (CO)/UAN. Recurrent stone disease is defined as at least two spontaneous kidney stone passages, two previous kidney stone procedures, or one previous stone passage and one previous procedure. Pure UAN is defined as at least one previous stone analysis demonstrating 100% uric acid mineral content. Mixed COUAN will be defined as at least one previous stone analysis with any mix of uric acid ≥80% and ≤20% calcium oxalate. If participant has more than one stone analysis, the most recent will be considered the current stone type. * have obesity, defined as BMI \> 30 kg/m2. * have type 2 diabetes mellitus or pre-diabetes, defined as previously diagnosed by laboratory testing (hemoglobin A1c, fasting plasma glucose, or oral glucose tolerance test) or as demonstrated by use of anti-hyperglycemic medications or insulin. * have at least one 24-hour urine study off medications demonstrating urine pH \< 5.8 or a study 24-hr urine demonstrating urine pH \< 5.8 Exclusion Criteria: * contraindications to topiramate, including: recurrent major depression, current substantial depressive symptoms, uncontrolled depression by PHQ 9 score \>= 10, history of suicidal ideation or behavior with intent to act (versus exclude those with depression); current pregnancy or attempting to conceive; pre-existing chronic kidney disease with eGFR \< 60 at time of enrollment; active cancer or active treatment for cancer (chemotherapy, radiation); and non-ambulatory. * contraindications to phentermine, including: unstable cardiovascular disease defined as decompensated heart failure, unstable angina, atrial fibrillation, uncontrolled blood pressure (\>160 systolic), hyperthyroidism; monoamine oxidase inhibitor use; current history of drug or alcohol abuse.