In a 63-year-old man taking furosemide (Lasix), metformin (Glucophage), insulin glargine (Lantus Solostar), tirzepatide (Mounjaro), lisinopril, hydrochlorothiazide (Hydrodiuril), naloxone (Narcan), empagliflozin (Jardiance), cholecalciferol (vitamin D3), aspirin, atorvastatin (Lipitor), budesonide‑formoterol (Symbicort), ibuprofen, gabapentin (Neurontin), and various medical supplies, which of these medications are associated with an increased risk of nephrolithiasis (kidney stones)?

Medication-Associated Kidney Stone Risk

Among this patient's medications, hydrochlorothiazide (25 mg) and furosemide (20 mg) are the primary concerns for kidney stone formation, with vitamin D supplementation (2,000 units) and ibuprofen (800 mg) as secondary considerations.

High-Risk Medications

Loop and Thiazide Diuretics

Furosemide (Lasix) carries FDA-documented risk for nephrocalcinosis/nephrolithiasis, particularly noted in premature infants but relevant across populations 1. The mechanism involves alterations in urinary calcium excretion and potential dehydration effects.

Hydrochlorothiazide (25 mg) presents a paradoxical situation: while thiazide diuretics are actually recommended for preventing recurrent calcium stones at higher doses (50 mg hydrochlorothiazide) 2, the 25 mg dose this patient receives is lower than studied prevention doses. At standard treatment doses for hypertension, thiazides can still affect urinary calcium and electrolyte balance, though the net effect at this dose is unclear from the evidence.

Critical distinction: The 2014 American College of Physicians guidelines recommend thiazides (hydrochlorothiazide 50 mg, chlorthalidone 25-50 mg) specifically to prevent recurrent nephrolithiasis 2. However, these are higher doses than what this patient receives for blood pressure control. The stone-protective effect requires adequate dosing and is based on reducing urinary calcium excretion.

Vitamin D Supplementation

Cholecalciferol (2,000 units daily) can increase intestinal calcium absorption and potentially urinary calcium excretion, theoretically increasing calcium stone risk. However, this is a moderate dose, and the evidence linking standard vitamin D supplementation to stone formation is primarily theoretical rather than definitively established in clinical trials.

NSAIDs

Ibuprofen (800 mg) has documented interactions with loop diuretics that can affect renal function 1. While not directly lithogenic, NSAIDs can impair renal function and alter the urinary environment. The combination with furosemide warrants monitoring.

Low-Risk or Protective Medications

The following medications have no established association with kidney stone formation:

• Metformin - No lithogenic properties
• Insulin glargine - No stone risk
• Tirzepatide (Mounjaro) - Recent evidence suggests potential kidney-protective effects with slowed eGFR decline 3; no stone association
• Lisinopril - ACE inhibitors not associated with stones
• Empagliflozin (Jardiance) - SGLT2 inhibitors not linked to nephrolithiasis
• Aspirin - No direct stone risk
• Atorvastatin - No lithogenic properties
• Budesonide-formoterol - Inhaled corticosteroids have minimal systemic effects at standard doses
• Gabapentin - No documented stone risk 4
• Naloxone - No stone association

Clinical Management Recommendations

Immediate Actions

1. Review hydration status: Ensure patient maintains urine output ≥2 L/day, the primary prevention strategy per ACP guidelines 2

2. Monitor electrolytes: Both furosemide and hydrochlorothiazide require periodic monitoring of calcium, potassium, and renal function 1

3. Assess stone history: If patient has had prior stones, consider:

   • Stone composition analysis if available
   • 24-hour urine collection for metabolic evaluation
   • Potential dose adjustment of diuretics if recurrent stones develop

Medication Adjustments to Consider

• If stones develop: The hydrochlorothiazide dose could potentially be increased to 50 mg (if blood pressure allows) for stone prevention rather than discontinued, based on ACP guidelines 2
• Furosemide: Consider whether this can be minimized or whether alternative diuretic strategies exist
• Vitamin D: Reassess necessity of supplementation if hypercalciuria documented
• Ibuprofen: Use sparingly given interaction with diuretics and renal effects

Common Pitfalls

Do not automatically discontinue thiazide diuretics if stones develop - at appropriate doses (≥50 mg hydrochlorothiazide), they actually prevent calcium stone recurrence 2. The current 25 mg dose is subtherapeutic for stone prevention.

Avoid assuming all diuretics are equivalent - loop diuretics (furosemide) and thiazides have different effects on calcium handling and stone risk.

Remember that dehydration is the primary modifiable risk factor - medication effects are secondary to adequate fluid intake 2.