What medication doses need adjustment in a patient with impaired renal function on metformin, Atacand Plus (candesartan/hydrochlorothiazide), and rosuvastatin?

Medication Dose Adjustments for Patient with Impaired Renal Function

Based on the patient's eGFR of 44 ml/min/1.73m², metformin dose should be reduced to 1000 mg daily (half the current dose), Atacand Plus should be discontinued, and rosuvastatin should be maintained at the current dose with close monitoring.

Assessment of Renal Function

The patient has moderate renal impairment with:

• eGFR: 44 ml/min/1.73m²
• Serum creatinine: 112 μmol/L
• Urea: 10.4 mmol/L
• B12: 105 (low)

Medication Adjustments Required

1. Metformin Adjustment

• Current dose: 2000 mg daily
• Recommended adjustment: Reduce to 1000 mg daily (50% dose reduction)
• Rationale: For patients with eGFR 30-44 ml/min/1.73m², the KDIGO guidelines recommend halving the metformin dose 1.
• Monitoring requirements:
  • Increase renal function monitoring to every 3-6 months
  • Monitor for vitamin B12 deficiency (already present at 105)
  • Supplement vitamin B12 due to current deficiency

2. Atacand Plus (Candesartan/HCTZ) Adjustment

• Current dose: 16/12.5 mg
• Recommended adjustment: Discontinue combination product and switch to candesartan alone
• Rationale:
  • Hydrochlorothiazide component is less effective and potentially harmful with eGFR <30 ml/min/1.73m²
  • Combination product dosing recommendations cannot be provided for patients with creatinine clearance <30 ml/min 2
  • The combination of metformin with diuretics and candesartan increases risk of acute kidney injury 3

3. Rosuvastatin Adjustment

• Current dose: 20 mg daily
• Recommended adjustment: Maintain current dose with monitoring
• Rationale:
  • No dosage adjustment is required for moderate renal impairment
  • Only severe renal impairment (CrCl <30 ml/min/1.73m²) requires dose limitation to 5-10 mg 4

Additional Considerations

Vitamin B12 Deficiency

• Patient's B12 level is 105, which is low
• This is likely related to long-term metformin use 1
• Recommendation: Start vitamin B12 supplementation

Drug Interactions

• Monitor for potential interactions between rosuvastatin and metformin, although clinical studies show no significant pharmacokinetic interaction requiring dose adjustment 5
• The combination of diuretic, candesartan, and metformin increases risk of lactic acidosis in setting of acute kidney injury 3

Monitoring Plan

1. Check renal function every 3 months
2. Monitor for signs of lactic acidosis (nausea, vomiting, malaise, abdominal pain)
3. Recheck B12 levels after supplementation
4. Monitor blood pressure after discontinuing hydrochlorothiazide component

Warning Signs Requiring Immediate Attention

• Acute decline in renal function
• Signs of lactic acidosis (abdominal pain, hyperventilation, malaise)
• Significant hypotension after medication changes

Algorithm for Ongoing Medication Management

1. If eGFR improves to >45 ml/min/1.73m²: Consider increasing metformin dose
2. If eGFR declines to <30 ml/min/1.73m²: Discontinue metformin and reduce rosuvastatin to 5-10 mg daily
3. If blood pressure control inadequate after HCTZ discontinuation: Consider adding alternative antihypertensive that is safe in renal impairment

This medication adjustment plan prioritizes patient safety by reducing the risk of lactic acidosis from metformin while maintaining effective treatment of diabetes, hypertension, and hyperlipidemia in the setting of moderate renal impairment.