Should a patient in her 70s with impaired renal function (GFR of 32) continue taking olmesartan (angiotensin II receptor antagonist) 40mg?

Management of Olmesartan in a Patient with Impaired Renal Function

Olmesartan should be discontinued in this elderly patient with a GFR of 32 mL/min and an alternative antihypertensive medication should be initiated. 1

Assessment of Current Situation

This patient presents with several concerning factors:

• Elderly patient in her 70s
• Severely impaired renal function (GFR of 32 mL/min), which falls into the G3b category (moderate-severe decrease in renal function) 2
• Currently on a high dose of olmesartan (40 mg)

Rationale for Discontinuation

1. Renal Impairment Considerations:

   • According to the FDA drug label, patients with severe renal impairment (creatinine clearance <20 mL/min) have approximately tripled AUC (area under the curve) of olmesartan compared to those with normal renal function 1
   • While this patient's GFR of 32 mL/min doesn't meet the definition of severe impairment, it falls into the moderate-severe category, suggesting significant risk

2. Dosing Concerns:

   • The FDA label specifically states that "no initial dosage adjustment is recommended for patients with moderate to marked renal impairment" but also notes that for patients with severe renal impairment, "consideration should be given to a lower starting dose" 1
   • This patient is already on the maximum recommended dose (40 mg) despite impaired renal function

3. Age-Related Factors:

   • Pharmacokinetic studies show that elderly patients (65-75 years) have up to 44% higher steady-state Cmax and AUC values compared with younger patients 3
   • Elimination half-life is also longer in elderly patients (12.8h vs 10.6h in younger patients) 3
   • These age-related changes compound the renal impairment concerns

Alternative Management Options

1. Consider an alternative antihypertensive agent:

   • Calcium channel blockers or dihydropyridine calcium channel blockers may be more appropriate as they have less impact on renal function 4
   • If an ARB is still desired, consider a lower dose of an alternative ARB with less renal excretion

2. If continuing ARB therapy is deemed necessary:

   • Reduce the olmesartan dose to 20 mg daily or lower 1
   • Monitor renal function and electrolytes closely (within 1-2 weeks after medication change) 4

Monitoring Recommendations

If any antihypertensive therapy is continued or modified:

• Check renal function (serum creatinine, eGFR) and electrolytes within 1-2 weeks after medication change 4
• Continue monitoring renal function every 2-4 weeks initially, then every 3 months if stable 4
• Monitor blood pressure regularly to ensure adequate control
• Watch for signs of worsening renal function or hyperkalemia

Important Considerations

• ARBs like olmesartan can cause an initial decline in GFR due to their effect on efferent arteriolar vasodilation 2
• A 10-20% increase in serum creatinine can be anticipated and is not necessarily a reason to discontinue therapy 2
• However, in this case, the patient already has significantly impaired renal function, making the risk-benefit ratio unfavorable for continuing high-dose olmesartan

Conclusion

Given this patient's age and degree of renal impairment, the high dose of olmesartan (40 mg) presents significant risks. The most prudent approach is to discontinue olmesartan and switch to an alternative antihypertensive medication with a more favorable renal profile, or at minimum, reduce the olmesartan dose substantially while monitoring renal function closely.