How to manage a patient with lightheadedness on Bendroflumethiazide (thiazide diuretic) and losartan (angiotensin II receptor antagonist) with impaired renal function?

Management of Lightheadedness in an 83-Year-Old Patient on Antihypertensives with Impaired Renal Function

The patient's lightheadedness is most likely due to medication-induced hypotension, and the best approach is to reduce the bendroflumethiazide (thiazide diuretic) dose or switch to a loop diuretic given the patient's impaired renal function (eGFR 36). 1

Assessment of Current Situation

• Patient presents with intermittent lightheadedness for 1 month, mostly in mornings, lasting ~1 minute 1
• Current medications include bendroflumethiazide (thiazide diuretic) and losartan (ARB) 2
• Blood pressure readings show no significant postural drop (131/71 sitting, 127/76 standing) 1
• Laboratory findings indicate impaired renal function with eGFR 36, creatinine 122 1

Medication Concerns in This Patient

• Thiazide diuretics (bendroflumethiazide) have reduced efficacy in patients with eGFR <30 mL/min/1.73 m² and may worsen renal function 1
• The combination of a thiazide diuretic with an ARB (losartan) increases the risk of hypotension, especially in elderly patients 1
• Losartan can cause symptomatic hypotension in volume-depleted patients or those on high doses of diuretics 2
• Renal function deterioration can occur with both ARBs and diuretics, particularly in patients with pre-existing renal impairment 2, 3

Management Plan

1. Medication Adjustment

• Reduce or discontinue bendroflumethiazide as thiazide diuretics have limited efficacy with eGFR <40 and may be contributing to lightheadedness 1
• Consider switching to a loop diuretic if diuretic therapy is still needed for blood pressure control 1
• Maintain losartan as it does not require dose adjustment in patients with renal impairment unless the patient is volume depleted 2, 4

2. Monitoring

• Check electrolytes (particularly potassium) as both medications can affect electrolyte balance 1, 2
• Monitor renal function within 1-2 weeks after medication changes 1, 2
• Reassess blood pressure both sitting and standing to detect any postural changes 1

3. Patient Education

• Advise the patient to rise slowly from sitting or lying positions to minimize orthostatic symptoms 1
• Instruct the patient to maintain adequate hydration but avoid excessive fluid intake 1
• Educate about symptoms that warrant immediate attention (severe dizziness, fainting, significant changes in urination) 1

Rationale for Recommendations

• Thiazide diuretics like bendroflumethiazide are less effective when eGFR falls below 30-40 mL/min/1.73 m² 1
• Loop diuretics maintain efficacy even with reduced renal function and may be more appropriate in this patient 1
• Losartan has been shown to be well-tolerated in patients with renal impairment, with pharmacokinetic studies showing no significant changes in drug exposure requiring dose adjustment 4, 5
• The ELITE II study demonstrated that losartan was well-tolerated in elderly patients with similar efficacy to ACE inhibitors but fewer adverse effects 6

Common Pitfalls to Avoid

• Don't abruptly discontinue antihypertensive medications as this can lead to rebound hypertension 1
• Avoid adding additional antihypertensive medications before addressing the current regimen's appropriateness 1
• Don't overlook the importance of monitoring electrolytes, particularly potassium, when using ARBs in patients with impaired renal function 2
• Remember that elderly patients are more sensitive to volume depletion and medication side effects 1