What is the recommended dosage of furosemide (Lasix) for a patient with hypertension (High Blood Pressure) and Left Bundle Branch Block (LBBB)?

Furosemide Dosing in Hypertension with LBBB

For a hypertensive patient with LBBB who has evidence of fluid overload, start furosemide 40 mg orally twice daily (morning and early afternoon), titrating every 3-5 days based on blood pressure response and weight loss, with a maximum of 160 mg/day total—but furosemide must never be used as monotherapy for hypertension and should always be combined with ACE inhibitors, ARBs, or beta-blockers for long-term blood pressure control. 1, 2

Critical Context: LBBB Does Not Alter Furosemide Dosing

The presence of LBBB is not a contraindication to furosemide use and does not require dose modification. 3 LBBB is an electrical conduction abnormality that does not affect diuretic pharmacokinetics or response. The dosing strategy should focus entirely on the hypertension and any concurrent fluid overload status.

Initial Dosing Strategy

For Hypertension Without Significant Fluid Overload

• Start with 40 mg orally twice daily (total 80 mg/day), as the FDA label recommends 80 mg for hypertension, usually divided into 40 mg twice daily. 2
• Twice-daily dosing is superior to once-daily because furosemide's duration of action is only 6-8 hours, leaving 16-18 hours without active diuretic effect with single dosing. 1

For Hypertension With Concurrent Fluid Overload

• Start with 40 mg orally twice daily if there is evidence of peripheral edema, pulmonary congestion, or jugular venous distension. 1
• Loop diuretics like furosemide are the cornerstone when hypertension coexists with volume overload. 1

Dose Titration Protocol

• Adjust doses every 3-5 days if blood pressure reduction is inadequate, targeting systolic BP <140 mmHg and diastolic BP <90 mmHg. 1, 3
• Increase by 20-40 mg increments per dose (e.g., from 40 mg BID to 60 mg BID), not exceeding 160 mg/day total for chronic hypertension management. 2, 1
• If blood pressure remains uncontrolled despite 160 mg/day furosemide, add thiazide diuretics or aldosterone antagonists for synergistic effect rather than escalating furosemide further. 1, 3

Mandatory Concurrent Antihypertensive Therapy

Furosemide should never be used as monotherapy for hypertension. 1 Always combine with:

• ACE inhibitors or ARBs as first-line agents for long-term blood pressure control. 3, 1
• Beta-blockers may be particularly appropriate given the LBBB, as they reduce cardiovascular risk. 3
• When adding furosemide to existing antihypertensive regimens, reduce the dose of other agents by at least 50% initially to prevent excessive blood pressure drop. 2

Critical Monitoring Requirements

Initial Phase (First 2-4 Weeks)

• Daily weights at the same time each day, targeting 0.5-1.0 kg loss per day if fluid overload present. 1
• Blood pressure monitoring every 3-7 days during dose titration. 1
• Serum electrolytes (potassium, sodium) and renal function every 3-7 days initially, as furosemide commonly causes hypokalemia and hyponatremia. 1, 3

Maintenance Phase

• Check electrolytes and renal function every 3-4 months once stable. 4
• Monitor for orthostatic hypotension, particularly in elderly patients, by checking supine and standing blood pressures. 1

Absolute Contraindications and When to Stop

• Do not start furosemide if systolic BP <90 mmHg, marked hypovolemia, severe hyponatremia (Na <120-125 mmol/L), or anuria. 4, 3
• Stop furosemide immediately if severe hyponatremia, progressive renal failure, marked hypotension, or anuria develops. 4, 3

Common Pitfalls to Avoid

• Do not use furosemide in hypotensive patients expecting it to improve hemodynamics—it will worsen hypoperfusion. 1
• Avoid NSAIDs during furosemide therapy, as they block diuretic effects and increase risk of renal insufficiency. 1
• Do not give evening doses of furosemide, as they cause nocturia and poor adherence without improving outcomes. 4
• Starting with once-daily dosing is suboptimal due to the short 6-8 hour duration of action. 1

Dietary and Lifestyle Modifications

• Restrict dietary sodium to <2-3 g/day to maximize diuretic efficacy and reduce required doses. 1, 3
• This sodium restriction is critical for achieving blood pressure targets and may allow lower furosemide doses. 1

Special Considerations for Chronic Kidney Disease

If the patient has concurrent CKD (which is common with hypertension), substantially higher doses may be required due to reduced drug delivery to tubular sites of action. 1 However, the maximum of 160 mg/day for chronic hypertension management should still be respected, with combination therapy preferred over further escalation. 1, 4

Route of Administration

Oral administration is strongly preferred for chronic hypertension management due to convenience and adequate bioavailability in stable patients. 1 IV furosemide is reserved for acute hypertensive emergencies with pulmonary edema or severe volume overload requiring rapid diuresis. 4