What is the oral equivalent of IV Lasix (furosemide) 80mg twice daily for discharge?

Converting IV Furosemide 80mg BID to Oral for Discharge

For a patient on IV furosemide 80mg twice daily, convert to oral furosemide 160mg twice daily (total 320mg/day) for discharge. 1, 2

Conversion Rationale

The standard approach is to double the IV dose when converting to oral due to furosemide's approximately 50% oral bioavailability 1, 3. Since your patient is receiving 80mg IV twice daily (160mg total daily IV dose), the equivalent oral dose is 160mg twice daily (320mg total daily oral dose).

Key Pharmacokinetic Principles

• Oral bioavailability of furosemide is highly variable (10-90%), averaging around 50% in heart failure patients due to gut edema and impaired absorption 1, 3
• IV administration provides more rapid onset but oral is preferred for chronic management once the patient is stabilized and decongested 1
• Response correlates with urinary drug concentration, not plasma levels, so adequate dosing is critical to maintain therapeutic effect 3

Practical Discharge Dosing Strategy

Standard Conversion

• Start with oral furosemide 160mg twice daily (at 8am and 2pm dosing intervals) 2
• This maintains the same total daily furosemide equivalent as the IV regimen 4

Important Caveats

Twice-daily dosing is superior to once-daily for furosemide due to its short duration of action (6-8 hours), preventing post-diuretic sodium retention between doses 5. The FDA label specifically recommends dosing intervals of 6-8 hours when needed 2.

Monitor closely in the first week post-discharge as oral absorption may be unpredictable, particularly if residual congestion or gut edema persists 1, 3. Consider a follow-up within 3-7 days to assess volume status and adjust dosing.

When Higher Doses May Be Needed

If the patient has advanced heart failure requiring furosemide equivalents >160mg/day, they fall into the category of advanced disease 4. In such cases:

• Doses up to 600mg/day oral furosemide may be carefully titrated with close monitoring 2
• Consider adding a thiazide diuretic (sequential nephron blockade) if resistance develops rather than escalating loop diuretic doses indefinitely 4

Red Flags for Inadequate Conversion

Watch for signs of under-diuresis after conversion:

• Weight gain >2-3 lbs in 24-48 hours 4
• Recurrent dyspnea or orthopnea 4
• Peripheral edema worsening 4

If these occur, the oral dose may need to be increased beyond the 2:1 conversion ratio due to individual variability in absorption 1, 3.