What is the equivalent oral dose of Bumex (bumetanide) when converting from an IV dose in a patient with potential impaired renal function?

Bumetanide IV to Oral Dose Conversion

The oral dose of bumetanide is equivalent to the IV dose on a 1:1 milligram basis, meaning 1 mg IV = 1 mg oral. 1

Bioavailability and Absorption

• Bumetanide has approximately 80% oral bioavailability, which is substantially higher than furosemide's 40% bioavailability 2
• The drug is rapidly and almost completely absorbed after oral administration, with peak plasma levels achieved within 30 minutes 3, 4
• Because of this high bioavailability, oral and parenteral formulations have similar pharmacokinetic profiles, allowing for straightforward 1:1 dose conversion 4

Standard Dosing Ranges

Oral dosing:

• Initial dose: 0.5 to 1.0 mg once or twice daily 1
• Maximum total daily dose: 10 mg 1
• Duration of action: 4 to 6 hours 1

IV/IM dosing:

• Initial dose: 1-2 mg/kg (usual maximum 20 mg for patients not chronically on loop diuretics) 1
• For adults with heart failure: typically 0.5 to 2 mg/day produces comparable results to furosemide 20 to 80 mg/day 3

Potency Comparison to Furosemide

• Bumetanide is approximately 40-50 times more potent than furosemide on a milligram basis 3, 5, 2, 6
• The conversion ratio is approximately 1 mg bumetanide = 40 mg furosemide 3, 5
• However, for IV to oral conversion within the same drug (bumetanide), the ratio remains 1:1 due to high bioavailability 2

Renal Impairment Considerations

• Higher doses may be required (up to 15 mg/day) in patients with chronic renal failure or nephrotic syndrome 3
• Bumetanide remains effective even when modest to severe renal insufficiency is present 4
• Patients with renal disease may actually respond better to bumetanide than furosemide at equivalent doses 3
• Glomerular filtration rates are generally unaffected by bumetanide therapy 3

Clinical Pearls and Caveats

• The time course of diuretic response is identical between IV and oral routes, with oral dosing producing peak effect at 75 minutes versus 30 minutes for IV 5
• Muscle cramps are not uncommon in patients with renal failure receiving bumetanide, particularly at higher doses 3
• The incidence of hypochloremia and hypokalemia is greater with bumetanide compared to furosemide 6
• Bumetanide has a lower potential for ototoxicity compared to furosemide, making it preferable in patients at increased risk 3, 6