Furosemide

Dose and administration

Intravenous and oral dosing

Intravenous infusion

Commence at 0.1 mg/kg/hour, then double the dose every 2 hours until urine output > 1 mL/kg/hour. An aggressive yet controlled diuresis is usually achieved with a dose below 0.4 mg/kg/hour. However, higher doses up to maximum of 1 mg/kg/hour have been used in infants.

Usual dilution 50 mg/kg furosemide to make 50 ml with glucose 5% or glucose 10%. 1 mL/hour = 1 mg/kg/hour.

Indications

• Fluid overload (iatrogenic, congestive heart failure, renal failure, other).

• Chronic lung disease.

• Not routinely given following blood transfusion.

Contraindications and precautions

• Contraindicated in infants with known hypersensitivity to furosemide.

• Contraindicated in infants with anuria.

• Use with caution in:

  • preterm infants, especially extreme immaturity.

  • infants with renal impairment (contraindicated in infants with renal failure due to nephrotoxic drugs).

  • infants with jaundice or at risk of hyperbilirubinemia/kernicterus.

  • infants with hyponatraemia and/or hypokalaemia, hypovolaemia or dehydration.

• Avoid concomittant use with aminoglycosides, which increases the risk of ototoxicity.

• Note that Lasix oral liquid contains 12.7% v/v ethanol (alcohol), i.e. up to 0.5 g per 5 mL of dose. Use high doses with caution in preterm infants, particularly those receiving other medications containing ethanol in whom cumulative dosing may be significant.

Clinical pharmacology

Furosemide is a potent loop diuretic with rapid action. It blocks the sodium/potassium/chloride co-transport system in the ascending limb of Henle and inhibits sodium, chloride and potassium entering the tubular cells. Increased urinary losses of potassium, calcium and phosphate (large doses only) also occur. Urine pH increases. Furosemide also increases renal blood flow.

Furosemide is rapidly absorbed from the gastrointestinal tract (bioavailability 60-70%). The half life in adults is one hour, but this is approximately 7 times greater in term neonates and at least double that in the preterm. The very preterm have furosemide half-lives of over 24 hours. It is approximately 99% bound to plasma proteins.

It is excreted mainly by the kidneys, hence the very variable half-life and extended half-life in the preterm. The proportion of active furosemide and its inactive metabolites has not been established.

Furosemide binds extensively to plasma proteins and bilirubin displacement is negligible when using normal doses of furosemide. In neonates, duration of the effect is approximately 6 hours, although half-life may be as long as 67 hours in the most immature newborn infants.

Furosemide stimulates the renal synthesis of prostaglandin E2 and early use may increase the incidence of patent ductus arteriosus.

Possible adverse effects

1. Dehydration, hypotension.

2. Gastrointestinal disturbance (oral administration).

3. Hyponatraemia, hypokalaemia, hypochloraemic metabolic alkalosis.

4. Hypercalciuria, hypocalcaemia, nephrocalcinosis.

5. Rash.

6. Ototoxicity (especially in those also receiving nephrotoxic drugs). Greater risk in the preterm and with increasing total dose.

7. Nephrotoxicity.

8. Drug accumulation, particularly with prolonged use in babies < 32 weeks gestation.

Drug interactions

Special considerations

1. Monitor sodium, potassium and chloride; monitor calcium with long term term use and pH with furosemide infusion. Electrolyte aberrations occur frequently and should be anticipated and monitored.

2. Dosing regimen determined by clinical response and infant's maturity.

3. Placement of an indwelling urinary catheter should be mandatory for infants receiving continuous infusions of furosemide.

Management of Furosemide administration

Description

IV Preparation

• Clear solution 10 mg/mL in 2 mL ampoules.

• Do not use if the solution is a yellow colour.

Oral Preparation

Lasix ® Oral Solution brand, containing frusemide 10 mg/mL in 30 mL bottles.

Note that the oral solution contains a high concentration of ethanol (12.7% v/v) i.e. up to 0.5 g per 5 mL of dose. The safety of this in children, and particularly preterm infants has not been established, and caution is advised with use.

Prescription

• Stat IV and oral doses are charted on stat page of prescription chart in mg/dose.

• Maintenance doses are charted on prescription chart in mg/dose.

Continuous infusion

Charted on fluid chart giving:

• rate in mL/hour.

• dose in mg/kg/hour.

Also charted on drug chart under "continuous infusion" giving:

• amount of drug to be added.

• type and volume of base fluid.

• note dose as mg/kg/mL.

Administration

Slow IV Injection

1. Dilution is not required.

2. Administer by slow IV injection over 5 minutes. Do not exceed 0.5 mg/kg/min or 4 mg/min, to reduce the risk of otoxicity. Filter prior to administration through a 0.2 micron Pall in-line filter.

3. Do NOT mix with other drugs, IV solution, blood or blood products.

4. Always flush with sodium chloride 0.9% after IV drug administration to prevent precipitation when mixing with drugs of low pH.

Continuous IV Infusion

1. Compatible with 0.9% sodium chloride (preferred diluent), glucose 5 % and glucose 10%

2. Administer via a syringe pump. Change fluid and tubing every 24 hours. Do not use discoloured solutions.

3. Incompatible with caffeine, dobutamine, dopamine, gentamicin and other aminoglycosides, midazolam, milrinone and morphine. Other drug compatibilities should be checked with ward pharmacist.

Nursing considerations

1. Assess for signs of adverse effects.

2. Assess IV site carefully for signs of extravasation.

3. Record weight, B.P. and pulse rate. Record urine output accurately, especially for infants on continuous infusions.

4. Measure serum electrolytes, blood glucose, SBR.

Storage