What is the difference between intramuscular (IM) and intravenous (IV) administration of Furosemide (Lasix)?

From the Guidelines

Lasix (furosemide) should be administered via the intravenous (IV) route rather than intramuscular (IM) administration. This recommendation is based on the most recent and highest quality study, which suggests that IV furosemide provides a faster onset of action and more predictable absorption and bioavailability compared to IM administration 1. The IV route is particularly suitable for urgent situations requiring rapid diuresis, with typical dosing starting at 20-40mg, which can be increased if needed. In contrast, IM administration is associated with pain at the injection site, variable absorption, and risk of local tissue damage, and is contraindicated in patients with bleeding disorders or those on anticoagulants.

The European Society of Cardiology guidelines recommend the use of IV diuretics, such as furosemide, for the management of patients with acute heart failure, with a recommended initial dose of 20-40mg IV 1. The guidelines also emphasize the importance of monitoring symptoms, urine output, renal function, and electrolytes during the use of IV diuretics.

In terms of dosing, the American College of Cardiology Foundation/American Heart Association guidelines provide guidance on the initial dose and maximum single dose of IV diuretic medications, including furosemide, with a recommended initial dose of 40mg and a maximum single dose of 160-200mg 1. However, the most recent and highest quality study, which is the 2016 ESC guidelines, takes precedence in guiding clinical practice 1.

Overall, the use of IV furosemide is preferred over IM administration due to its faster onset of action, more predictable absorption and bioavailability, and suitability for urgent situations requiring rapid diuresis. IV furosemide should be administered with careful monitoring of symptoms, urine output, renal function, and electrolytes, and with consideration of the patient's individual clinical status and needs.

From the FDA Drug Label

The onset of diuresis following intravenous administration is within 5 minutes and somewhat later after intramuscular administration. The peak effect occurs within the first half hour. The duration of diuretic effect is approximately 2 hours The onset of action for furosemide is faster with intravenous (IV) administration, within 5 minutes, compared to intramuscular (IM) administration.

• The peak effect of both IV and IM administration occurs within the first half hour.
• The duration of diuretic effect is approximately 2 hours for both routes of administration 2.

From the Research

Comparison of Lasix Administration Routes

• The provided studies do not directly compare the intramuscular (IM) and intravenous (IV) administration routes of Lasix (furosemide) in terms of efficacy and safety.
• However, the studies discuss the pharmacokinetics and pharmacodynamics of furosemide and other loop diuretics, which can provide some insights into the potential differences between IM and IV administration.

Pharmacokinetics of Furosemide

• The study by 3 reports that the half-life of furosemide is considerably longer in neonates than in adults, ranging from 8 to 27 hours.
• The volume of distribution of furosemide undergoes little variation during neonate maturation.
• The study by 4 discusses the pharmacodynamic concepts behind the administration of loop diuretics via continuous infusion, which may improve diuresis in critically ill patients.

Administration Routes and Diuretic Response

• The study by 3 compares continuous infusion versus intermittent infusion of furosemide and finds that diuresis is more controlled with fewer hemodynamic and electrolytic variations during continuous infusion.
• The study by 4 reviews the clinical trials and reports on the use of continuous infusion of loop diuretics in critically ill patients and finds that it may improve diuresis and reduce adverse effects.
• However, there is no direct comparison between IM and IV administration routes in these studies.

Adverse Events Associated with Loop Diuretics

• The study by 5 conducts a disproportionality analysis of adverse events associated with loop diuretics, including furosemide, torsemide, and bumetanide, using data from the FDA Adverse Event Reporting System (FAERS).
• The study identifies common and drug-specific adverse events, including electrolyte imbalances, fluid balance disorders, and nephrotoxicity, as well as novel safety signals such as vitamin B1 deficiency and Wernicke's encephalopathy associated with furosemide.
• However, the study does not specifically compare the adverse event profiles of IM and IV administration routes.