View source for Loop diuretic

== Background ==
* Mechanism: Inhibits Na-K-2Cl carrier in the '''thick ascending Loop of Henle'''^1^
* Potency: Highest among diuretic classes
* '''Adverse Effects'''
** Hypokalemia (most common)
** Hypomagnesemia, hyponatremia, hypocalcemia
** Ototoxicity (associated with rapid IV push)
** Pre-renal [[Acute Kidney Injury|AKI]] (due to over-diuresis)
* '''Sulfa Allergy:''' Most are sulfonamide derivatives; cross-reactivity is rare but possible

== Key Agents ==
* '''[[Furosemide]]''' (Lasix)
** '''Bioavailability:''' Highly variable PO absorption (10-90%, avg ~50%)
*** IV dose is approx 2x as potent as PO dose (e.g., 20mg IV ≈ 40mg PO)
** '''Dosing:''' In [[CHF]], usually start with 1-2.5x the patient's daily home dose IV

* '''[[Has Diuretic::Bumetanide]]''' (Bumex)
** '''Potency:''' ~40x more potent than furosemide
*** 1 mg Bumetanide ≈ 40 mg Furosemide
** '''Bioavailability:''' High and reliable absorption (>80%)
** Often reserved for patients refractory to furosemide or with severe gut edema

* '''[[Has Diuretic::Torsemide]]''' (Demadex)
** '''Kinetics:''' Longer half-life than furosemide
** '''Bioavailability:''' Excellent oral absorption
*** PO dose is essentially equivalent to IV dose
** Less common in acute resuscitation; helpful for chronic management

* '''[[Has Diuretic::Ethacrynic acid]]''' (Edecrin)
** '''Class:''' Phenoxyacetic acid derivative (not a sulfonamide)
** '''Indication:''' The only alternative for patients with ''severe'' or anaphylactic '''sulfa allergy'''
** '''Toxicity:''' Highest risk of ototoxicity among loop diuretics
** Seldom used as first-line due to side effect profile

== See Also ==
* [[Heart Failure]]
* [[Pulmonary Edema]]
* [[Diuretics]]

== References ==
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[[Category:Pharmacology]][[Category:Cardiology]][[Category:Renal]]