'''Loop diuretics''' are [[diuretic]]s that act on the ascending [[loop of Henle]] in the [[kidney]]. They are primarily used in [[medicine]] to treat [[hypertension]] and [[edema]] often due to [[congestive heart failure]] or [[renal insufficiency]].
== Mechanism of action ==
Loop diuretics act on the [[sodium|Na]]<sup>+</sup>/[[potassium|K]]<sup>+</sup>/[[chloride|Cl]]<sup>-</sup> cotransporter in the ascending loop of Henle to inhibit sodium and chloride reabsorption. Because [[magnesium]] and [[calcium]] reabsorption in the thick ascending loop is dependent on sodium and chloride concentrations, loop diuretics also inhibit their reabsorption. This raises the [[osmotic pressure]] inside the loop, driving more water into the filtrate causing increased [[urine]] volume.
Loop diuretics also cause [[vasodilation]] of the [[vein]]s and of the kidney's [[blood vessel]]s, mechanically causing a decrease in [[blood pressure]].
The collective effects of increased urine production and vasodilation decrease blood pressure and ameliorate edema.
==Clinical use==
Loop diuretics are principally used in the following indications (Rossi, 2004):
* edema associated with [[heart failure]], hepatic [[cirrhosis]], [[renal impairment]], [[nephrotic syndrome]]
* [[hypertension]]
* adjunct in [[cerebral edema|cerebral]]/[[pulmonary edema]] where rapid [[diuresis]] is required ([[intravenous|IV]] injection)
They are also sometimes used in the management of severe [[hypercalcemia]] in combination with adequate rehydration (Rossi, 2004).
== Loop diuretic resistance ==
Renal insufficiency causes decreased bloodflow to the kidneys, which decreases the [[glomerular filtration rate]] (GFR) and reduces the ability of loop diuretics to reach their target organ, the loop of Henle. Similarly, [[non-steroidal anti-inflammatory drug]]s also decrease GFR with comparable results. In patients with reduced GFR, ceiling dosages of loop diuretics are increased proportional to the decrease in GFR. Simultaneous treatment with a [[thiazide]] diuretic such as [[hydrochlorothiazide]] (to inhibit sodium reabsorption at multiple sites in the nephron) is often successful.
Patients with congestive heart failure tend to retain sodium, also necessitating an increase in dosage. The same is true for patients with increased sodium intake.
== Adverse effects ==
The most common adverse drug reactions (ADRs) are dose-related and relate to the effect of loop diuretics on diuresis and [[electrolyte]] balance.
Common ADRs include: [[hyponatremia]], [[hypokalemia]], [[hypomagnesemia]], [[dehydration]], [[hyperuricemia]], [[gout]], [[dizziness]], [[postural hypotension]], [[syncope]] (Rossi, 2004).
Infrequent ADRs include: [[dyslipidemia]], increased serum [[creatinine]] concentration, hypocalcemia, [[rash]] (Rossi, 2004).
[[Ototoxicity]] (damage to the [[ear]]) is a serious, but rare ADR associated with use of loop diuretics. This may be limited to [[tinnitus]] and [[vertigo]], but may result in [[deafness]] in serious cases.
Loop diuretics may also precipitate renal failure in patients concomitantly taking an [[NSAID]] and an [[ACE inhibitor]] -- the so-called "triple whammy" effect (Thomas, 2000).
== Examples of loop diuretics ==
* [[Furosemide]]
* [[Bumetanide]]
* [[Ethacrynic acid]]
==References==
* Rossi S (Ed.) (2004). ''[[Australian Medicines Handbook]] 2004''. Adelaide: Australian Medicines Handbook. ISBN 0-9578521-4-2.
* Thomas, MC (2000). Diuretics, ACE inhibitors and NSAIDs -- the triple whammy. ''Med J Aust'' '''172''', 184–185. PMID 10772593
== External links ==
* [http://www.fpnotebook.com/CV222.htm Loop Diuretic], from the Family Practice Notebook
[[Category:Diuretics]]
[[fr:Diurétique de l'anse]]
This site is not affiliated with or endorsed in any way by the Wikimedia Foundation or any of its affiliates. In fact, we fucking despise them.
|
