DIURETICS-LOOP DIURETICS

SUMMARY

1. They remain effective when GFR is low (CrCl < 20 cc/min), but you have to increase the dose and/or give IV. Quite powerful: excretion of 20 to 25% of filtered sodium.

2. Inhibit the Na⁺/2CI^-/K⁺ co-transporter & prevent reabsorption of Na⁺ in the thick ascending segment of Loop of Henle.

3. Hence, prevents development of the interstitial osmotic gradient, relied upon by the thin descending segment for water reabsorption.

4. The net effect is loss of both Na⁺ & water.

5. K⁺ is co-transported by the pump that is inhibited by loop diuretics, leading to hypokalemia.

6. Loop diuretics also increase Ca⁺ loss in the urine. Potential concern of nephrocalcinosis.

Reference(s)

Wilkinson, I., Furmedge, D. and Sinharay, R. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press. Get it on Amazon.
Feather, A., Randall, D. and Waterhouse, M. (2020). Kumar And Clark’s Clinical Medicine. 10th ed. S.L.: Elsevier Health Sciences. Get it on Amazon.
Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
Therapeutic Guidelines. Melbourne: Therapeutic Guidelines Limited. https://www.tg.org.au [Accessed 2021].