FRUSEMIDE

“LASIX’

1) Action Most powerful of all clinically used diuretics

Short acting agents

2) Mechanism

Inhibit Na⁺ and Cl^- reabsorption in the thick ascending limb of the loop of Henle via Na+, K+, -ATPase-dependent pump —>

i) increased solute load in distal portions of nephron —> act as osmotic agents

ii) failure to reabsorb Na+ & Cl- at loop of Henle —> decreased osmolarity in medullary interstitial fluid —> reduced concentrating ability of kidney

Owing to the large NaCl absorptive capacity of the loop of Henle, agents that act at this site produce a diuretic effect much greater than that seen with other diuretic groups

3) Indications Pulmonary & cerebral oedema

Hypertension

Renal protection during CPB [reverses effect of CPB on renal blood flow resulting in increased creatinine clearance]

May benefit oliguric or anuric patients

4) Effects on organs—side effects

The thick ascending limb of the loop of Henle plays an important part in divalent cation handling; inhibition of active NaCl transport —> increased Ca²⁺ and Mg²⁺ excretion: —> hypomagnesemia & hypocalcaemia [useful for acute hypercalcemia]

Due to increased Na⁺ to more distal segments of nephron —> exchange of Na⁺ for H⁺ and K⁺ —> metabolic alkalosis and hypokalemia

5) Toxic effects/ precautions with administration

Disturbances in electrolyte & water balance

6) Contraindications

7) Reversal, antagonism or antidote

8) Loading dose, maintenance dose, frequency & method of administration

Ampuoles: 20 mg/2 ml

9) Drug’s metabolism—Drug’s excretion—Half life (pharmacokinetics)

Fast response post IV injection; lasts 2-3 hours

10) Important drug interactions

The renal protective effects of lasix & low dose dopamine are synergistic