Concept About Furosemide – This book covers the entire syllabus of “Pharmacology” prescribed by BNMC- for diploma in nursing science & midwifery students. We tried to accommodate the latest information and topics. This book is an examination setup according to the teachers’ lectures and examination questions.
At the end of the book, previous questions are given. We hope in touch with the book students’ knowledge will be upgraded and flourish. The unique way of presentation may make your reading of the book a pleasurable experience.
Concept About Furosemide
Characteristics of high ceiling diuretics
- They are very potent (causing 15-257o of filtered sodium to be excreted).
- Progressive increase in dose is matched by increasing diuresis.
- Can act in severe renal and heart failure where other diuretics fail (effective at GFR below 10 ml/min).
- Rapid onset of action (emergency diuretic)
Mechanism of action of furosemide:
Loop diuretic (oral)
↓
Absorbed from GIT and secreted into PCT
↓
Acts on thick segment of ALLH (in the luminal membrane)
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Inhibit Na, K, 2C1 co-transport.
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Reduce NaCl reabsorption
↓ Diuresis
Pharmacological action of loop diuretics
- Inhibit Na reabsorption from thick segment of ascending limb of loop of Henle.
- Increase renal blood flow.
- Increase HCO3 excretion & along with Na+ by inhibiting carbonic anhydrase.
- Increase loos of Ca++ (hypocalcaemia) and Mg++.
- Decrease uric acid excretion (hyperuricaemia); so contraindicated in gout.
- Venodilation: Directly or indirectly through the release of a renal factor.
Indications of frusemide:
- Acute pulmonary oedema.
- Hypertensive emergency.
- Acute hypercalcaemia.
- Hyperkalaemia.
- Acute renal failure.
- Anion overdose
Clinical use of loop diuretics:
- Acute pulmonary oedema.
- Moderate hypertension.
- Left ventricular failure.
- Congestive cardiac failure (biventricular failure)
- Oedema due to liver cirrhosis.
- Oliguric phase of acute renal failure.
- Hypercalcaemia.
- Hyperkalaemia.
Contraindication of loop diuretics:
- Gout.
- Anuric renal failure.
- Pregnancy
- Hepatic cirrhosis
Adverse, effects of frusemide
- Electrolyte imbalance:
- Shisainft
- Hypokalaemia
- Hypocalcaemia
- Hypomagnesaemia
- Reversible ototoxicitv: Due to inhibition of symport mechanism in the endolymph.
- Hypovolaemia (in case of massive IV administration) associated with hypotension.
- Acid-base imbalance: Metabolic alkalosis.
- Metabolic disturbances:
- Hyperuricaemia (leading to gouty attack).
- Hyperglycaemia.
Cautions of frusemide:
- Close monitoring during Frusemide therapy.
- Assess state of dehydration
- Serum electrolytes estimation (specially K’)
- Frusemide administration with combination of K sparing diuretics
- Frusemide should administer at lower doses.
- Avoidance of simultaneous administration of other ototoxic agents
- Correction of hypovolaemia by saline infusion
- Frusemide should not use in a patient with cirrhosis of liver, borderline renal failure or heart failure.
- Monitoring of uric acid level at one-week interval
Drugs interactions:
| Interaction | Possible cause |
| Frusemide + Digoxin Digoxin toxicity develops (cardiac arrhythmia) | Furosemide causes hypokalemia.K competes with digoxin Na -K ATPase. So more action of digoxin due to less K’. |
| Frusemide + Aminoglycosides. | Pharmacological potentiation. Aminoglycosides is an ototoxic drug |
| Frusemide + cephalosporin Exacerbation of renal damage | Cephalosporin is a nephrotoxic drug. |
| Frusemide + Warfarin Anticoagulant effect of warfarin is increased. | Both drugs compete for plasma protein bound. |
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