Loop diuretics

Question 1

What are some examples of Loop diuretics

Answer 1

• Furosemide, bumetanide

Question 2

What are the indications for use

Answer 2

• Acute pulmonary oedema (relieve breathlessness, in conj w/ O2 + nitrates)
• Chronic HF (symptomatic for fluid overload)
• symptomatic Tx for fluid overload in other oedematous states (e.g. renal/liver disease)

Question 3

What is the mechanism of action for loop diuretics

Answer 3

• Act on ascending limb of Loop of Henle
• Inhibit Na+/K+/2Cl- co-transporter (transports ions into epithelial cells from tubular lumen –> Water follows by osmosis)
• Inhibiting = diuretic effect
• Causes dilation of capacitance veins –> reduced preload + improves contractile function (acute heart failure)

Question 4

What are the side effects

Answer 4

• Dehydration
• Hypotension (water loss)
• low electrolytes state (loss of Na, K, Cl which –> excretion Mg, Ca, H+)
• Hearing loss/ tinnitus (co-transporter in inner ear –> regulate endolymph)

Question 5

What are the contra-indications

Answer 5

• Hypovolaemia
• Dehydration
• CAUTION - hepatic encephalopathy risk
• Hypokalasemia/natraemia
• Gout (inhibit uric acid secretion)

Question 6

What are the interactions

Answer 6

• Affects drugs that are excreted by kidneys
  e. g. lithium (++ due to – excretion)
  e. g. digoxin toxicity
  e. g. aminoglycosides (increase ototoxicity + nephrotoxicity)