Diuretics & renal drugs

Question 1

How does Acetazdamide work as a diuretic?

Answer 1

Carbonic anhydrase inhibitor- inhibits HCO3- breakdown to H20 and CO2 to less HCO3- reabsorbtion so less H20 reaborbtion

Question 2

Name one osmotic diuretic

Answer 2

Mannitol

Question 3

How does amilloride work

Answer 3

Inhibits ENaC in DCT and also NHE in proximal tubule (minor effect), so less sodium and so less water reaborption

Question 4

Name one loop diuretic and the channel it acts on?

Answer 4

Furosemide acts on NKCC

Question 5

Name 2 thiazide diuretics

Answer 5

Chlorothiazide, indapamine, bendroflumethiazide

Question 6

Name 2 ADH antagonists

Answer 6

Tolvaptan and lithium, others in caffine and alcohol

Question 7

How does bumetanide work?

Answer 7

Loop diuretic- inhibits NCCK, is more potent than furosemide

Question 8

How do ADH antagonists act? When are they used?

Answer 8

Inhibit ADH, so less opening of AQP in distal tubules, so less water reabsorbed. Used in treatment of hyponaturaemia as cause water excretion but not sodium excretion.

Question 9

Give 3 general ADRs of diuretics

Answer 9

• anaphylaxis
• hypovolaemia leading to hypotension (AKI)
• electrolyte disturbances (k+, Mg+, Na+, Ca2+)
• some metabolic disturbances

Question 10

Give 3 ADRs specific to loop diuretics

Answer 10

• Gout
• Hypokalaemia an alkalosis
• ototoxic in large quantities
• increased LDL and TAG

Question 11

Give 3 ADRs specific to thiazide diuretics

Answer 11

• Gout
• hypokalaemia and akalosis
• erectile dysfunction
• hypercalcaemia
• hyperglyacemia (reduced insulin sensitivity)

Question 12

give 3 ADRs specific to spironolactone

Answer 12

• hyperkalaemia–> acidosis
• impotence
• painful breast tissue enlargement in men

Question 13

Describe the consequence of prescribing an ACEi and a K+ sparing diuretic like amiloride

Answer 13

Both will decrease K+ excretion leading to hyperkalaemia and so cardiac problems

Question 14

Describe the consequence of prescribing digoxin and a thiazide or loop diuretic

Answer 14

Diuretic leads to hypokalaemia, this leads to increased digoxin binding and toxicity, which in turn leads to cardiac problems

Question 15

What is the risk of prescribing Loop/ thiazide diruetics with steroids?

Answer 15

Both will increase risk of hypokalaemia, due to steroids mineralocorticoid effect to up regulate ENaC and so increase ROMK activity and the diuretics effect to increase distal salt delivery.

Question 16

Give 5 uses for diuretics, and state the type of diuretic most commonly indicated

Answer 16

• Hypertension (usually thiazide as has additional vasodilatory properties)
• Heart failure (usually loop diuretics as are most powerful so clear odema well, spironolactone indicated for benefits in heart remodelling)
• decompensated liver disease (spironolocatone or loop to clear ascites, hypertension etc)
• Nephrotic syndrome (loop + others to reduce odema caused by albumin loss)
• CKD (loop +/- thiazide beneficial to clear fluid retention as well as prevent hyperkalaemia due to poorer removal of K+)

Question 17

Why may diuretics not work very well in nephrotic syndrome

Answer 17

• odema in gut means less absorbtion of drug (may need IV)
• less albumin in drug reduces its half life
• If renal failure- poorer reuptake of drug so just piss it out

Question 18

What dietary factor may reduce diuretic action?

Answer 18

high salt diet- offsets extra Na+ losses from diuretic

Question 19

Give 3 nephrotoxic drugs

Answer 19

aminoglycosides, vancomycin, aciclovir, NSAIDS, many/ most drugs

Question 20

Give 2 common drugs which may worsen GFR?

Answer 20

• ACEi and ARB–> Angiotensin 2 needed for efferent vasoconstriction, less of this= less GFR
• NSAIDS–> prosaglandins important in afferent vasodilation, this is inhibited= less GFR

Question 21

Give 3 causes of hyperkalaemia

Answer 21

• Acidosis or muscle damage causing release from cells
• reduced GFR (AKI), increased distal Na+ delivery (diuretics)
• Drugs (ACEi, Spironolactone, ARB, NSAIDS, amiloride, trimethoprim)

Question 22

Describe the signs and symptoms of hyperkalaemia

Answer 22

• tiredness or weakness
• numbness and tingling
• N+V
• trouble breathing
• chest pain
• palpitations

Question 23

Describe the ECG changes of hyperkalaemia

Answer 23

• 1st sign = tall tented T waves, prolonged PR
• 2nd= ST elevation, loss of P wave, widened QRS, ectopic beats
• 3rd= QRS widens more and peaks lower, T wave widens until just looks like 3 large waves, leads to V. fib, asytole

Question 24

How would you treat hyperkalaemia (3)

Answer 24

• give calcium gluconate to protect heart
• Give insulin and dextrose to lower serum K+
• give calcium resonuim or thiazide/ loop diuretic to increase K+ removal
• Can also give salbutamol if no insulin and dextrose, rarely NaCO3 will be given for acidosis