Oedema and diuretics

Question 1

1) state the type of oedema loop and thiazide diuretics are indicated to treat.
2) when should a combination of both these diuretics be used?

Answer 1

1) Thiazide: oedema due to chronic heart failure and in low doses to reduce blood pressure
↳Loop: used in pulmonary oedema due to left ventricular failure and in chronic heart failure
2) Combination: used in treatment of resistant oedema

Question 2

what can vigorous diuresis cause?

Answer 2

Acute hypotension - rapid reduction of plasma volume should be avoided
↳ loops more likely to cause this

Question 3

1) Thiazide and related diuretics inhibit Na+ reabsorption at the beginning of the DCT are moderately potent. state their onset and duration of action.
2) why should these drugs be taken early in the day?

Answer 3

1) Onset: Act within 1-2 hours when taken orally
↳ Duration: 12 to 24 hours
2) so that diuresis does not affect sleep

Question 4

Explain why a low dose of a thiazide is given in the management of hypertension

Answer 4

1) low doses of thiazides produce near-maximal BP lowering affect with minimal biochemical changes
2) Higher doses offer little advantage in BP control but cause marked changes in plasma: sodium, potassium, uric acid, glucose and lipids.

Question 5

name the two thiazide/thiazide related diuretics that are preferred in the management of hypertension

Answer 5

1) Indapamide

2) chlortalidone

Question 6

what conditions is bendroflumethiazide licensed to be used in?

Answer 6

1) Mild or moderate heart failure

2) Hypertension, but no longer first line

Question 7

why might chlortalidone (Thiazide-related compound) be given on alternate days to treat oedema, and why might this be beneficial?

Answer 7

1) It has a longer duration of action than the thiazides

2) useful in patients who dislike the altered pattern of micturition caused by other diuretics

Question 8

Indapamide (thiazide-like diuretic) is chemically related to chlortalidone. What are the benefits of using this drug to treat hypertension?

Answer 8

1) claimed to lower BP with less metabolic disturbance

2) less aggravation of diabetes

Question 9

which conditions can loop diuretics exacerbate in patients?

Answer 9

1) Diabetes ( but hyperglycaemia is less likely than with thiazide)
2) Gout
3) in those with enlarged prostate, urinary retention can occur, this is less likely is lower doses and when less potent diuretics are used initially.

Question 10

Furosemide and bumetanide are loop diuretics with similar activity. How long is their onset and duration of action?

Answer 10

1) Both act within 1 hour of oral administration
2) diuresis is complete within 6 hours, so they can be given BD without interfering with sleep
↳ (Diuresis associated with these drugs is dose related)

Question 11

what is the dose equivalence of bumetanide to furosemide?

Answer 11

1mg bumetanide is equivalent to 40mg furosemide

Question 12

Amiloride and triamterene (potassium sparing diuretics) are weak diuretics. why are they given with loop or thiazide diuretics?

Answer 12

They cause retention of potassium and are therefore given as an effective alternative to potassium supplements in those taking loop or thiazide diuretics

Question 13

which drugs should be used with caution along with potassium sparing diuretics? (2)

Answer 13

1) potassium supplements- these should not be given with potassium sparing diuretics/aldosterone antagonists
2) ACEi and ARBs as this can cause severe hyperkalaemia

Question 14

what is spironolactone licensed to treat?

Answer 14

1) Ooedema and ascites caused by cirrhosis of the liver
2) Low dose beneficial in moderate to severe heart failure and in resistant hypertension
2) Primary hyperaldosteronism

Question 15

what type of diuretic is mannitol and what is it indicated to treat?

Answer 15

Osmotic diuretic- used to treat cerebral oedema and raised IOP

Question 16

outline the MoA of loop diuretics

Answer 16

Inhibit reabsorption from the ascending limb of the loop of Henle by inhibiting the Na+/K+/2Cl- co-transporter
↳ powerful diuretics

Question 17

outline the important adverse effects of loop diuretics

Answer 17

1) can lead to dehydration and hypotension
2) inhibiting Na+/K+/2Cl- co-transporter increases urinary losses of ions: Na+, K+, 2Cl-, Ca2+, Mg, and metabolic alkalosis
↳ you can therefore associate loop diuretics with almost any low electrolyte state
3) at high doses hearing loss and tinnitus

Question 18

Which patients are loop diuretics contraindicated in?

Answer 18

1) Those with severe hypovolemia or dehydration
2) caution in hepatic encephalopathy as hypokalaemia can cause or worsen coma (avoided by giving K-sparing diuretics in combination)
3) avoid severe hypokalaemia and/or hyponatraemia
4) loops inhibit uric acid excretion- can worsen gout
5) renal failure due to nephro/hepatotoxic drugs

Question 19

outline the important interactions with regards to loop diuretics

Answer 19

1) potential to affect drugs excreted by the kidneys.
↳ e.g. lithium levels increase due to reduced excretion
2) Risk of digoxin toxicity due to diuretic associated hypokalaemia
3) Loops can increase the ototoxicity and nephrotoxicity of aminoglycosides

Question 20

for the following classes of diuretics give examples of drugs in each class and state their potency:

1) loop
2) Thiazide
3) Thiazide-like
4) Osmotic
5) Carbonic anhydrase inhibitor
6) potassium sparing (aldosterone antagonists)
7) potassium sparing (renal epithelial Na+ channel)

Answer 20

1) loop diuretics: Furosemide, bumetanide (high potency)
2) Thiazide: bendro, hydroxychlorthiazide (medium)
3) Thiazide-like :Indapamide ,metolazone, chlortalidone (m)
4) osmotic: mannitol, isosorbide (low potency)
5) Carbonic anhydrase inhibitor: Acetazolamide (low)
6) aldosterone antagonists: spironolactone, eplerenone (L)
7) renal epithelial Na+ channel: Amiloride (L)

Question 21

Hypokalaemia can occur with both thiazide and loop diuretics. what increases the risk of this side effect occuring

Answer 21

Risk depends on the duration of action and as well as the potency of the diuretic.
↳ risk is greater with thiazide than with loop diuretics