Diuretics Flashcards
What are the types of diuretics?
- Loop
- Thiazide
- K+ Sparing (Aldosterone antagonists)
- Osmotic diuretics
- Carbonic anhydrase inhibitors
Give 2 examples of loop diuretics
- Furosemide
- Butemanide
What is the mechanism of action of loop diuretics?
Inhibits Na/K/2Cl co-transporter in the loop of Henle
Give an example of a thiazide diuretics
Bendoflumethiazide
What is the mechanism of action of thiazide diuretics?
Inhibits Na/Cl co-transporter in DCT
How long do thiazide diuretics take to have effect?
1-2 hours
What is the duration of action of thiazide diuretics?
Up to 24 hours
What are aldosterone antagonists also known as?
Potassium sparing diuretics
Give 2 examples of aldosterone antagonists
- Spironolactone
- Amiloride
What is the mechanism of action of aldosterone antagonists?
Prevent reabsorption of Na in the DCT, thus causing Na and H2O excretion and K retention
Give an example of an osmotic diuretic
Mannitol
What is the mechanism of action of osmotic diuretics?
Causes reabsorption of H2O in the PCT and the descending limb of the loop of Henle, and opposes the action of ADH in the collecting duct
Give an example of a carbonic anhydrase inhibitor
Acetazolamide
What is the mechanism of action of carbonic anhydrase inhibitors?
Block carbonic anhydrase at the PCT, so bicarbonate cannot be reabsorbed and is retained in the PCT with H2O and Na
What are the routes of delivery of diuretics?
- PO
- IV
- Topical
What are the indications for loop diuretics?
- Acute pulmonary oedema and chronic heart failure
- Oliguric renal insufficiency
What are the indications for thiazide/thiazide-like diuretics?
- Hypertension
- Nephrogenic diabetes
What are the indications for potassium-sparing diuretics?
- Hypertension
- Hypokalaemia
- Ascites and oedema secondary to hepatic cirrhosis
What are the indications for osmotic diuretics?
- Cerebral oedema
- Raised intraocular pressure
- Treatment of cystic fibrosis
What are the indications for carbonic anhydrase inhibitors?
Glaucoma
What is the role of loop diuretics in heart failure?
They provide symptomatic improvement but do not reduce mortality in heart failure
Describe the use of diuretics in the elderly?
Should be used with caution, and at the lowest dose possible
Why should diuretics be used with caution in the elderly?
Because they are particularly susceptible to side effects
Can diuretics be used in pregnancy?
Should be avoided due to risk of volume depletion
When should loop diuretics be used with caution?
- Hypovolaemia
- Hypotension
- Prostatic hypertrophy
- History of diabetes or gout
When should loop diuretics be avoided?
- Anuria
- Severe hyponatraemia
- Severe hypokalaemia
- Comatose or pre-comatose states associated with liver cirrhosis
When should thiazide diuretics be used with caution?
- Malnutrition
- Renal impairment
- Patients with history of gout or diabetes
When should thiazide diuretics be avoided?
- Addison’s disease
- Symptomatic hyperuricaemia
- Refractory hyponatraemia
When should potassium-sparing diuretics be used with caution?
Renal impairment (avoid if severe)
When should potassium-sparing diuretics be avoided?
- Hyperkalaemia
- Hyponatraemia
- Anuria
- Addison’s disease
When should osmotic diuretics be used with caution?
Asthma and haemoptysis, if given by inhaled route
When should osmotic diuretics be avoided?
- Anuria
- Acute intracranial bleeding (except in craniotomy)
- Severe heart failure
- Severe pulmonary oedema
When should osmotic diuretics given by inhalation be avoided?
- Impaired lung function
- Patients who are hyperresponsive to mannitol
Who should carbonic anhydrase inhibitors be used with caution in?
- Eldery
- Diabetic
- Patients with renal calculi
- Those with impaired alveolar ventilation
Who should carbonic anhydrase inhibitors be avoided in?
- Adrenocortical insufficiency
- Hypochloraemic acidosis
- Hypokalaemia
- Hyponatraemia
- Chronic angle-closure glaucoma (long-term use)
What interactions are common to loop diuretics, thiazides/thiazide-like diuretics, and potassium-sparing diuretics?
- Drugs affecting RAAS system
- Anti-hypertensive drugs
- NSAIDs
- Lithium
What drugs affect the RAAS system?
- ACE inhibitors
- ARBs
- Direct renin inhibitors
What might happen if diuretics are given with drugs affecting the RAAS system?
Increased risk of hyperkalaemia
What might happen if diuretics are given with anti-hypertensive drugs?
Increased hypotensive effect
What might happen if diuretics are given with NSAIDs?
Increased risk of nephrotoxicity
What might happen if diuretics are given with lithium?
Increased risk of lithium toxicity
What drug should not be given with potassium-sparing diuretics?
K supplements
Why should K supplements not be given with potassium-sparing diuretics?
Increased risk of hyperkalaemia
What drug might mannitol interact with?
Ciclosporin
What might happen if mannitol is given with ciclosporin?
Increased risk of nephrotoxicity
What drugs might interact with carbonic anhydrase inhibitors?
- Phenytoin
- Phenobarbital
What might happen if carbonic anhydrase inhibitors are given with phenytoin or phenobarbital?
Increased risk of osteomalacia
What drugs might interact with acetazolamide?
- Aminophylline
- Amiodarone
What might happen if acetazolamide is given with aminophylline?
Increases risk of hypokalaemia
What might happen if azetazolamide is given with amiodarone?
Hypokalaemia induced by acetazolamide increases the risk of cardiac toxicity with amiodarone
What monitoring is required with diuretics?
- Monitor fluid and electrolyte balance and serum osmolality, and review cardiac, pulmonary, and renal function
- Monitor serum potassium level during treatment
- Consider measuring daily weights in patients using diuretics for relief of fluid overload
What should you do if hyperkalaemia occurs with diuretic treatment?
Discontinue treatment
What are the side effects of loop diuretics?
- Hypokalaemia
- Hyponatraemia
- Ototoxicity
- Hyperuricaemia
- Acute urinary retention
What can high doses or rapid IV administration of furosemide cause?
Tinnitus or deafness
What are the side effects of thiazide/thiazide-like diuretics?
- Hypokalaemia
- Altered blood lipids
- Postural hypotension
- Impotence
- May precipitate gout attacks and increase the risk of pancreatitis
What are the side effects of potassium sparing diuretics?
- GI disturbances
- Acute renal failure
- Hyperkalaemia
- Hyponatraemia
- Gynaecomastia
- Hypogonadism
- Menstrual irregularities in women
- Impotence in men
What are the side effects of inhaled osmotic diuretics?
- Cough
- Bronchospasm
- Wheezing
- Haematoptysis
- Irritation and pain in throat
- Vomiting
What are the side effects of IV osmotic diuretics?
- Electrolyte and fluid imbalance
- Hypotension
- Thrombophlebitis
What are the side effects of carbonic anhydrase inhibitors?
- Ataxia
- Dizziness
- Changes in mood and libido
- Nausea
- Loss of appetite
- Taste disturbance
- Thirst
What counselling is required with diuretics?
- Frequency and nocturia
- Compliance with monitoring
- Reduced dietary intake of salt
What counselling is required regarding frequency and nocturne with diuretics?
Inform patient that the drug will make them pass more urine and it is advisable to take doses during the day to prevent nocturia
What counselling is required regarding compliance with monitoring with diuretics?
Emphasise importance of blood tests to detect harmful electrolyte imbalances to enable treatment
What counselling specific to potassium sparing diuretics is required?
The patient should take this drug with or after food, and should not take potassium supplements whilst taking this drug.
Not advisable to take NSAIDs, such as ibuprofen, when taking this medication If the patient becomes unwell with vomiting and diarrhoea, they should stop taking the drug to prevent dehydration and contact their doctor for further management
