S4) Diuretics & Renal Pharmacology Flashcards
yWhat are the four broad functions of the kidney?
- Regulatory
- Excretory
- Endocrine
- Metabolism
What are the three regulatory functions of the kidney?
- Fluid balance
- Acid-base balance
- Electrolyte Balance
What does the kidney excrete?
- Waste products
- Drug elimination (glomerular filtration & tubular secretion)
Identify four endocrine secretions of the kidney
- Renin
- Erythropoetin
- Prostaglandins
- 1-alpha calcidol
Which substances does the kidney metabolise?
- Vitamin D
- Polypeptides e.g. insulin
- Drugs e.g. morphine, paracetamol
What are the seven different types of diuretic drugs acting on the kidney?
- Carbonic anhydrase inhibitors
- Osmotic diuretics
- Loop diuretics
- Thiazides
- K+ sparing diuretics
- Aldosterone antagonists
- ADH Antagonists
Describe the actions and effects of carbonic anhydrase inhibitors
- Sodium bicarbonate diuresis
- Excretion of Na+, K+ and PO3
- Metabolic acidosis (loss of bicarbonate) / hypokalemia (lose K at RomK channels)
Describe the actions and effects of osmotic agents
- Filtered at glomerulus
- Increase osmotic gradient throughout nephron
- Excessive water loss
- Hypernatraemia
Describe the actions and effects of loop agents
- Thick ascending limb loop of Henle
- Inhibit NaCl reabsorption
- Concurrent Ca/Mg excretion
- Hypokalaemia (CD) because there is an increase in the activation of RomK to increase Enac so more K leaves
- causes direct dialation of veins that reduce preload
Describe the actions and effects of thiazides
- Inhibits NaCl reabsorption
- Promotes Ca reabsorption
- Hypokalaemia
- Hyperuricaemia
Describe the actions and effects of aldosterone antagonists e.g. spironolactone
- Inhibits Na+ retention (Na-K ATPase / Na+ flux)
- Blunts K+ and H+ secretion
- Androgenic cross-reactivity
What is the action of aldosterone on the kidney
Aldosterone increases expression of ENaC and Na/K/ATPase in principal cells of the collecting duct
Describe the actions and effects of ADH antagonists ‘ aquaretics’ e.g. lithium
ADH antagonists reduce concentrating ability of urine in collecting ducts
- tolvaptan → diuretic but not natriuretic, treat hyponatremia
- lithium → diuretic not a natriuretic
Explain how the following substances have diuretic action:
- Alcohol
- Caffeine
- Alcohol – inhibits ADH release
- Caffeine – ↑GFR and ↓ tubular Na+ reabsorption
Identify four generic adverse drug reactions from diuretics
- Anaphylaxis / photosensivity rash
- Hypovolaemia & hypotension
- Electrolyte disturbance (Na+, K+, Mg2+, Ca2+)
- Metabolic abnormalities
Identify 5 common specific ADRs from thiazides
- Gout
- Hyperglycaemia
- Erectile dysfunction
- ↑LDL & TG
- Hypercalcaemia
Identify 3 common specific ADRs from spironolactone
- Hyperkalaemia
- Impotence
- Painful gynaecomastia
Identify 4 common specific ADRs from furosemide (loop diuretic)
- Ototoxicity
- Alkalosis
- ↑LDL & TG
- Gout