S4) Diuretics & Renal Pharmacology Flashcards
What 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 / hypokalemia
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)
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 e.g. lithium
ADH antagonists reduce concentrating ability of urine in collecting ducts
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