Drugs and the kidneys Flashcards
Thiazide and thiazide related diuretics
Action takes place in the distal convoluted tube
Block the chloride pump on apical membrane therefore electrolytes can’t be reabsorbed back into the circulation
Increased conc. in tubule therefore increased water
Increased excretion of sodium and chloride in urine (urine flow rate increased from 1 to 3ml/min)
Also increases the excretion of potassium
eg. Bendroflumethazide (thiazide), Metolazone, Indapamide (related)
5-10% filtered sodium excreted
Take in the morning, last 24 hours, act in 1-2 hours
Side effects: hypokalaemia (dizziness), hypocalcaemia (muscle fatigue), hyperuricemia (gout), hyperglycaemia (diabetes)
Loop diuretics
Action takes place on the Loop of Henle
Blocks the sodium/potassium/chloride pump so can’t be reabsorbed into the circulation
Increase conc. in tubule therefore increased water
Increased excretion of all of these in the urine
eg. Furosemide, Bumetanide
Up to 30% filtered sodium excreted (very powerful)
Urine flow rate increases from 1 to 8ml/min
Side effects: hypokalaemia, hypocalcaemia, hyperuricemia, hyperglycaemia, deafness
Potassium sparing diuretics
Action takes place on the late distal tube and the collecting duct
Increase sodium, water excretion chloride and calcium
Decrease excretion of potassium and H+
eg. Aldosterone antagonists - Spironolactone and Eplerenone (block aldosterone receptors to decrease conc. of Na+/K+ pumps = increase water in tubule)
eg. Sodium channel blockers - Amiloride, Triamterene
5% of filtered sodium excreted (weak)
Side effects: hyperkalaemia
Antidiuretics
Act on the collecting tubule
Released from the posterior pituitary gland to increase the number of aquaporin’s by V2 receptors to increase the passive reabsorption of water
eg. Vasopressin (ADH), Desmopressin
Vasopressin: very short duration of action, injection/infusion only, increases BP
Desmopressin: longer duration of action, nasal spray/tablets, no affect on BP
