Thiazide Diuretics

Question 1

examples

Answer 1

bendroflumethiazide and metolazone

Question 2

mechanism of action

Answer 2

blocks the Na+/Cl- co-transporter in the distal convoluted tubule hence increasing water loss

Question 3

why are thiazide diuretics not that potent

Answer 3

because over 90% of sodium in the filtrate has already been re-absorbed by the time the filtrate reaches the distal convoluted tubule

Question 4

pros of thiazide diuretics

Answer 4

• they are well absorbed orally

- they cause vasodilation to reduce total peripheral resistance (mechanism of this is unknown)

Question 5

cons of thiazide diuretics

Answer 5

• ineffective if the Estimated glomerular filtration rate is less than 30ml/min/1.73 metres squared
• hypokalaemia, hyponatraemia, hypomagnasaemia
• metabolic alkalosis
• hypercalcaemia
• hyperglycaemia
• hyperlipidaemia
• hyperuricaemia thiazides classica precipitate gout

Question 6

why do thiazide diuretics cause hypercalcaemia

Answer 6

1. thiazide diuretics cause water depletion in the proximal convoluted tubule which causes compensatory increase in sodium re-absorpion in the proximal convoluted tubule which generates an electrical gradient leading to passive calcium re-absorption
2. Na+/Cl- transporter is blocked therefore, there is reduced sodium in the cell which causes the Na/Ca+ EXCHANGER ON THE BASOLATAERL MEMBRANE to become activated bringing sodium into the cell and moving calcium into the blood