Thiazide diuretics

Question 1

what are some examples of thiazide diuretics

Answer 1

• bendroflumethiazide, indapamide, chlortalidone

Question 2

What are the indications for use

Answer 2

• Alt 1st line Tx for HTN (where Ca channel blocker would otherwise be used - oedema, HF)
• Add on Tx for HTN (CaCB, ACEI or ARB)

Question 3

What is the mechanism of action

Answer 3

• Inhibit Na+/Cl- co-transporter in distal convoluted tubule of nephron
• prevents reabsorption Na + osmotically ass H2O
• diuresis = initial fall in extracellular fluid vol
• over time compensatory changes (e.g. activation RAAS) reverses in part
• Long-term antihypertensive effect mediated by vasodilation

Question 4

What are the side effects

Answer 4

• Hyponatraemia
• Urinary potassium loss –> hypokalaemia –> cardiac arrhythmia
• Impotence (men)

Question 5

What are the contraindications

Answer 5

• Hypokalaemia
• Hyponatraemia
• Gout (reduce uric acid secretion)

Question 6

What are the interactions

Answer 6

• NSAIDS (reduce effectiveness - low dose aspirin not a concern)
• Loop diuretics (also low serum K+)