Thiazide Diuretics

Question 1

Give some examples of thiazide diuretics

Answer 1

Bendroflumethiazide

Question 2

Give some examples of thiazide like diuretics

Answer 2

Indapamide, chlortalidone

Question 3

How do thiazide diuretics work?

Answer 3

Work on the DCT
Block the sodium chloride channel in the DCT
Na is therefore not reabsorbed along with water
This has a moderate diuretic effect - compensatory RAS system can overcome effects
Vasodilation also occurs which accounts for the long term anti-hypertensive effect

Question 4

What are the common uses of thiazide diuretics?

Answer 4

1. Hypertension
   - alternative first line for those over 55 or afro-carribean
2. Resistant hypertension
   - as an add on

Question 5

When are thiazide diuretics chosen over CCBs in hypertension?

Answer 5

If CCBs are unsuitable due to oedema or there are features of HF where thiazide diuretics would help

Question 6

What are the contraindications of using thiazide diuretics?

Answer 6

Hypokalaemia

Hyponatreamia

Question 7

When should you use thiazide diuretics with caution?

Answer 7

Those with gout as long term use can exacerbate attacks

Question 8

What are the common interactions with thiazide diuretics?

Answer 8

NSAIDs can reduce effectvieness
Any drugs excreted by kidney:
- Lithium: increased Levels
- Digoxin: hypokalamia can cause digoxin toxicity
Other drugs that lower potassium levels e.g. loop diuretics = cardiac arrhythmia’s

Question 9

What are the common side effects of loop diuretics?

Answer 9

Hypokalaemia --> arrthymias 
Hyponatraemia 
Increase in plasma glucose --> T2DM
Increase in LDL and triglyceride levels 
Impotence in men

Question 10

Does in increase dose of thiazide diuretics have much of a difference?

Answer 10

No - There is little to be gained from higher dose treatment, as this tends just to increase side effects without significantly improving the antihypertensive effect.

Question 11

What advice should you give to patients?

Answer 11

• Avoid NSAIDs

- Take tablet in the morning

Question 12

Summarise the effects of ACEi, ARBs, LOOP Ds and Thiazide Ds on potassium levels

Answer 12

ACEi and ARBS = HYPERkalameia

LOOP D and Thiazide = HYPOkalamia

Question 13

Why are ACEi/ARBS and thiazides good for clinical use?

Answer 13

Thiazides cause hypokalaemia, while ACE inhibitors and ARBs cause hyperkalaemia.
Thiazides activate the renin–angiotensin system, while ACE inhibitors/ARBs block it.
Therefore a combination of a thiazide and an ACE inhibitor/ARB is useful to improve blood pressure control and to maintain neutral potassium balance.