Diuretics Drugs in treatment Hypertension
Thiazide diuretics: As HydroChloroThiaZide (HCTZ) PO 12.5 or25mg onced aily)
-Antihypertensive effects can be achieved in many patients with 12.5 mg daily of Chlorthalidone or Hydrochlorothiazide
-When used as monotherapy → the maximal daily dose → should not exceed 25 mg of Hydrochlorothiazide or Chlorthalidone.
- Mechanism of action of Thiazide diuretics:
–Thiazide diuretics→ initially ↓ BP by inhibit Na+/ Cl¯ & H2O re-absorption→ ↓ blood volume → ECF volume shrink ,so→ COP declines
–After 6–8 weeks → COP returns toward normal while PVR declines
– Thiazide diuretics → act primarily on the kidney but secondarily on Blood vessels
Therefore → the initial antihypertensive effect seem to be mediated by ↓intravascular volume → ↓COP → ↓BP → ↓ preload
-With chronic use → the plasma volume returns to nearly pre-treatment level after a few weeks due to development of tolerance after prolonged use
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MoA of Thiazide diuretics:
Therefore → the initial antihypertensive effect seem to be mediated by ↓intravascular volume → ↓COP → ↓BP → ↓ preload
then cause decrease of total vascular resistance.
-With chronic use → the plasma volume returns to nearly pre-treatment level after a few weeks due to development of tolerance after prolonged use
see this image>>
- Advantages of Thiazides:
The pharmacokinetic & pharmacodynamic characteristics of the Thiazides make them especially useful in the treatment of chronic HTN.
- Thiazide diuretics have longer duration of action than loop diuretic
- They are well tolerated even in elderly patients
- They ↓ the incidence of fracture in elderly patients
- Therapeutic uses of Thiazides:
– HTN: Hydrochlorothiazide → the 1st line therapy (DOC) → that can provide adequate treatment for primary mild to moderate HTN with otherwise normal heart & kidney function
–Thiazide diuretics preferred in:
- -Particularly effective in patients with volume-based HTN & African-American patients (black)
- –Elderly patients & ISH in elderly
