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Diuretics are the most commonly prescribed anti hypertensive agents.Thiazide diuretics which  was introduced many decades ago ,  lost popularity  in recent years ,  again got a second life after  the publication of ALLHAT trial recently. Now diuretics has become the  the drug of first choice in almost any hypertension unless any specific contraindication.

The most commonly used thaizide is hydrochlorthiazide ,and chlorthalidone.The blood pressure reducing effect is so consistent and smooth , all the currently popular molecules like ACE inhibitors and ARBs come with a combination with thiazide. While every one is clear diuretics are  effective anti hypertensive agent How it does is not clear.

How does a diuretic reduce blood pressure?

A. The exact mechanism is not clear. May not be uniformly effective in all patients  with HT.

B . Salt sensitive HT respond well to diuretics.

C. Volume correction /free water clearance might be a factor

D. Direct effect on vascular smoth muscle documented.The sodium transporter is blocked and  hence   calcium : sodium exchange is prevented .This depletes  intracellular calcium  in vascular smooth muscle cells .Less calcium for actin myosin interaction and hence vasodilatation

E. Thiazides combine well with all other antihypertensive drugs (ACEI, ARB, Beata blockers, calcium blockers)

F. Loop diuretics  like frusemide  can never be  a good antihypertensive agent.

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