Thiazide-Like Diuretics For High Blood Pressure


Thiazide diuretics (eg bendroflumethiazide, chlortalidone, cyclopenthiazide, indapamide, xipimide, metolazone) may be used as a first line treatment or combined with other antihypertensive drugs to boost their action.

They mainly work via the kidneys by increasing the loss of fluid and salts from the body, and are popularly known as diuretics. As well as reducing the volume of fluid in the circulation, thiazide-like diuretics also cause a generally mild dilation of small arteries (arterioles) to lower arteriolar resistance.

When you first start taking the tablets, you will pass water more frequently than usual for the first few days, then this effect tends to disappear within a couple of weeks as dilation of the arterioles occurs.

The initial diuretic effect usually comes on quickly, within a few hours, so you will usually be advised to take the first thing in the morning to reduce trips to the bathroom at night.

Relatively low doses of thiazide-like diuretics are needed and, on average, they reduce your systolic blood pressure (your upper reading) by 7.3mmHg when used alone. Higher doses tend to have no further effect and are more likely to cause side effects such as salt imbalances which can cause muscle cramps and dizziness.

Many popular dual therapies combine a thiazide-like diuretic with an ACE inhibitor, a calcium channel blocker or an angiotensin receptor blocker.

If your blood pressure is raised, self-monitoring is key to maintaining good control. 

Click here for advice on choosing a blood pressure monitor to use at home.

See my recommended upper arm blood pressure monitors.

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