ACE inhibitors block the action of an enzyme (angiotensin converting enzyme, or ACE) to prevent the formation of a substance called angiotensin II which causes arteries to constrict. By blocking its formation, your small arteries and veins can dilate so your blood pressure falls.
Dilation of blood vessels supplying the kidneys also increases the amount of fluid and sodium lost as urine for a further beneficial effect on blood pressure.
On average, an ACE inhibitor reduces systolic blood pressure (your upper reading) by 6.8 mmHg when used alone.
Kidney function and salt balance should be checked before treatment is started. Low doses are used initially as ACE inhibitors can cause a sudden fall in BP. Their most troublesome side effect is a dry cough.
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.
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