This information is for people who have high blood pressure. It tells you about a group of drugs called alpha-blockers, which are used to treat high blood pressure. It is based on the best and most up-to-date research.
Do they work?
Yes. If you have high blood pressure (hypertension), taking an alpha-blocker can lower your blood pressure and keep it down.
Alpha-blockers are as good at lowering blood pressure as other drugs available called beta-blockers, diuretics, ACE inhibitors, and calcium channel blockers.
But alpha-blockers aren't as good as some other treatments at protecting you against having a heart attack, having a stroke, or getting heart failure. They aren't usually used unless you're already taking other drugs, but your blood pressure is still high. 
What are they?
Alpha-blockers drugs that help lower blood pressure. Some common alpha-blockers (and their brand names) are:
Once you start taking medicine to control your blood pressure, you will probably need to stay on it. If you stop taking it, your blood pressure may go up again.
You may need to take more than one medicine to bring your blood pressure down. Most people need at least two drugs. 
How can they help?
Taking an alpha-blocker can lower your blood pressure and keep it down.
Alpha-blockers aren't as good at protecting you against heart failure as diuretics. 
How do they work?
The walls of your veins and arteries include a layer of muscle. Sometimes, this muscle can tighten up, making your blood vessels narrower. Blood can't flow through narrow vessels very easily, so it ends up pushing against the vessel walls more strongly. This means your blood pressure goes up.
The muscles that line your blood vessels have areas called alpha receptors. When these areas are activated, the muscles tighten. Alpha-blockers stop this happening by blocking the receptors. So, your blood vessels stay relaxed and open, making it easier for blood to flow through them. This lowers your blood pressure.
Can they be harmful?
Side effects of alpha-blockers are usually mild. But some people have a fainting spell with the first dose or two. So, doctors may start with a low dose and then gradually increase it over a few weeks.
Other common side effects include a headache and swelling of the ankles. You may also feel dizzy or tired.
How good is the research on alpha-blockers?
Research shows that alpha-blockers help to lower blood pressure just as well as other treatments.  Studies have included over 120,000 people, although people were often taking several drugs, not just alpha-blockers.
As well as lowering blood pressure, alpha-blockers cut the risk of dying from a stroke or a heart attack, but not as well as some other treatments.
One problem with alpha-blockers is that they aren't as good as diuretics for preventing heart failure. 
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