Overview of high blood pressure medication
About this section
This section is useful for people who want to find out about any high blood pressure medication they have been prescribed. You can see why that particular drug may be the best for you or check if any symptoms you might be experiencing are likely to be side effects. It may also point you towards alternatives that you could discuss with your doctor if you feel you might benefit from a change.
The way the body controls blood pressure is quite complicated, however a little bit of easily understood science can help you to understand how drugs affect this system to lower blood pressure. click here, otherwise a more basic explanation follows.
This page has a brief description of each type of high blood pressure medication and there is also a link to more detailed information for anyone who wishes to know more.
How antihypertensive drugs work
Put simply, your blood pressure is determined by just two things: the output of your heart (how much blood is flowing), and the resistance from the blood vessels.
Any high blood pressure medication must therefore affect(directly or indirectly)one or both of those two elements - cardiac output (blood flow)and resistance.
Some drugs slow the heart or reduce how much it pumps with each beat (reducing cardiac output and blood pressure), some cause the kidneys to get rid of sodium which has the side effect of reducing the volume of water in the blood thus (indirectly) reducing cardiac output and therefore blood pressure). Other drugs relax blood vessels thus reducing resistance and bringing down blood pressure.
One more thing. The body's priority is to always keep blood pressure high enough to push blood to where its needed. The brain in particular must have a good flow at all times, - that's why if you stand up suddenly you may feel that your pulse speeds up - your body is reacting to increase blood pressure so that it can pump blood up to the higher level. Standing up too suddenly can make you feel light headed as the heart cannot react quickly enough. Some treatments that reduce blood pressure can affect the body's ability to react which is why some drugs make cause dizziness on standing - the heart is reacting too slowly. This is called postural hypotension
And that is all you really need to know!
I have listed the common types of high blood pressure medication below. You will notice that the list reads like a defensive line-up in a football team: blockers, inhibitors, antagonists etc! This is because many of these drugs block parts of the body's complex regulatory system. It is not surprising that there are sometimes side effects, although I prefer to think of the cup being half full - it is quite surprising that so many of them are so well tolerated!
NB: Most drug names given here are the generic names. Drugs produced commercially have a generic (chemical)name and a brand or trade name. So for example you have paracetamol (generic) then you have the trade name which will vary from company to company - e.g. Panadol, Tylenol. While a drug is still under patent, only one company makes it so it will have one trade name, though this may differ between countries.
Diuretics (water tablets)
Diuretics are often referred to as water tablets because they increase the output of water in the urine. Diuretics also increase the excretion of salt in the urine.
They are one of the most tried and tested types of high blood pressure medication available and are both cheap, effective and well tolerated. They are most often the first prescribed drugs and are good for treating elderly patients.
There are different classes of diuretic - the thiazides are the most commonly prescribed.
You would expect diuretics to work by reducing fluid, and while they do reduce plasma volume (plasma is the watery part of blood) their main effect is to reduce the resistance of blood vessels.
There are other types of diuretics which are less often prescribed, for more detail on diuretics click here.
Beta blockers block the effects of body chemicals that increase blood pressure by making the heart beat stronger and faster (adrenaline / epinephrine). The majority of beta blockers have a generic name that ends in 'OL', for example atenolol.
Beta blockers are good for patients who have had a heart attack or who have angina.
Generally speaking they should not be used in patients who have asthma, wheezy bronchitis or diabetes. This class of drugs has a variety of subtypes - some should not be used in patients with heart failure but others have a property that, conversely, makes them quite effective for the same condition.
You can read more detail about beta blockers by clicking here.
Calcium antagonists, (calcium channel blockers)
These drugs are very effective at making blood vessels relax. As you know well by now, this reduces resistance, and thus blood pressure. It also benefits the heart by relaxing the arteries that supply blood to the heart itself thus improving blood flow to the heart.
This class of high blood pressure medication works - at a cellular level - by affecting the mechanism that makes blood vessels contract. Because of this mode of action, some drugs in this class sometimes cause the heart to speed up (responding to try to restore blood pressure) which some people find uncomfortable. The newer calcium antagonists do not tend to have this effect though and these drugs are very well tolerated.
(By the way, do not take this to mean that if calcium blockers are good then eliminating calcium from the diet is good! That is not the case.)
For more detail on these drugs click here.
These are very effective drugs that interfere with yet another body mechanism that constricts blood vessels, (the A stands for Angiotensin which makes blood vessels constrict). They decrease resistance but their mode of action does not tend to cause the heart to speed up in response.
They also have a useful protective effect on the kidneys. This makes them a preferred drug for people showing the unwanted effects of blood pressure on the kidneys, something which is especially common in diabetics.
A common side effect of these drugs is an irritating dry cough - logically enough called ACE cough. These drugs are very effective and you can read more about them here.
Angiotensin II receptor blockers (ARBs)
These are sometines referred to as Angiotensin receptor antagonists - there is that name angiotensin again! You would be right to think that these work in a similar way to the ACE inhibitors. They also share some properties with them such as being 'kidney friendly'. They do not cause the ACE cough though.
ARBs are a relatively new high blood pressure medication and can therefore be more expensive than the older ones.
Click here for more information.
Renin inhibitors work in a similar way to the drugs blocking angiotensin but exert their effect further back down the line. Renin is the enzyme that produces angiotensin, so blocking it effectively blocks angiotensin's blood pressure raising effects.
This is the newest class of high blood pressure medication and the only commercially available renin inhibitor is Aliskiren (brand name Tekturna, from Novartis). Aliskiren is used either on its own or in combination with other drugs. It has so far proven to be effective and well tolerated and it is thought that it may have beneficial effects in protecting the kidneys especially in diabetic patients. Longer term information is not yet available.
For more detailed information click here.
Other types of high blood pressure medication
You can read about other types of less commonly used high blood pressure medication by clicking here. These include alpha blockers and some drugs that work directly via the brain or on other hormones that are part of the blood pressure regulatory system.
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|This page was last modified on : May 12, 2011. |