ACE inhibitors are medicines that are used mainly in the treatment of hypertension (high blood pressure) and heart failure. They are also used in some people with diabetes, for some forms of kidney disease, and after a heart attack to help protect the heart. They have a variety of effects on the body. Their ability to relax blood vessels is one of the most important. The side-effects most commonly associated with ACE inhibitors are usually minor. A common side-effect is a persistent dry cough.
ACE inhibitors are a class (group) of medicines that are used in the treatment of various disorders. Their correct name is angiotensin-converting enzyme inhibitors - which is usually shortened to ACE inhibitors. They include: captopril, cilazapril, enalapril, fosinopril, imidapril, lisinopril, moexipril, perindopril, quinapril, ramipril and trandolapril. Each of these medicines also has various different brand names. Some ACE inhibitor medicines are also part of a combined tablet with a calcium-channel blocker medicine or diuretic medicine (water tablet).
ACE inhibitors are used to treat a number of different conditions:
For more information see separate leaflets called 'High Blood Pressure (Hypertension)', 'Heart Failure', 'Diabetes - Diabetic Kidney Disease', 'Myocardial Infarction (Heart Attack)', and 'Chronic Kidney Disease'.
ACE inhibitors prevent the body from creating a hormone known as angiotensin II. They do this by blocking (inhibiting) a chemical called angiotensin-converting enzyme. This has a variety of effects but essentially relaxes blood vessels and helps to reduce the amount of water re-absorbed by the kidneys. These actions help to decrease blood pressure as explained below.
Your body has a number of different ways of maintaining your blood pressure, but there are two main elements. One of the major factors is the resistance of the body's blood vessels. If the blood vessels constrict (tighten), resistance increases. If the blood vessels dilate (relax), the resistance is lower. If you have the same amount of fluid travelling in one vessel, the pressure will be higher when the vessel is constricted than when it is relaxed.
The other major factor influencing blood pressure is how much blood is pumped out of the heart. In a healthy person this depends on your heart rate (pulse) and the amount of blood that enters and leaves the heart's chambers. This is known as cardiac (heart) output.
Your blood pressure is the result of combining these two factors. It will be high if your vessels are constricted and there is lots of blood circulating through the heart. It will be lower if your vessels are dilated and there is less blood circulating through the heart. ACE inhibitors work by targeting both of these systems.
Blood is not just made up of red blood cells but also contains a large amount of fluid called plasma. Your kidneys control how much fluid you keep in your blood and how much you lose as urine. By re-absorbing (retaining) water that would otherwise become urine, the kidneys increase the amount of fluid in the blood. This increases blood volume.
In good health you have an intricate system set up to maintain your blood pressure. When your kidneys sense that your blood pressure has dropped a substance called renin is released into the bloodstream. Renin works on another chemical to form angiotensin I. Then the angiotensin-converting enzyme (ACE) changes angiotensin I to angiotensin II.
Angiotensin II is the active hormone. It has three main effects:
Increasing the volume of the blood by adding more water and constricting your blood vessels increases blood pressure.
ACE inhibitors stop angiotensin I from becoming angiotensin II. This reduces the amount of angiotensin II which causes blood vessels to dilate. The amount of water put back into the blood by the kidneys decreases. These actions reduce blood pressure.
There is another group of medicines called angiotensin-II receptor antagonists (for example, candesartan, losartan). These work in a similar way to ACE inhibitors. An angiotensin-II receptor antagonist may be used instead of an ACE inhibitor if you have problems or side-effects with taking an ACE inhibitor (such as a persistent cough).
Clinical trials suggest ACE inhibitors are all about equally effective at treating hypertension and heart failure.
You cannot buy ACE inhibitors. They are only available from your pharmacist, with a doctor's prescription. These medicines require special monitoring of your kidneys.
Your doctor will advise you how to take your medication, including how often. Generally, you will be started on a low dose to make sure you are coping well and that your blood pressure responds in an appropriate way.
In some people the first dose can cause a drop in blood pressure immediately. The following is advice for starting ACE inhibitors:
A blood test is usually done before starting an ACE inhibitor, and about 1-2 weeks after the first dose. You may also require further blood tests as your dose increases. These tests check on the function of the kidneys. The kidneys are affected in a small number of people who take an ACE inhibitor.
For people with hypertension, a blood test every year is then usual. If you have heart failure you will need more frequent blood tests - usually every 3-6 months.
A very small number of people may be required to start their treatment with ACE inhibitors in hospital so that careful monitoring can be undertaken.
These medicines can work very quickly in hypertension. If you have heart failure it may be weeks or months before you notice an improvement in your symptoms.
Once you have started taking an ACE inhibitor you will generally keep taking it indefinitely, unless you experience an adverse effect.
A full list of people who should not take ACE inhibitors is included with the leaflet that comes with your medicine. If you are prescribed ACE inhibitors, read this to be sure you are safe to take it. For example, people who should not take ACE inhibitors include:
A common side-effect associated with an ACE inhibitor is hypotension (low blood pressure). You may have no symptoms of this, or it may make you feel dizzy. If you experience this you should report it to your doctor. Around one in ten people who take an ACE inhibitor have a persistent dry cough. Less common side-effects include angio-oedema (swelling of the lips, eyes or tongue) and a decline in kidney function.
Note: the above is not the full list of side-effects for these medicines. Please see the leaflet that comes with your particular brand for a full list of possible side-effects and cautions.
A number of medicines may interact with ACE inhibitors. In particular, non-steroidal anti-inflammatory drugs (NSAIDs), diuretics (water tablets) and lithium. Your doctor will normally check what other medicines you take and give further advice about this.
So, make sure your doctor knows of any other medicines that you are taking, including ones that you have bought rather than been prescribed.
If you think you have had a side-effect to one of your medicines you can report this on the Yellow Card Scheme. You can do this online at the following web address: www.mhra.gov.uk/yellowcard.
The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that medicines may have caused. If you wish to report a side-effect, you will need to provide basic information about:
It is helpful if you have your medication - and/or the leaflet that came with it - with you while you fill out the report.