High blood pressure

Side effects of treatments

Some of the people interviewed talked about certain medications that were particularly likely to produce side effects (such as impotence) that they were not prepared to accept.

Possible side effects from taking beta-blockers include severe tiredness and wheezing and consequently they are not recommended for people known to have asthma. However occasionally this symptom can arise in people who have not previously been thought to suffer from asthma. One patient mentioned nightmares but it is not clear whether these would have happened without the drug.

People's experiences of using ACE inhibitors varied. Some were reasonably happy on an ACE inhibitor after other medications had been unsatisfactory. One person was particularly pleased to have found lisinopril, after unpleasant side effects on a betablocker. The most dramatic story was from one person who, as a young woman, was treated in intensive care after a crisis and found that only the newly available Capozide brought down her blood pressure from dangerously high levels.

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Problems included feeling lethargic or slowed down, a reduced sex drive, having a tickly throat or cough or feeling that coughs were harder to shake off, a runny nose and dizzy or fainting spells.

Tiredness was a particular problem to those with physically or otherwise demanding jobs.

As for other drugs, many people taking a calcium channel blocker were fairly satisfied, but several described dizziness. Two women experienced problems in their legs' one had severe pain and another had ankle swelling.

For diuretics, the main problems related to the frequent need to pass water during the hours following taking the medication. The only other side effects attributed to these were dry skin and hair loss.

Not many people were given alpha blockers but one described experiencing severe dizziness while another had disturbing mental changes.


Some people on combinations of drugs were not sure whether their side effects were caused by one of them, or by the interactions of the various tablets.

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Impotence is described as a possible side effect from several different drugs, in particular diuretics and alpha-blockers.

Some doctors worry about warning their patients of the possible side effects from drugs, believing that if they do they are more or less ensuring that the patient will experience them. However, several published studies have shown that this is very unlikely to happen. One man who had experienced impotence was dismayed to discover that this had probably been caused by prolonged use of bendrofluazide (a diuretic) and that he had never been warned that this was a likely problem.

Overall it was clear that if there are adverse side effects to treatment it is important to report back to the doctor as soon as possible to perhaps change the drug regimen. On the other hand, it was also clear many patients suffered no side effects or if they had, a combination of drugs was found to avoid these (see 'Selecting treatment').

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The following list covers most of the classes of drug used to lower blood pressure, together with their most common or serious possible side effects'

Thiazide diuretics - low-dose "water tablets"

Bendroflumethiazide is the most widely used in the UK. Others include chlortalidone, cyclopenthiazide, indapamide and xipamide. The commonest side effects are passing urine more frequently and sexual difficulties in men. They can also cause indigestion, faintness on getting up, and generalised weakness due to lack of potassium or sodium. Gout can occur due a build up of uric acid, and the blood sugar may be raised, though it falls again on stopping the drug. Despite these potential adverse effects, this group of drugs has the greatest known benefits of any blood pressure lowering class.


These are drugs with names ending  in -olol. The most widely used in the UK for blood pressure lowering are atenolol and bisoprolol; there are 12 others licensed in this country. They block some of the actions of adrenaline and slow the heart as well as lowering blood pressure. They should not be used in people with asthma and should be stopped if they cause wheezing or shortness of breath. Common side effects include cold hands and feet, tiredness and sometimes sexual difficulties in men.


The most commonly used blood pressure lowering drugs in this group are doxazosin and prazosin; others are indoramin and terazosin. They can cause dizziness on getting up, mood disturbances and tiredness; on the other hand, they can reduce the symptoms of prostate enlargement in men.

ACE inhibitors

These are drugs with names ending in -pril. The two most commonly used to reduce blood pressure are ramipril and lisinopril; there are nine others licensed in the UK. They work by blocking the conversion of one chemical (angiotensin) into its more active form, but they also stop the breakdown of the chemicals which cause coughing. Most people taking ACE inhibitors therefore tend to cough for longer when they get a cold, and a small percentage find that they have a dry tickly cough all the time. A very small number also get swelling of the lips or face. Otherwise, the commonest reason for stopping ACE inhibitors is feeling faint on getting up, but this is uncommon after the first dose.

ARBs - angiotensin receptor blockers, also known as A2RAs

These are drugs ending in -sartan. Losartan and candesartan are widely prescribed, and there are also irbesartan, eprosartan, olmesartan, telmisartan and valsartan in the UK. These work one step further along the chemical pathway from the ACE inhibitors in the previous section, with the advantage that they do not cause cough. They have the fewest side effects of any blood pressure lowering group.

Calcium channel blockers - also known as calcium antagonists

Most of these drugs have names ending in -dipine, and the most commonly used for blood pressure lowering are amlodipine and felodipine. There are nine others in the UK, including the older drugs verapamil and diltiazem, which have more adverse effects and are usually only used in particular situations. Calcium channel blockers do not affect calcium in the bones, but work by opening up small blood vessels. Thus they all tend to cause flushing and warm peripheries and the commonest reason for stopping these drugs is headache.

Other drug classes

In certain situations additional blood pressure lowering needs to be achieved with drugs that work in different ways from those listed above. These include spironolactone, hydralazine, minoxidil, clonidine and methyldopa. Each has its own range of possible adverse effects.

For more information on high blood pressure see our Resources and Information section.

Last reviewed December 2011.

Last updated January 2012.


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