Treating Hypertension

In treating hypertension one of the first and most obvious questions is - 'are the targets we set for blood pressure lowering achievable?' Certainly working in a hospital setting many doctors would be forgiven for thinking that often they were not, given the number of patients that we see on various anti-hypertensive regimes who have blood pressures significantly above their targets.

Why should this be so?

There are probably multiple reasons but the two commonest are lack of compliance (that is the patients aren't actually taking the tablets) and undertreatment (that is the patient hasn't been prescribed enough of the right medications to achieve an adequate fall in their blood pressure).

Compliance is perhaps not an unexpectected issue given that most people who are diagnosed as having hypertension felt perfectly well before the doctor or nurse told them that they had high blood pressure and they are unlikely to receive the news that they should now be on tablets for life with much enthusiasm. Many people in these circumstances feel that they are being turned from a 'healthy individual' into a 'patient' and would rather maintain their former status off all medications! The key to the person with hypertension overcoming this barrier is to recognise that taking tablets to lower the blood pressure doesn't make them a patient but is to prevent them from becoming a patient in the future. The key to the doctor overcoming this barrier is to find medications that don't give the patient side effects and that actually reduce the blood pressure to target thereby encouraging the person to keep taking them!

It has been shown in most of the clinical trials that the majority of patients need combination therapy to adequately lower their blood pressure with many people on three or four different classes of tablets. In the UK it has been shown that 66% of patients are only prescribed a single drug and less than 10% are are on three drugs. Less than 50% of the patients in the UK being treated for hypertension reach their target blood pressure.

The reason that this is important is because higher levels of both systolic and diastolic blood pressure are associated with Stroke, Coronary Artery Disease, Heart Failure, Dementia, Peripheral Vascular Disease and Reduced Kidney Function. Furthermore, lowering blood pressure reduces these illnesses and their associated mortalities. For instance, lowering the systolic blood pressure by 12mmHg and the diastolic BP by 6mmHg reduces Stroke risk by 40% and Coronary Heart Disease risk by 20%. It is also worth noting that 50% of stroke patients were known to have hypertension prior to their stroke.

Which drugs?

Which drugs should be used for treating hypertension? The simple answer is anything that achieves the desired reduction in blood pressure. However, we have a lot of evidence from a very large number of clinical trials for effectiveness of certain mainline drugs and these include:

• Beta-blockers
• Diuretics
• Angiotensin converting enzyme inhibitors (ACE inhibitors)
• Angiotension II receptor blockers (ARB's)
• Calcium channel blockers

So which of these drugs should be tried first? ....... and, as more than one drug is likely to be needed, what are the best combinations?

To an extent this depends on whether the person has any other medical conditions, as some of the medications in the list above may be helpful for other conditions as well as hypertension, and others may worsen pre-existing medical problems and, therefore, in this group of patients careful thought should be applied to which tablets to try first, and in which combinations. The tables below gives examples of where anti-hypertensive medications may be helpful or contra-indicated with in people with pre-existing other medical conditions.

In patients with no other problems the choice of first-line medication largely comes down to age and race. Younger people tend to respond better the ACE inhibitors, ARB's and Beta-blockers and people of black African decent and people over 55 years of age to calcium channel blockers and diuretics. This is because in the first group the hypertension appears to be more often associated with high levels of renin (a chemical produced by the kidneys) whereas in the other groups it isn't.

Within the last few years there was a widespread proprosal that in people with hypertension but no other significant illnesses that might affect the choice of medication, that an ABCD approach should be used. Here the A stands for ACE's and ARB's, the B for Beta-blockers, the C for Calcium channel blockers and the D for Diuretics.

It is suggested that if the most appropriate first drug is from group A or B, then if a second drug is needed then one from class C or D should be used. Conversely, if the first drug is from C or D then the second should be from A or B. If a third drug is required then one from either of the remaining classes can be chosen and if a fourth drug is required then this would come from the remaining class.

Therefore if we were treating a 64 year old white man with no other illnesses then a logical starting point would be a Calcium channel blocker (C). If he required another medication then the addition of either a drug from A or B would be appropriate and in this case I would probably choose an ACE inhibitor (A). If further medication was required either a Beta -blocker or a Diuretic (D) would be appropriate but I would usually choose a diuretic for two reasons. First diuretics and ACE inhibitors are both effective in their own right but diuretics further enhance the anti-hypertensive effects of the ACE inhibitor giving added blood pressure lowering. Second, whilst Beta-blockers are very good drugs in any number of cardiovascular conditions (hypertension, angina, protection post heart attack, rhythm disturbances etc) certain Beta-blockers have been shown to slightly increase the chances of later developing diabetes and therefore if other medications are equally effective in adequately lowering blood pressure then it would seem more reasonable to use them first.

Whilst these four classes of drugs are the mainstay of blood pressure treatments there are several other drugs that are effective and are widely and appropriately used particularly where any of the above drugs are contra-indicated, not tolerated or appear ineffective. Alpha-blockers and centrally acting drugs (those that work at the level of the brain) are often used.

Since so many people need several different types of anti-hypertensives to achieve their target blood pressures there is growing interest in producing combination medications combining different drugs and it likely that these will become more widely used in the future.

Achieving your target blood pressure

As can be seen from all of the above there are many different medications that can be used to treat blood pressure and most people can get their blood pressure down to the target. It may, however, take some time and patience to find the right medications in the right combination to achieve that control. It should also be noted that the blood pressure may take several weeks to fully respond to new medications. For all of these reasons both the doctor and the patient should be prepared to take time over establishing the right medication regime to achieve blood pressure control. It is also important that you know what your target is, and that you are told what your blood pressure is when it is measured in the surgery or clinic. This is the only way that you will know whether you are being adequately treated. I am amazed at the very large number of patients who have been on anti-hypertensive medications for years and have no idea what their blood is, or should be, and when asked usually reply 'he said it was up a bit' or 'she said it was OK' !

Clearly there are some patients in whom target blood pressures cannot be acieved (usually because of drug intolerances) but even here every reduction than can be achieved is still of significant health benefit in reducing cardiovascular risk and in particular stroke. It has been shown that if we were able to get the whole population down to their target blood pressures we would prevent 75% of all the strokes - an illness well worth avoiding.

Drugs used to treat hypertension

The table below list some of the drugs more commonly used in the treatment of hypertension. This is not meant to be a comprehensive or complete list but shows many of the commoner medications and the class of medication to which they belong.