Hypertension

Summary

• Your blood pressure is the pressure within your blood vessels, and this pressure is generated by the pumping action of the heart, which is opposed by the resistance of the small arteries.
• A blood pressure measurement is made up of two parts: systolic and diastolic. This is why a blood pressure measurement is expressed as one figure "over" another, for example 120/80 mm Hg.
• Without blood pressure you’d die, but if it is too high it can kill you.
• Hypertension is especially dangerous because it frequently has no symptoms.
• Some factors and associated diseases increase your chances of developing hypertension which can eventually damage your heart, blood vessels, kidneys, eyes, brain and other organs.
• You CAN reduce your risk of the above with lifestyle modification.
• Once diagnosed with hypertension, you should take your prescribed drugs diligently and should not alter the dosages or stop taking your medication. Let your doctor prescribe another antihypertensive drug if you suffer from unwanted side-effects.
• New drugs and drug combinations are being developed on a continuous basis.
• You can lead a happy and long life if your hypertension is well controlled. 
   

Definition

Your blood pressure is the pressure within your blood vessels. This pressure is generated by the pumping action of the heart and counteracted by the resistance of the small arteries. 

Blood pressure is essential to life. It keeps the blood flowing through your body and provides oxygen and energy to your organs.

Your blood pressure is strictly regulated, as too low pressure causes dizziness, fainting and a lack of oxygen to your organs.  In fact, when a doctor uses the term “shock”, it usually implies that there has been a drastic drop in blood pressure, leading  to inadequate perfusion and oxygenation of vital organs like the brain and kidneys. Starved from their life-giving source of oxygen, these organs cannot function anymore, and the individual is at risk of dying unless corrective treatment is taken.
Too high blood pressure (either systolic or diastolic or both – see below) may damage blood vessels and vital organs over time. According to the World Health Organisation, hypertension is the leading global risk for death, responsible for 12,8% (7,5 million) of deaths worldwide. It is without any doubt one of the leading causes of heart attack, stroke, kidney failure, dementia, eye disease, and premature death. Together with cigarette smoking, high cholesterol, obesity and diabetes mellitus, it constitutes the so-called cardiovascular risk profile.

How does it work?

Your heart functions as a muscular pump which contracts rhythmically and pumps blood into your arteries. From your heart, through your large vessels (such as the aorta) your blood is channelled to your entire body through a circulatory system of smaller vessels. The resistance offered by these smaller arteries to prevent arteries from bursting, due to the dramatic pumping action, is very significant. Constriction of the muscle in the artery wall causes it to narrow, which increases the resistance and hence the pressure within. This can be compared to taking a garden hose and reducing the size of the nozzle. Pressure in a hose can of course also be raised by increasing the amount of water flowing from the tap. Similarly, the amount of circulating blood, and the strength of the heart muscle contractions, can also influence your blood pressure.

Your blood pressure increases and decreases according to the demands made on it. This enables you to play a vigorous game of tennis and also to get a good night’s sleep.

Blood pressure rises when you are active and falls when you are inactive. During restful sleep, your inactivity reduces the demand for oxygen and therefore blood pressure is usually lowest at night and highest when you get up in the morning.

There is also considerable variability in blood pressure. It may be transiently elevated under certain circumstances, and should not be confused with hypertension, which is a sustained elevation in blood pressure. For instance, when startled or threatened,  one’s blood pressure is raised through the effects of the “fight or flight” response, when your adrenalin levels are high. Experiencing pain can also raise pressure dramatically. Alcohol, nicotine and caffeine intake can cause transient elevations of blood pressure.

Blood pressure fluctuations are not problematic, as long as blood pressure rapidly returns to a normal baseline. It is the sustained increase in blood pressure that causes havoc, especially when accompanied by risk factors like smoking, high cholesterol and obesity and co-existing disease like diabetes. Some people have high blood pressure only in a medical establishment. This is termed  white coat or office hypertension and can be confirmed by showing that blood pressure is normal in a home setting. It is important to diagnose “white coating”, as treatment with antihypertensive drugs is unnecessary and can cause side effects.

Explaining blood pressure terminology

Hypertension is a condition where the pressure within your arteries is consistently too high.

If your blood pressure is too high, your heart must work much harder (and enlarges) to maintain adequate blood flow to your body. The long term effects of this pressure may cause the heart to fail and this is termed hypertensive heart disease.
A blood pressure measurement is made up of two parts: systolic and diastolic.

Systolic pressure occurs in arteries during heart contraction (which is called a systole) and diastolic pressure during the period of relaxation between beats. This is why a blood pressure measurement is expressed as one figure "over" another, for example 120/80  mm Hg Systolic pressure is obviously always higher than diastolic blood pressure. 

The measurement unit, millimetre mercury (symbol Hg), is derived from the distance that a column of mercury in the measurement instrument is pressed upward. If your blood pressure is recorded as 120/80, the number on top is the systolic pressure, and the bottom number the diastolic. 120/80mm Hg also happens to be the optimal blood pressure, although many people especially young women may have blood pressures as low as 90/60 mm Hg, and this is quite normal.

Pulse pressure is the difference between the two readings. In elderly persons the pulse pressure may rise because the diastolic pressure falls as a result of the large vessels becoming stiff . This is called isolated systolic hypertension and carries an even higher risk of complications. Although the diastolic may be “normal” or even low, it is essential that this type of hypertension be treated.

When is blood pressure considered high?

Researchers are of the opinion that the average  blood pressure during the day should not exceed 130/80 mm Hg. Hypertension is diagnosed when the blood pressure is consistently above  140 systolic or 90 diastolic. Between 130/80 and 140/90 it is called high normal blood pressure, and it is usual to progress to hypertension over the next 2 – 5 years unless lifestyle changes are made. In high risk patients like diabetics, blood pressure may be treated with drugs, even in the high normal range. The target blood pressure is less than 140/90, but in high risk patients (patients with more than two major risk factors, target organ damage or diabetes), this is lower at 130/80.

The following table shows the normal ranges of blood pressure and the stages of hypertension for South Africans. High normal blood pressure requires more regular monitoring. Stage 1 is less severe than Stage 3.

Blood pressure above 180/110 mm Hg is dangerous, and urgent medical attention needs to be sought. If the blood pressure is greater than 200/120 it can be rapidly life threatening and cause malignant hypertension.

Hypertension represents an arbitrarily determined level of blood pressure, above which the advantages of treatment are greater than the disadvantages.

Hypertension is diagnosed when blood pressure measurements are above either of these normal levels on two or more separate occasions. In patients who are at high cardiac risk, e.g. diabetics or patients with known heart disease, treatment for blood pressure may be indicated in the high normal range.

Elevated blood pressure readings may not always indicate that a person has hypertension, as in the case of white coat hypertension – high readings caused by a natural alerting response during blood pressure measurement (the emotional stress of having a doctor take your blood pressure). At home the blood pressure readings are completely normal and this condition generally carries no risk but needs to be monitored regularly, as some people with white coat hypertension may develop true hypertension in time.

Prevalence

Several community studies done by the Medical Research Council (MRC) showed that one out of every four people between the ages of 15 and 64 suffer from high blood pressure. Unhealthy lifestyle habits and eating habits play a great role in the developing of high blood pressure according to Dr Krisela Steyn, MRC researcher and project leader of several studies about blood pressure. However genetic predisposition also plays a major role and if there is a history of hypertension or stroke in your family, early screening is advised.

More than 6,2 million South Africans have blood pressure higher than 140/90 mm Hg. More than 3,2 million of these have blood pressure higher than 160/95 mm Hg, a level, which is unacceptably high, according to researchers. An estimated 53 men and 78 women die in South Africa each day from the impact of hypertension.

Black South Africans suffering from hypertension are at higher risk of developing cerebral bleeding, malignant hypertension, and/or kidney disease, leading to congestive heart failure. According to studies by Wits University, hypertension is responsible for 33% of heart failure cases in the black population. Indian and white South Africans with hypertension are at higher risk of developing coronary artery disease, leading to heart attacks. 

High blood pressure is only under control if it is stabilised below  a level of 140/90 mm Hg by means of treatment. Levels of 160/90 mm Hg do not translate to good control of blood pressure levels, since  any blood pressure higher than 140/90 mm Hg could lead to gradual organ damage.

Levels of blood pressure control are shockingly low, even in developed countries. In South Africa, only 21% of men and 36% of women with hypertension are taking drugs to reduce their blood pressure, while only 10% of men and 18% of women have their blood pressure levels reduced to the level that will eliminate the risk to their hearts, brain and kidneys. A study by Wits University showed that about 40% of the black population suffers from hypertension, but only 20% are on treatment. However, more than 30% of the 20% on treatment are nor treated to target, and their blood pressure levels are still to high to prevent target organ damage.

Patients who cease taking their medication because of unpleasant side effects must be made aware of the consequences of uncontrolled blood pressure. The good news is that due to a wide variety of different blood pressure treatments, a patient can be treated correctly without unwanted side effects.

Causes and types of hypertension

Most hypertension has no known cause. This is known as primary or essential hypertension.

About 5% of hypertension can be traced to underlying diseases, such as kidney disorders or conditions that cause narrowing of the arteries of the kidney.

 Hypertension are classified based on causes and characteristics.

There are two major types of hypertension and 5 subtypes.

The two major types are:

• Primary or essential hypertensionhas no known cause and is diagnosed in about 95% of  people. It has a strong genetic predisposition and is associated with poor lifestyle.
• Secondary hypertensionis often caused by specific diseases or factors (e.g. kidney damage) and is sometimes curable.

The other types include:

• Malignant hypertension. Unless properly treated it is fatal within five years for the majority of patients. This occurs particularly in young black men.
• Isolated systolic hypertension. This may occur in older people, and results from the age-related stiffening of the arteries. Treatment is of the utmost importance.
• White coat hypertension. It means blood pressure is only high when tested by a health professional. Persistent hypertension may develop in time.
• Resistant Hypertension. If blood pressure cannot be reduced to below 140/90 mmHg despite a triple-drug regime, resistant hypertension is considered.
• Masked hypertension. This is the opposite of white coat hypertension and is present in 10% of hypertensives. Masked hypertension will damage the heart and blood vessels in exactly the same way as in untreated patients.

Symptoms

Under the heading "Common Hypertension Symptoms" an author of a medical text left the entire page blank – he was emphasising the absence of symptoms seen in most people with hypertension. This highlights the fact that Essential hypertension,  which account for 95% of all cases of hypertension, rarely has any symptoms.

Most people with hypertension feel fine (are asymptomatic) and only learn of their hypertension during a routine examination or an examination for some other problem, or unexpectedly have a stroke or heart attack. You could be one of these people. This happens because hypertension may go undetected for years, causing silent damage to your heart, brain, blood vessels and kidneys and quite unexpectedly a person may suffer a heart attack or stroke or be told they have kidney failure. This is why all adults, even those who feel “healthy” and have a healthy lifestyle should be screened for high blood pressure on a regular basis.

Sometimes people who have been diagnosed with hypertension report headaches, dizziness, fatigue, and pounding of the heart. These symptoms may be related to hypertension.

More advanced cases of hypertension - especially with levels greater than 180/110mmHg -  may present the following symptoms:

• Headaches, especially pulsating headaches behind the eyes
• Visual disturbances
• Nausea and vomiting
• Disturbed levels of consciousness, such as sleepiness and even seizures in severe cases

In all these cases patients should seek urgent medical attention, as hypertension may be rapidly fatal. This is called malignant hypertension and is common in young black men.

Once complications have set in, symptoms may be related to this, e.g. shortness of breath and chest pain due to heart disease.

Who is at risk?

 In 90 to 95% of cases there is no known cause of hypertension. However, there are factors that contribute to the problem, called risk factors. If you have two or more of these risk factors, your risk for hypertension can be classified as “high”.

 Risk factors can be divided into three main categories:
1. Those you cannot control. These include your parents (determining your ethnicity,  your genes and thus your family history) and your age.
2. Risk factors you can control. These include overweight, lack of exercise , smoking, wrong food choices, use of  the contraceptive pill and several  recreational drugs.
3. Associated diseases or organ damage that can also increase your total risk. These include  high blood cholesterol levels, existing heart disease, angina, heart failure, diabetes, previous stroke (including so-called mini-strokes), kidney damage, damage to the retina of the eye, damage to the blood vessels.

Risk factors and associated conditions create a double-edged sword. Some risk factors will not only increases your chances of developing high blood pressure, but as soon as your are indeed hypertensive, some associated factors will increase your risk of developing complications such as cardiovascular disease and kidney failure. This, in turn, can increase blood pressure and a vicious cycle is the end result.

In summary, the following people display a major risk of developing hypertension, followed by complications and organ damage due to high blood pressure:

• Smokers (controllable factor)
• Those with high blood cholesterol levels (controllable factor)
• Those with a family history, i.e. brother/sister, father/mother with high blood pressure, diabetes, heart problems or a stroke (uncontrollable factor)
• Those with diabetes (uncontrollable factor)
• People older than 50 years (uncontrollable factor)
• African ethnicity (uncontrollable factor)
• Those who are overweight, especially  around the abdomen (controllable factor)
• Those with a family history of early coronary artery disease in a parent or sibling. i.e. before age 45 for men or 55 for women (uncontrollable factor)
• Those with bad eating habits, particularly sensitivity to sodium (salt) intake and low intake of potassium, magnesium and calcium
• Those with a high intake of alcohol, i.e. more than two drinks daily (controllable factors)
• Those with an inactive lifestyle (controllable factor)
• The use of the Pill, steroids such as cortisone and anti-inflammatory drugs can all contribute to higher blood pressure. (controllable factor)
• Abusers of drugs like “tik”, cocaine and other amphetamine-like drugs. Hypertension can be very dangerous in these circumstances.

Your doctor will take all your risk factors into account in an individualised management plan. It will influence decisions of when to start drug treatment, as well as the choice of medication. Special examinations and regular follow-up treatment will be needed to optimise your health.
 

Special note: Since hypertension often has no symptoms and may go undetected for years (it is often referred to as the silent killer), all adults, even if feeling healthy, should be screened for high blood pressure on an annual basis. Contrary to popular opinion, high blood pressure often occurs in younger people. Health care professionals should also routinely measure blood pressure in this group, especially if overweight or obese and there is a family history of hypertension.

Likely course of untreated hypertension

If you have hypertension, your heart works harder than it should to pump blood to distant tissues and organs. If this pressure isn't controlled, your heart enlarges and your arteries become scarred, hardened and less flexible. Eventually your overworked heart may not be able to pump and transport blood properly through stiff arteries.

These changes increase the risk of:

• Heart disease such as heart attacks (myocardial infarction, or the death of heart muscle)
• Heart failure (failure to pump enough blood to your body’s tissues and organs to meet their needs)
• Stroke
• Kidney failure. Kidney disease is silent and you must insist that your doctor check your kidneys with blood and urine tests.
• Peripheral vascular disease (any abnormal condition arising in the blood vessels outside the heart) especially to the legs. Peripheral vascular disease may cause cramps in the legs on walking and may even lead to amputation because of lack of blood.
• Dementia. The connection between hypertension and dementia is increasingly recognised and treatment can delay or prevent dementia.

The risk of complications increases along with an increase in blood pressure, but  there is not an abrupt cut-off point above which complications appear. Treatment and follow-up recommendations will depend on factors such as the severity of the hypertension and whether other organs, such as the kidneys, have been affected by it. Organ damage can occur if systolic, diastolic or both pressures are high.

Hypertension can damage the blood vessels that supply blood to the light-sensitive lining of the back of the eye (the retina). This damage, retinopathy, can lead to vision loss or blindness if untreated.

BUT: Hypertension doesn't have to be deadly. It's easy to diagnose and once you know you have it, it can be controlled. Many experts believe that improved detection, treatment and control of hypertension is a major reason why there has been a 50% decrease in death due to heart disease and a 57% decrease in death caused by stroke in America in the last 20 years.

Diagnosis

Hypertension is diagnosed only after several careful measurements show that the systolic and/or diastolic blood pressure is consistently above normal. This is because normal blood pressure fluctuates and stressful situations, such as a visit to your doctor’s rooms, can elevate your blood pressure temporarily. Note that in most cases a single reading is not sufficient and the effect of white-coat hypertension may be underestimated. In most cases an extensive work-up is not needed to diagnose hypertension.

How blood pressure is measured
Blood pressure is measured using a sphygmomanometer.  It consists of a soft cuff, wrapped around your upper arm, then inflated to put pressure on the arm and on the brachial artery that runs the length of the limb. This is linked to a column of mercury with precisely calibrated numbers A stethoscope is placed on the inner side of the elbow crease, just below the cuff. This is right above the main artery (the brachial artery) in your arm. Until a couple of years ago the manual method was the norm: listening to the heartbeat over the brachial artery on the inside of the upper arm while deflating the cuff and watching the mercury column fall. When the heartbeat became audible, it meant the pressure is just not high enough to cut off the blood flow in your brachial artery. The point at which this happens is measured and is counted as your systolic pressure. Releasing the pressure even more causes disappearance of the heart beat, and this is the diastolic pressure.

But in recent years new, automated blood pressure monitors that can accurately measure your blood pressure through electronic signals have become the  new  gold standard. Several readings from an automated blood pressure monitor from a reputable manufacturer are more reliable than any manual reading. Automated blood pressure monitors for use by the health care professional and at home are available. Devices that measure blood pressure at the wrist are not recommended.

Whether blood pressure is measured manually or with an automated machine, blood pressure should always be measured in the upper arm in quiet surroundings. The cuff needs to be the correct size and the subject needs to sitting with the back supported, the legs uncrossed and on the floor and the arm supported at heart level. Several readings need to be taken every 1-2 minutes until readings stabilise. Initial readings are often higher than later readings and the mean of the final 2 readings should be recorded. 

Have a health care provider check your blood pressure annually. He or she will measure the pressure of the blood in your arteries and detect subtle sounds when your heart contracts and between beats. The following tests are performed to diagnose hypertension and related conditions:

1. Routine investigations

• Physical examination and medical history confirm the presence of hypertension and determine its severity, evaluate possible damage to organs, establish the presence of associated diseases that increase the risk of complications and look for possible causes of secondary hypertension. The doctor will look into your eyes with a special instrument to assess possible damage to the retina.
• Creatinine  and potassium test– A blood test that indicates how well the kidneys are functioning and whether they are damaged.
• Urine analysis– Abnormalities, such as the presence of blood and protein, give an indication of kidney damage and may suggest that the kidneys are also involved in causing secondary hypertension.
• Blood glucose (fasting)– Can indicate the presence of diabetes, which increases the risk of complications.
• Fasting lipogram– Diagnoses high cholesterol, which adds to the risk of complications in the hypertensive patient.
• Electrocardiogram (ECG)– A recording of the electrical activity of the heart, which indicates the degree of damage to the heart and detects previous heart attacks.

If there is reason to suspect that blood pressure measurements taken in the doctor's rooms do not represent true blood pressure (for example, as a result of white coat hypertension), or if there are large fluctuations in blood pressure, out-of-office blood pressure monitoring over 24 hours may be needed. This can take the form of self-monitoring at home or continuous ambulatory blood pressure monitoring.

The 24 hour monitor is now considered a highly accurate and reproducible investigation and predicts outcome far more accurately than office blood pressure. It is not routinely advised but used for special situations. It must be remembered that a daytime mean blood equivalent to office 140/90 is 128/83.

2. Special tests to detect organ damage

Other tests may be done to determine if hypertension has caused damage to the heart or kidneys, or if the person has had a stroke:

• Chest X-ray– Shows the size of the heart and presence of fluid in the lungs.
• Echocardiogram– A live image of the heart and its contractions on a television screen.
• CAT or MRI scans– Computerised axial tomography or magnetic resonance imaging can show damaged brain tissue in a patient who has had a stroke.

3. Tests to detect causes of secondary hypertension

Tests that may be done to check for causes of possible secondary hypertension, such as kidney artery problems (renovascular disease) or hormonal (endocrine) problems, include:

• Renal and  duplex doppler ultrasound– A test that uses sound waves to detect narrowing of the arteries that supply blood to the kidneys and signs of kidney disease.
• CT or direct renal artery angiogram– Dye is injected and its course followed through the renal arteries to show any narrowing in the arteries.
• Plasma renin activity and aldosterone determination– A blood test that determines the level of renin and aldosterone, hormones that play an important role in blood pressure control.
• VMA and norepinephrine test– The levels of these two hormones are high in certain rare tumours of the adrenal glands that result in hypertension.
• Sleep studies to detect sleep apnoea

Treatment of hypertension – overview

Your doctor will start your treatment according to your risk and your individual compelling indications.
The treatment objectives are:

• To reach blood pressure targets (lower than 140/90 mmHg for people with no major risk factors, co-existing disorders or target organ damage, but 130/80 mmHg for people with major risk factors, diabetes other co-existing disorders, or target organ damage) within three months.
• To limit or prevent additional target organ damage – particularly to the heart, brain, kidneys, blood vessels and eyes.
• To achieve blood pressure control with no or minimal  side effects.
• To decrease the overall cardiovascular risk, not only the blood pressure.
• To find a formulation that provides 24-hour efficacy.
• In order to achieve these objectives, your doctor will compile a full treatment plan, consisting of the following:
• To identify and treat all risk factors, target organ damage and associated conditions
• To escalate treatment if your blood pressure is not controlled to target within three months
• To refer you to a specialist or dietician when needed
• To monitor and re-assess you on a regular basis for blood pressure control, adherence to your medication and drug side effects

Important considerations which will determine your individualised treatment plan, are:

• Socio-economic factors, price and availability.
• The cardiovascular risk factors of the patient.
• The presence of target-organ damage, heart disease or diabetes.
• The presence of other co-existing disorders. This may limit or favour the use of certain drugs.
• The possibility of interactions with drugs used by the patient for other conditions.

Treatment will consist of lifestyle changes for all patients, plus medication (most often starting with more than one drug and progressing to three) for most patients.

In many cases where people have been diagnosed with high blood pressure and they are receiving treatment, the patient’s high blood pressure is not controlled nearly well enough. Less than 30% of treated patients in South Africa are treated to target blood pressure. Another problem area is that other important  risk factors like cholesterol are not being treated, diluting the benefits blood pressure treatment. 

Treatment - lifestyle changes

Although some risk factors for hypertension cannot be controlled, most risk factors for essential hypertension are related to poor health habits and factors which can be controlled by lifestyle modification.

Lifestyle changes should be adopted by ALL people with hypertension. In some cases lifestyle changes may lead to adequate control of hypertension without additional medication. But lifestyle modification is also important for those with other risk factors who do not yet suffer from hypertension. This can delay or prevent development of high blood pressure and heart disease.

In the three tables below, you can view the risk factors and the recommended lifestyle modification or actions at a glance. 

Table 1

Table 2

Table 3

The good news about all these lifestyle factors is that you can do a great deal to improve your health.

For many people, losing weight, exercising regularly, limiting alcohol and sodium and maintaining adequate potassium (3.5 g per day) is enough to lower blood pressure and keep it down. However by 6 months many people revert to their previous unhealthy lifestyle, and in most instances antihypertensive drugs need to be used in conjunction with lifestyle changes. This is particularly relevant to people with a high cardiac risk.

Medication

Although lifestyle changes help, they may not be enough, especially if your blood pressure is markedly elevated and/or you are at high risk. If you can't bring your blood pressure under control by making these changes you may also need to take medication. Lifestyle changes may still reduce the number and doses of medications needed to control hypertension.

The first step in the management of hypertension used to be the use of one drug (usually a diuretic) and the next adding a second drug. But according to the latest data most patients need to be treated with two or even three different antihypertensive drugs from the outset. Increasingly these can be used in a fixed combination or single tablet.

If blood pressure remains >140/90 mm Hg (or >160/90 mmHg in older people) despite the use of three pills (resistant hypertension), a fourth pill may be needed.
The control of blood pressure depends on many factors: heart rate, the force of the pumping action, the volume of blood and the diameter of the blood vessels. Different antihypertensive drugs work on different aspects to lower blood pressure. Your drug prescription will be tailored specifically for you.

It is important to note that if you should take your prescribed antihypertensive medication diligently and should never stop your medication or change the dosage due to undesirable side-effects, or because you feel better. If your doctor has prescribed drugs to control your hypertension, it needs to be controlled on a daily basis. Your hypertension cannot be cured, but it can be controlled, the same way as diabetes can be controlled. If you suffer from unwanted side-effects, discuss this with your doctor. He can prescribe another class of antihypertensive which may work better for you. Finding the right antihypertensive medication for you might mean switching between drugs and finding the best combinations for you.
 

The most important  classes of drugs used in the treatment of high blood pressure include:

• Diuretics– Also known as water tablets, diuretics (hydrochlorthiazide and indapamide used most commonly in South Africa) are often the first line of drug treatment. Diuretics act on your kidneys to help your body eliminate sodium and water. This in turn decreases the pressure within the blood vessels and reduces the workload on the heart. Although diuretics are associated with side effects like erectile dysfunction, gout and weakness, they are cheap and very effective in lowering blood pressure and preventing complications. As soon as the daily dosage reaches 25 mg per day, a second drug will be introduced if blood pressure is still elevated after two months. (Click here for more detailed information on Diuretics)
• Beta and alpha adrenergic blockers– These drugs (Atenolol, Carvedilol, Cardura and others) work by blocking the effects of adrenaline and noradrenaline in your body. Beta blockers lower blood pressure by reducing your heart rate and decreasing the force of contraction of the heart, while alpha blockers dilate the blood vessels. Beta blockers are valuable with cardiac problems, but have reduced stroke protection compared to other antihypertensive drugs, especially in older people. The place of alpha blockers in hypertension is not established, and should generally be used by specialists only. Diuretics and beta blockers should not generally be used in combination because of the risk of diabetes with long term treatment. (Click here for more detailed information on Beta  blockers.)
• ACE inhibitors and angiotensin receptor blockers (ARBs)– Angiotensin converting enzyme (ACE) inhibitors is a dilator (relaxer) of blood vessels. It works by  blocking the formation of the natural body chemical angiotensin II, which constricts blood vessels. However, up to 20% of people who take ACE inhibitors (Capoten, Tritace, Renitec and others) develop a dry, hacking cough. This annoying side effect typically occurs in the 10 to 24 weeks after starting the drug. A small percentage of patients may develop swelling of lips, face and tongue (angioedema) and the Ace inhibitor must be immediately stopped, as this reaction can be fatal. This side effect is more common in black people and those with severe allergies. Some ACE inhibitors can also cause a metallic taste in the mouth. Angiotensin receptor blockers (ARBs) are similar to ACE inhibitors, but it blocks the actions, not the formation of angiotensin II. Therefore it is also a blood vessel relaxer. It blocks angiotensin II directly and  generally do not cause side-effects such as cough or angioedema. Both Ace inhibitors and angiotensin receptor blockers are particularly effective in patients with diabetes and renal disease and combine well with low dose diuretics and calcium channel blockers.
• Direct renin inhibitors- A new class of antihypertensive drugs which will soon ( the launch is scheduled) reach South Africa is a direct renin inhibitor (aliskiren), which blocks the production of angiotensin II by blocking the production of renin. These drugs seem to have fewer side-effects compared with other antihypertensives.
• Calcium channel blockers– These drugs block the entry of calcium into the smooth muscle of the blood vessels, causing them to dilate or relax. Certain types can also slow the heart rate. Long-acting calcium channel blockers such as AdalatXL and Amlodipine (Norvasc, Amloc and others) effectively reduce blood pressure. The short-acting drugs aren't recommended for hypertension because control is erratic and some reports have linked them to adverse health effects. Calcium channels blockers are very valuable drugs and reduce blood in all types of patients with hypertension, and reduce stroke more effectively than other drugs. The most common side effect is swelling of the feet and ankles and is a problem especially in females. Combining the drug with an Ace inhibitor or angiotensin receptor blockers reduces this side effect.
• Centrally-acting drugs- These drugs act on the brain’s mechanisms for controlling blood vessel size.
• The end result is that blood vessels relax and blood pressure decreases. Of the centrally-acting drugs, mainly reserpine, moxonidine and methyldopa are used in clinical practice. Reserpine can be used in uncomplicated hypertension. Methyldopa is specifically recommended for use in pregnancy and is rarely used in other circumstances. It must never be used in patients with impaired liver or kidney function. Moxondine is similar to methyl dopa, but without the same degree of side effects. Useful in patients with metabolic syndrome and resistant hypertension.

Monotherapy versus combination therapy
Patients are usually started on one drug. The expected reduction of blood pressure on monotherapy is 7 – 13 mmHgsystolic, and 4 – 8 mmHg diastolic. In more and more patients such reduction will not be sufficient to restore blood pressure to normal. In fact, studies have also shown that up to 70% of patients seem to need a combination of antihypertensive drugs.

Each drug has an entry level dosage. If the result is not satisfactory, the dosage may be increased or another hypertensive drug added. Combining drugs from different classes has proved to lower blood pressure more effectively than using one drug in higher dosage. When combining different drugs, lower dosages of each can be used. In this way, the possibility of side effects is lower.

Examples of drug combinations:(To be effective, drugs from different classes must be combined to obtain an additive hypotensive effect. Combining drugs with similar side effects must be avoided.)

• Diuretic and beta-blocker
• Diuretic and ACE inhibitor
• Diuretic and angiotensin II antagonist
• Calcium antagonist and beta-blocker
• Calcium antagonist and ACE inhibitor
• Alpha-blocker and beta-blocker

In many cases the drugs are combined in one tablet.

Principles of drug treatment:

• Drug treatment is usually started with one drug, at the lowest dose, to limit side effects.
• If the patient has no side-effects on the drug, but the blood pressure response is inadequate, the dose can be increased.
• However, doctors will often rather add a small dose of a different class of drug, instead of giving a higher dose of the initial drug. Thus an additive hypotensive effect is achieved with minimal side effects.
• Your doctor will not combine drugs that have similar side-effects.
• Doctors try to use long-acting drugs that are effective for 24 hours. This gives more consistent blood pressure control and is more user-friendly for the patient. It may also provide greater protection against cardiovascular events, like heart attack or stroke in the early morning hours.
• Drug treatment must always be combined with the appropriate lifestyle modifications. This may lead to lower dosages of anti-hypertensives, and also a decrease in overall cardiovascular risk and target organ damage.

 Reviewed and updated by Prof Brian Rayner, head of the division of nephrology and hypertension, University of Cape Town and Groote Schuur Academic Hospital, November 2010