Aims of treatment

• To normalise blood pressure.
• To prevent target-organ damage to the heart, brain, kidneys and blood vessels.
• To decrease the overall cardiovascular risk, not only the blood pressure.
• To achieve this with no or minimal side effects.
• To find a formulation that provides 24-hour efficacy.
• To enhance, not replace lifestyle modifications.

Advertisement

Important considerations

• 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.

Major classes of antihypertensive drugs

• Diuretics.
• Beta-Blockers.
• ACE inhibitors.
• Angiotensin II antagonists.
• Calsium antagonists.
• Alfa-Blockers.
• Centrally-acting drugs.

Action of antihypertensive drugs

1. Diuretics
Called “water pills”, it acts on the kidneys to increase elimination of water and salt, thereby reducing blood volume. This in turn decreases the pressure within the blood vessels and reduces the workload on the heart.

Click here for more info on diuretics

2. Beta-Blockers
Slows the heart rate and pumping action of the heart muscle by blocking the action of certain chemicals.

Click here for more info on beta-blockers

3. ACE inhibitors
A dilator (relaxer) of blood vessels. It works by preventing the formation of a powerful blood vessel constrictor, Angiotensin II.

Click here for more info on ACE inhibitors

4. Angiotensin II antagonists
Similar to ACE inhibitors, but it blocks the actions, not the formation of Angiotensin II. Therefore it is also a blood vessel relaxer.

Click here for more info on angiotensin II receptor blockers

5. Calcium channel blockers
Blocks the entry of calcium into the smooth muscle of the blood vessels, causing it to dilate or relax. Certain types can also slow the heart rate.

Click here for more info on calcium channel blockers

6. Alpha-Blockers
Alpha blockers inhibit the effect of norepinephrine, a hormone that causes constriction of blood vessels. In this way, the arteries dilate and blood pressure decreases.

Click here for more info on alpha-blockers

7. Centrally-acting drugs
These drugs act on the brain’s mechanisms for controlling blood vessel size.

Click here for more info on centrally-acting drugs

Monotherapy versus combination therapy
Patients are usually started on one drug. The expected reduction of blood pressure on monotherapy is 7 – 13 mmHg systolic, and 4 – 8 mmHg diastolic. For some patients such reduction will not be sufficient to restore blood pressure to normal.

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. Studies have also shown that up to 70 % of patients seem to need a combination of antihypertensive drugs. 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.
• Alfa-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. This way 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.

Written by Dr Kathleen Coetzee, MBChB.

Read more:
Risk factors you can't control
Changing your lifestyle

Rate this article Poor 1 2 3 4 5 Excellent

JOBS

Senior Secretary Gauteng - North/Sandton Infrastructure Resource Gauteng - Johannesburg Management Accountant R450,000-500,000 Per Annum Cost To Company Gauteng - Johannesburg Financial Manager R350,000-400,000 Per Annum Cost To Company Gauteng - Johannesburg Financial and Project Accountant R300,000-360,000 Per Annum Cost To Company Gauteng - Johannesburg Financial Accountant R380,000-420,000 Per Annum Cost To Company Gauteng - Johannesburg SSIS Business Intelligence Specialists (SSIS; SSAS) R350,000-500,000 Per Annum Cost To Company Gauteng - North/Sandton Financial Accountant R350,000-450,000 Per Annum Cost To Company Gauteng - South Find more jobs Register your CV Post a job