Drug treatments for hypertension

While on a visit at my sister-in-law’s place last summer, I met Mrs. Agu, a middle-aged teacher and mother of four. She complained about high blood pressure and wanted me to give her some “abroad” medication to bring down the blood pressure because according to her - “the one they have over there works better than the one they buy from Papa Oke’s chemist store down the street.”

Knowing Nigerians and their incurable habit to exaggerate facts in order to make them more believable and credible, I cautiously asked Mrs. Agu how high this so called blood pressure is. As I rightly suspected, she gave me an exaggerated figure: 280/200 mm Hg. She knows it for a fact because the nurse measured it 2 weeks ago with her home blood pressure device but the medications are too expensive so she bought only two types out of the four recommended by the nurse. The fact is that if her blood pressure was truly that high, she would have ended up either in some ICU or worse still, dead on her way there!

Misconceptions about high blood pressure and its treatment are largely due to poor information or the lack of it. In the Nigerian context, the word ‘hypertension’ is often used in connection with emotional distress but hypertension does not just mean excessive emotional tension, though that can temporarily increase blood pressure. There are both verified and unverified stories of people who suddenly slump and die. And in Nigeria where autopsies are not routine, such deaths are blamed on some jealous neighbour or envious extended family members.

Hypertension, simply put, means high pressure or tension in the arteries that carry blood from the heart to the tissues and organs in the body. It occurs when the blood pressure is above 140/90 mm Hg, measured at least on three different occasions and over a period of three months.

For people suffering from diabetes, kidney diseases or high risk patients for cardio-vascular diseases, it is anything above 130/80 mm Hg.

Proper diagnosis of high blood pressure is important, so efforts can be made to normalize it and also to prevent complications like stroke, kidney diseases, hardening of the arteries, eye damage etc. The recommendation is that at least one hour before blood pressure is taken, one should avoid eating, strenuous exercise, smoking, caffeine intake or other stresses that may alter the blood pressure. General guidelines regarding blood pressure are as follows (mm Hg):

Optimal blood pressure:

< 120/80

Normal blood pressure:

< 130/85

Normal high blood pressure:

<130 – 139/85 – 89

Grade 1 Hypertension:

<140 – 159/90 – 99

Grade 2 Hypertension:

<160 – 179/100 – 109

Grade 3 Hypertension:

> 180/ > 110

The past couple of years have produced an avalanche of drugs that are effective in lowering blood pressure. Some are life saving and most produce prompt results. But they do not cure hypertension, they only control it and in some cases the medication has to be taken for life. These medications target 3 areas or points in the body; the kidneys, the heart and the blood vessels.

The kidneys regulate blood volume. High blood volumes cause the heart to work harder than normal thus increasing the pressure. The kidneys also release an important substance known as rennin which in turn stimulates the production of angiotensin, a hormone that constricts blood vessels and drives blood pressure up. Angiotensin II is the potent direct vasoconstrictor.

ACE-inhibitors & Angiotensin II receptor blockers

The group of drugs known as ACE-inhibitors decreases the production of angiotensin II while Angiotensin II receptor blockers (ARBs) block the action of angiotensin II. As a result, the vessels dilate and blood pressure is reduced making it easier for the heart to pump blood. Examples are Lisinopril®, Cozaar®, Atacand®.

Diuretics

Diuretics (commonly called water pills), are another drug group that help the body to expel excess fluid and salt through the urine thereby lowering blood pressure. There are different kinds of diuretics with effect in different parts of the kidney. Examples are thiazide diuretics such as Esidrix® or loop diuretics such as Frusemide®.

Beta blockers

The muscles of the heart are also affected by the activity of the nerves. Under stressful conditions, certain hormones are released and these send signals via the nerves to the heart to pump both harder and faster thereby increasing pressure. Beta blockers block the effect of these hormones on receptors in the heart and as a result reduce heart rate, and blood pressure. They are best used in combination with other blood pressure medicines in treating high blood pressure. Lowering blood pressure helps to lower the risk of heart disease, heart attack and stroke. Examples include Tenormin®, Seloken®.

Calcium blockers

Blood vessels can become thickened and hardened by plaques. Plaques make the vessels non elastic and slow the flow of blood thus raising blood pressure. Also under stressful conditions, the muscles surrounding the blood vessels tend to contract and become narrower leading to increase in blood pressure and this contraction is aided by calcium. The drug group known as Calcium blockers inhibits the influx of calcium to the muscle cells which cause the muscles to relax. As a result, the blood vessels dilate increasing the supply of blood and oxygen to the heart and lowering blood pressure. Examples include Norvasc®, Plendil®.

Summary:

>> First drug of choice in uncomplicated hypertension is ACE-inhibitor, Thiazide diuretic or Calcium blocker.

>> For diabetic patients or patients with impaired glucose tolerance, the first choice is ACE-inhibitor.

>> ACE-inhibitor can be combined with Thiazide or with Calcium blocker if response is inadequate.

>> Patients who do not tolerate ACE-inhibitor can use ARB

>> Beta blockers are used in special indications or as a complementary treatment in combination with other anti-hypertensive drugs.

References

The Swedish Medical Products Agency (Läkemedelsverket). Goodman and Gilman’s The Pharmacological Basis of Therapeuics. The World of Medicines (LmV). FASS. The Book of Drugs (Läkemedelsboken) 2009/2010. Drugs.com