By Zahra Simpa, DLHA Volunteer and Freelance Writer with editorial support by the Datelinehealth Africa Team.
The burden of Non-communicable diseases (NCDs) is rising steadily and is fast becoming a significant public health threat in Africa. It has been estimated that 41 million people die each year due to NCDs. Some leading NCDs in Africa include hypertension and other cardiovascular diseases, diabetes, and cancers.
In Africa, hypertension is the leading risk factor for cardiovascular diseases like heart failure, heart attack, and stroke. Due to the economic state, not everyone can afford proper treatment and patient education is often lacking.
There are affordable drugs of choice for treating and managing hypertension. However, not all suit everyone because Africans react differently to these drugs.
This article explains the commonly used classes of antihypertensive in Africa and their indications, mechanism of action, possible side effects, cost implications, etc.
Hypertension, also known as the silent killer, is one of Africa's leading causes of death. 1in 4 adults is hypertensive in Nigeria. But most times, people with the condition are not aware of it.
With a population estimate of 399 million by 2050, hypertension levels will increase sporadically. And more than 50% of the population may suffer from different stages of Hypertension.
Due to the economic state of the populace, people often find the best and most affordable antihypertensive drugs to use. One of the most common antihypertensive drugs used in Nigeria is Nifedipine. It is used as a first-line treatment. Interestingly, the specific antihypertensives in use may vary from country to country in Africa (for example, between Nigeria and Ghana)
A first-line treatment means that after lifestyle changes like dieting and exercise fail to manage blood pressure, the drug is the first treatment of choice.
Let's look at the classes of antihypertensive drugs popular in Nigeria.
These drugs act as the first line of treatment for hypertension. They are often used as monotherapy (i.e., just, one drug). However, combination therapy is standard in some patients that fail to react positively to a single antihypertensive drug.
Below are the three most common classes of antihypertensive drugs in Nigeria:
Thiazides are a universal first-line treatment for hypertension regardless of race or age. Thiazides are also known as "water pills." They help remove excess sodium and water from the body as sodium contributes to increased blood pressure. Minimise taking table salt for this reason.
Thiazides support the kidneys in flushing out excess sodium, thereby reducing fluid flow through the veins and arteries. A study has revealed increased sodium retention in Africans compared to other races. The drug has adverse effects in patients with chronic kidney disease.
Thiazide diuretics include:
As mentioned, these drugs are generally used as first-line monotherapy for hypertension treatment. However, your doctor might prescribe another drug in addition to them to improve blood pressure control.
Thiazides are a great choice because they are cheap for their effectiveness in treating hypertension.
Other types of diuretics used in the treatment of hypertension are:
Examples of loop diuretics are:
Examples of potassium-sparing diuretics are:
Since diuretics affect different positions of the kidneys, some pills may contain a combination of two to three diuretics for effectiveness and overall treatments.
Patients suffering from heart failure, other cardiovascular diseases, liver diseases, tissue swelling (oedema), and kidney dysfunctions may find diuretic-type drugs helpful. They tremendously improve symptoms.
Generally, calcium ions increase the excitability of body tissues in the body. Calcium increases contractility, especially in heart muscles.
CCBs are also first-line drugs. However, they are the next drug of choice when patients stop responding to or do not tolerate thiazides.
Calcium channel blockers are the next best drug after thiazides to lower blood pressure in Africans and people of African ancestry without evidence of chronic kidney or heart failure.
CCBs are effective in lowering blood pressure. They are also an affordable treatment option for Africans.
Calcium channel blockers exist in two groups, namely:
Dihydropyridines
These drugs are very efficient in relaxing the muscles of the heart. They are also a preferred choice in treating hypertension.
Dihydropyridines shouldn't be a first-line treatment in people with congestive heart failure.
Rather they should be used as an add-on treatment to control blood pressure and angina pectoris (consistent chest pains).
The most popular CCBs are Nifedipine and Amlodipine. Nifedipine is a more potent antihypertensive drug than Amlodipine.
Non-dihydropyridines
They have minimal effect on relaxing muscles and tissues. They have less antihypertensive action but are more effective in treating arrhythmic (irregular heartbeat) cases.
Prior to 2014, this class of antihypertensive were the least prescribed in Nigeria, but there has been a shift in the last decades towards the use of ACEIs due to the recognition of their heart and kidney protection roles.
They are the first line of drugs for people with chronic kidney failure with an increased protein level in non-black people.
Aside from treating hypertension, they're effective in patients with a high risk of cardiovascular diseases.
The mechanism isn't fully understood. There is little research on the process by which it reduces blood pressure. However, it is known that thiazides act on the kidneys, mainly the distal tubules of the kidneys. The distal tubules possess a high concentration of sodium and potassium. A few weeks into the treatment, thiazides reduce the initial volume of sodium in this tubule. Thiazides also have a decent relaxation effect on the body tissues.
Calcium channel blockers prevent calcium from entering cells. Since calcium causes the heart to squeeze, these drugs allow the heart to relax more and reduce blood pressure. Some are more potent in relaxing the muscles than others. Nifedipine has the highest vasodilator or relaxant effect than other drugs from this class.
ACEIs relax arteries and veins in the heart. They do this by preventing the release of angiotensin II. Angiotensin II is an enzyme that increases blood pressure and causes the narrowing of blood vessels, producing pressure within them.
ARBs block the action of angiotensin II in the body. Doing so expands blood vessels and reduces the heart's workload.
Not everyone can take these drugs. You may have an underlying medical condition that might prevent the drugs from acting adequately and sometimes worsen your condition.
Thiazides: A daily oral dose of 25mg to 100mg is the best form of administration.
Calcium channel blockers: Patients should take 5mg to 10mg daily. Your healthcare provider might increase the dose after 7 to 14 days. Amlodipine is also given at 5mg or 10mg dosage daily. The maximum daily dose for Nifedipine is 120mg.
ACEIS or ARBs: All are given orally except for enalapril which is in IV (intravenous) form.
1. Thiazides
2. Calcium channel blockers
3. ACEIs and ARBs
ACEIs
ARBs
Thiazide diuretics can cause low potassium and sodium levels in the body in the long term. Severe dehydration also occurs.
Non-dihydropyridine can lead to hypotension in severe cases. Dihydropyridine causes hypotension with less effect on heart rate compared to non-dihydropyridines.
ACEIs and ARBs cause lower blood pressure, increased potassium levels, and low sodium concentration.
Thiazide diuretics and calcium blockers are Nigeria's most affordable blood pressure-reducing drugs. But the most used class are ARBs followed by CCBs, then thiazides (diuretics).
The five most used medicines were Losartan, Lisinopril, Nifedipine, Furosemide, and Amlodipine accounting for 74% of the top ten medicines.
More generic antihypertensive products are in use in Nigeria than the branded varieties.
Pregnancy is a crucial period where a woman undergoes various physiological and haematological changes. Hypertension is risky for mothers from pregnancy to postpartum (after delivery). Hypertension causes high mortality in pregnancy.
Calcium channel blockers are an efficient, cost-effective and safe antihypertensive drug for use in pregnancy.
In this case, calcium blockers pose side effects like arrhythmia, Raynaud's syndrome, and cluster headaches when breastfeeding. Nifedipine is suitable for administration in this period. Nimodipine is also a preferred drug choice for cerebrovascular conditions.
Adequate research is lacking and still ongoing in this area. There hasn't been any evidence of infertility in both genders in Africa following the use of antihypertensives.
Subject to appropriate monitoring for side effects and with due awareness of any underlying or co-occuring disorders, ARBs, Calcium Channel Blockers, (CCBs) and Thiazides are the most used blood pressure reducing class of drugs (antihypertensives) in use in Nigeria with the latter two being cheaper. CCBs are also effective for use in pregnancy related high blood pressure conditions as well as during lactation..
Related: Hypertension in Nigerian Adults: Essential things to know.
Published: April 28, 2023
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