Antihypertensives are a class of drugs that are used in the control of elevated (blood) pressure (hypertension) which is an important cardiovascular risk factor. They perform their action thanks to the ability to interfere with the physiological mechanisms that regulate blood pressure.
According to their mechanism of action, antihypertensive drugs are divided into several classes:
- diuretics (amiloride, bumetamide, furosemide, hydrochlorothiazide, chlorthalidone, spironolactone, triamterene)
- beta blockers (atenolol, labetalol, metoprolol, nadolol, propanolol, timolol)
- ACE inhibitors (benazapril, captopril, enalapril, fosinopril, lisinopril, moexipril, quinapril, ramipril)
- angiotensin II receptor antagonists or sartans (olmesartan, irbesartan and losartan)
- calcium channel blockers (amlodipine, diltiazem, felopidine, israpidine, nicardipine, nifedipine, nisoldipine, verapamil)
- alpha blockers (doxazosin, phenoxybenzamine, prazosin, terazosin)
- direct-acting vasodilators acting at the arterial level (minoxidil, hydralazine) or active both arterial and venous (nitroprusside)
Thiazide diuretics. These drugs act on a part of the kidney called the distal tubule, where they block the mechanisms of reabsorption of water and sodium, causing an increase in the quantity of fluid (ultra-filtered) that is eliminated in the urine.Consequently, the volume of blood reaching the heart decreases, as does cardiac output, peripheral resistance and blood pressure. Thiazide diuretics such as hydrochlorothiazide are often the first, but not the only, choice in hypertension medications. They counteract the salt and water retention caused by other drugs that are used to treat high blood pressure (for example l "hydralazine). Therefore thiazides are particularly useful in combination with several other antihypertensive agents including beta blockers and Ace inhibitors (Angiotensin Converting Enzyme, the inhibitors of the angiotensin I to angiotensin II conversion enzyme).
Loop diuretics. These drugs act on a part of the kidney called the loop of Henle. They perform their action by preventing the transport of chlorine and sodium in the ascending part of the loop, thus reducing the reabsorption of water. In addition, they increase the elimination of calcium, magnesium and potassium. They are indicated in the presence of fluid accumulation (edema) and a marked increase in pressure which can cause severe organ damage (usually heart, brain, kidneys, eye ).
Potassium-sparing diuretics. In the kidney they act at the end of the distal tubule and in the collecting duct. These medicines are also called antialdosteronics because they block the effect of a natural chemical substance (hormone), aldosterone, responsible for the retention of salts and liquids, thus favoring the elimination of liquids in the urine (diuresis). They are the only ones able to avoid the loss of potassium (hypokalaemia). These are generally drugs with low diuretic activity, which are used in combination with other diuretics, in particular thiazides, to remedy the loss of potassium caused by these.
Beta-blockers or β-adrenergic antagonists. These are medicines that reduce the workload on the heart because by blocking the action of natural chemicals (hormones) such as adrenaline, they decrease the heart rate. Beta blockers are generally not recommended as the sole drug, but they can be effective when combined with other antihypertensive drugs.
ACE inhibitors or angiotensin converting enzyme inhibitors. These drugs block the formation of a substance, angiotensin, which is responsible for decreasing the diameter of blood vessels (vasoconstriction). In this way, they help to relax the vessels and decrease arterial blood pressure.
Angiotensin II receptor antagonists (ARBs). These drugs help relax blood vessels by blocking the action, not the formation, of angiotensin, the peptide (protein) hormone that stimulates vasoconstriction by increasing blood pressure.
Alpha blockers or α-adrenergic antagonists. These drugs block the effects of natural chemicals (such as adrenaline). They reduce peripheral vascular resistance and relax both venous and arterial smooth muscle.
Direct-acting vasodilators which act at an arterial level or active at both arterial and venous level. These drugs act directly on the muscles in the artery walls, preventing the muscles from contracting and the arteries from narrowing. In this way, resistance is reduced and blood pressure is lowered.
Calcium channel blockers or calcium channel blockers. Calcium channels are involved both in the contraction of heart muscles and in the processes of vasoconstriction of the arteries. Therefore, blocking these channels causes the contraction of vascular smooth muscle to decrease, resulting in a decrease in blood pressure, and a decrease in the workload for the heart.Calcium channel blockers may work better in older people and people of African descent than ACE inhibitors alone do.
In pharmacies, antihypertensives are sold in packs of tablets or suspension to be taken orally, or in the form of solutions for injections that can be administered subcutaneously, intramuscularly or intravenously.
The most recommended classes of antihypertensive agents used as the first line for the treatment of hypertension are:
- diuretics thiazides
- calcium channel blockers
- ACE inhibitors
- angiotensin II receptor antagonists (ARBs)
To reduce the number of daily doses of the drug needed, the doctor may prescribe a low-dose combination of drugs rather than higher doses of a single drug. In fact, two or more antihypertensive drugs are often more effective than just one. One study showed that the reduction in blood pressure is approximately five times greater when drugs of two different classes are combined than when using a double dose of the same drug.
Regarding the quantity and methods of intake, antihypertensive agents must always be prescribed by a doctor and must be used strictly following her instructions. Failure to do so could render the treatment useless or dangerous, even putting your life at risk.
For more information on the active ingredients named in the contribution or in any case belonging to this class of drugs, you can visit the website of the Italian Medicines Agency (AIFA) by clicking HERE. To search for a drug using the trade name and not the active ingredient, you can click HERE. Inside the site you can find all the package leaflets of the drugs and also some additional information. If "revoked" is written next to the drug name, the drug is no longer on the market.
Side effects and contraindications
The intake of antihypertensive drugs can give rise to various side effects depending on the type of drug used. In particular:
- gastrointestinal disorders: nausea, vomiting, diarrhea, abdominal pain
- dermatological disorders: skin rashes, angioedema
- musculoskeletal disorders: muscle and joint pain, muscle cramps
- central disorders: fever, drowsiness, drowsiness, headache, sleep disturbances
- metabolic disorders: liver and kidney dysfunction, decreased potassium concentration (hypokalemia) or magnesium (hypomagnesaemia), increased calcium concentration (hypercalcaemia) and increased uric acid concentration (uricaemia) in the blood
Prescribing antihypertensives during pregnancy and lactation requires careful evaluation of the clinical benefits and potential risks to the mother and baby, and is usually not recommended. Contraindications also exist in the case of patients with heart, kidney and liver diseases and with asthma and diabetes and it is therefore important to always follow the doctor's instructions.
Antihypertensives can interact with other drugs, producing effects other than those expected. Therefore, it is always necessary to ask the attending physician and / or pharmacist for directions and consult the information in the package leaflet.
Khalil H, Zeltser R. Antihypertensive medications. StatPearls [Internet]. 2021; July 26