Antihypertensive agents are drugs that are used in the control of hypertension due to their ability to interfere with the mechanisms that physiologically regulate the pressure. Relative to the different mechanism of action, the antihypertensive drugs can be divided into four groups:
- Drugs that affect the sodium-water balance (diuretics);
- Drugs that act on the functionality of the sympathetic nervous system (sympatholytic);
- Drugs that act on the members of the nerve centers in the control of vascular motility (vasoconstriction and vasodilation);
- Drugs that affect the renin-angiotensin system (hormonal mechanism that regulates blood pressure, total circulating blood volume and tone of the arterial muscles);
The major classes of antihypertensive drugs include:
- Thiazide diuretics (hydrochlorothiazide, chlorthalidone), loop diuretics (furosemide, ethacrynic acid), diuretics that reduce the loss of potassium (amiloride, spironolactone);
- Sympatholytic drugs that act centrally (methyldopa, guanabenz, clonidine);
- Β-adrenergic blockers (propranolol, metoprolol);
- Α-adrenergic antagonists (phenoxybenzamine, prazosin), mixed adrenergic blockers (labetalol), ganglionic blocker (trimetaphan), blockers of adrenergic neurons (guanethidine, betanidina);
- Vasodilators acting directly on the arterial level (minoxidil, hydralazine) or active at both arterial rather than venous levels (nitroprusside);
- Blocking of the channels of calcium or calcium channel blockers (verapamil, nifedipine);
- Agents that affect the renin-angiotensin system or ACE inhibitors (captopril, omapratilat);
- Antagonists of the angiotensin II receptor (or ARBs, such as olmesartan and irbesartan).
How should antihypertensives be taken?
Antihypertensives are commercially available in the form of tablets or suspensions to be taken orally, or in the form of solutions for injection, which may be performed by subcutaneous, intramuscular or intravenous administration.
The antihypertensive agent should always be used on prescription, and strictly following the doctor’s instructions about the dosage and mode of application. Not doing so can reduce the absorption of the drug or render the treatment useless, and even cause a life risk.
Contraindications and warnings associated with the use of antihypertensive agents
The antihypertensive drugs can give rise to several side effects depending on the type of medication used (diuretics, sympatholytic, drugs that act on the nervous centers deputies to the control of the vessel motility, drugs that affect the renin-angiotensin system). In general, however, taking these drugs may cause the following:
- Gastrointestinal disorders: nausea, vomiting, diarrhea, abdominal pain;
- Dermatologic disorders: rash, angioedema;
- Musculoskeletal disorders: muscle and joint aches, muscle cramps;
- Central disorders: fever, lethargy, drowsiness, headache, sleep disorders
- Metabolic disorders: liver and kidney dysfunction.
In cases of pregnancy and nursing, administration of antihypertensive requires careful evaluation of the clinical benefits and potential risks for the mother and unborn child, and it is usually not recommended. Contraindications exist even in cases of patients with heart disease, asthma, kidney disease, liver disease, and diabetes.
