Hypertension sustained systolic blood pressure of greater than 140mm Hg or a sustained diastolic blood pressure which is greater than 90 mm Hg
Both systolic and diastolic blood pressures have a strong relationship with cardiovascular morbidity, mortality and various additional organ complication such as congestive heart failure, renal failure, and peripheral artery disease.
That is also why today hypertension is considered as one of the most important risk factors for cardiovascular diseases due to increases the risk of injury in the vascular beds of various targeted organs such as eyes, brain, heart and kidneys.
The main goal in the treatment of hypertension is not only controlling blood pressure, but also reducing cardiovascular risk. Currently, the therapeutic management of hypertension has advanced both in terms of its efficacy as in its safety and tolerability profiles. It is very important to consider the pathogenic changes of renin secretion, sympathetic tone, and renal sodium excretion, changes in cardiac output, peripheral vascular resistance and blood volume.
Monotherapy for hypertension is not usually able to lower BP to optimal levels in most patients, that’s why combination therapy is used to treat hypertension in patients.
In the treatment of hypertension Diuretic are the first-line therapy unless until there are important factors to choose another drug.
Thiazide are the most widely used oral diuretics used for the treatment of hypertension. Thiazides include:
Thiazide diuretics treats hypertension by counteracting sodium and water retention. These drugs are used in combination with many other drugs such as beta-blockers, ACE inhibitors, ARBs and potassium sparing diuretics.
All thiazide diuretics are active when given orally. Absorption and elimination rate vary. These agents compete with uric acid for their elimination.
Adverse drug reactions may include:
Loop diuretics includes Bumetanide
These drugs lower blood pressure by decreasing arterial resistance and increasing renal blood flow.
The adverse drug reactions may include dizziness, headache, gastrointestinal upset, hypernatremia, hypokalemia, hypercalcemia and dehydration.
These agents include:
Potassium-sparing diuretics acts on the distal parts of the nephron. These agents interfere with sodium reabsorption at the distal tubules, resulting in decreased potassium secretion and more excretion of urine. These drugs also help in cardiac remodelling. Adverse drug reaction may include hyperkalemia, gynecomastia and amenorrhea.
Beta-blockers reduce cardiac output by decreasing arterial blood pressure. Hypertension is usually associated with an increase in blood volume and cardiac output. That’s why, reducing cardiac output by beta-blockade can be an effective for its treatment.
Beta-blockers are orally active. Propranolol under first-pass metabolism.
Beta-blocker may cause bradycardia, fatigue, lethargy, insomnia, decrease HDL and increase plasma triglycerides
ACE inhibitors like enalapril and Lisinopril are recommended as first-line therapy when beta adrenergic blockers are contraindicated.
Ace inhibitors Dilate arteries and veins by blocking angiotensin II formation and inhibiting metabolism of bradykinin. This vasodilation reduces arterial pressure and on the heart. It also down regulate sympathetic adrenergic activity by blocking the effects of angiotensin II on sympathetic nerve release and reuptake of norepinephrine and promotes renal excretion of sodium and water
Side effects of ACE inhibitors include dry cough, hypotension, Angioedema and hyperkalemia
ARBs include the following drugs:
ARBs reduce arterial pressure and preload and afterload on the heart by dilating arteries and veins. By blocking the effects of angiotensin II on sympathetic nerve release and reuptake of norepinephrine It also down regulate sympathetic adrenergic activity and promote renal excretion of sodium and water.
ARBs have a relatively low incidence of side effects because they do not increase bradykinin levels like ACE inhibitors. The dry cough and angioedema that are associated with ACE inhibitors are not a problem with use of ARBs. ARBs are contraindicated in pregnancy. The major side effects includes Angioedema Hypotension, and hyperkalemia.
This class of drugs include:
Renin inhibits are used in hypertension because arterial and venous vasodilation, it also reduces ventricular preload and after load, Decrease blood volume
It is a renin inhibitor which was approved for the treatment of hypertension. It is an orally active nonpeptide drug with a half-life of about 24 hours with once-daily dosing. Aliskiren is metabolized by the liver and excreted by the kidneys.
Aliskiren has dose-related gastrointestinal adverse effects in some patients; diarrhea is observed in less the 3% of patients. Angioedema, hyperkalemia, especially in diabetic patients, non-fatal stroke, renal complications, hyperkalemia, hypotension) are some of common side effects.
There are three different chemical classes of Calcium-Channel Blockers. They differ not only in their their relative selectivity toward cardiac versus vascular calcium channels but also in basic chemical structure.
I – Dihydropyridines
The smooth muscle selective class of Calcium channel Blockers are the dihydropyridines. These drugs are primarily used to reduce systemic vascular resistance and arterial pressure, and that why, are used to treat hypertension because of their high vascular selectivity. Following are the specific drugs that are included in this class:
II – Non-dihydropyridines,
It comprises the other two classes of Calcium channel blockers.
a)- Phenylalkylamine class
This class includes
This drug is less effective as a systemic vasodilator drug and more selective for the myocardium. This drug has a very important role in treating angina by reversing coronary vasospasm and arrhythmias and also by reducing myocardial oxygen demand and
b)- Benzothiazepine class
This class includes
Diltiazem is able to reduce arterial pressure without producing the same degree of reflex cardiac stimulation caused by dihydropyridines, by having both cardiac depressant and vasodilator actions.
Excessive hypotension, edema Constipation, dizziness, flushing, headache and reflex tachycardia are the most common side effects of calcium channel blockers.
The drugs included in this group are
Mechanism of action of hydralazine is not entirely clear and it appears to have multiple, direct effects on the vascular smooth muscle. Hydralazine causes smooth muscle hyperpolarization through the opening of potassium channels. It may also inhibit the release of calcium induced by IP3 from the smooth muscle sarcoplasmic reticulum. This calcium combines with calmodulin to activate myosin light chain kinase, which causes contraction. Finally, hydralazine stimulates the formation of nitric oxide by the vascular endothelium that leads to cGMP-mediated vasodilation.
Minoxidil cause dilation of arterial vessels but not increase capacity of venioles
Common side effects of hydralazine includes flushing, headaches and tachycardia. Some patient also experience a lupus-like syndrome.
Alpha-Adrenoceptors blockers are used in treatment of hypertension and are relatively selective α1-adrenoceptor antagonists. Following drugs are included in this class
These drugs cause the vasodilator effect by dilating both arteries and veins because both vessel types are innervated by sympathetic adrenergic nerves.
The most common side effects are directly related to alpha-adrenoceptor blockage. These side effects include dizziness, orthostatic hypotension, nasal congestion, headache, reflex tachycardia and fluid retention.
Several nitrodilators are available for clinical use:
The nitrodilators differ in the route of administration, onset of action, and duration of action.
Nitroglycerin is commonly used in the treatment of angina because when it is administered sublingually, it is very fast-acting within 2 to 5 minutes.
Isosorbide dinitrate and mononitrate, and tetranitrate drugs have usually a longer onset of action and duration of action than nitroglycerin. For the long-term prophylaxis and management of coronary artery disease, these drugs are more useful than short-acting nitroglycerin. Oral bioavailability of organic nitrates is less because of first-pass metabolism by the liver except Isosorbide mononitrate, which has approximately 100% bioavailability.
Sodium nitroprusside dilates arterial resistance vessels more than venous vessels. It is used to treat severe hypertensive emergencies and severe heart failure due its rapid onset of action,.
Side effects include headache, postural hypotension, cutaneous flushing, and tachycardia. A long term use of sodium nitroprusside has the risk of thiocyanate toxicity because nitroprusside releases cyanide along with Nitric oxide.
There are various centrally acting α2-adrenoceptor agonists are available for clinical use
Centrally acting α2-adrenoceptor agonists block sympathetic activity by binding to α2 adrenoceptors and reduces sympathetic outflow to the heart thereby decreasing cardiac output by decreasing heart rate and contractility. Reduced sympathetic output to the vasculature decreases sympathetic vascular tone, which causes vasodilation and reduced systemic vascular resistance that leads decrease in arterial pressure.
Side effects include sedation, dry mouth and nasal mucosa, bradycardia, orthostatic hypotension, and impotence. Nausea, gastric upset, constipation, fluid retention and edema is also a problem with chronic therapy.
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