Antihypertensives
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Transcript of Antihypertensives
Antihypertensives are a class of drugs that are usedto treat hypertension (high blood pressure).
Antihypertensive therapy seeks to prevent the complications of high blood pressure, such as stroke and myocardial infarction.
Classes Diuretics
Adrenergic receptor antagonists Benzodiazepines
Calcium channel blockers Renin Inhibitors ACE inhibitors
Angiotensin II receptor antagonists Aldosterone receptor antagonists
Vasodilators α2 agonists
Endothelin receptor blockers
• Hydrochlorothiazide, a popular thiazide diuretic
• Loop diuretics:– Furosemide
• Thiazide diuretics:• Thiazide-like diuretics:• Potassium-sparing diuretics:– spironolactone
Diuretics
ActionAct on kidney
Relax blood vessel walls
Remove more sodium and water from water
Lower blood pressure
• Thiazide diuretics are recommended as the first line of treatment for high blood pressure. They are usually recommended as one of at least two medicines to control high blood pressure.
• Loop diuretics are prescribed for people who also have heart failure, kidney problems, or swelling in their legs (edema)
• Furosemide, like other loop diuretics, acts by inhibiting NKCC2, the luminal Na-K-2Cl symporter in the thick ascending limb of the loop of Henle.
• By inhibiting the transporter, the loop diuretics reduce the reabsorption of NaCl and also diminish the lumen-positive potential that derives from K+ recycling
• Spironolactone is used primarily to treat heart failure, edematous conditions such as nephrotic syndrome or ascites in patients with liver disease, essential hypertension, hypokalemia.
• spironolactone is only a weak diuretic because it primarily targets the distal nephron (collecting tubule), where only small amounts of sodium are reabsorbed, but it can be combined with other diuretics to increase efficacy.
• The antihypertensive effect of spironolactone may exceed that of complex combined regimens of other antihypertensives since it targets the primary cause of the elevated blood pressure.
Adrenergic receptor antagonists
• Beta blockers– atenolol–Metoprolol
• Alpha blockers
• Mixed Alpha + Beta blockers:– labetalol
Beta Blocker
s
Inhibits the effect of nor
epinephrine and epinephrine
And lessens the feedback mechanism
G protein receptor kinase inhibits
receptor activity
Increase in cyclic Adenosine
monophosphate
Improves contractions
Decrease heart rate, Calcium
entry into failing myocytes
Labetalol combines both selective, competitive, alpha-1-adrenergic blocking and nonselective, competitive, beta-adrenergic blocking activity in a single substance.
Stimulation of beta receptors
within myocardium
Stimulation of alpha receptors within vascular smooth muscles
Decrease in systemic arterial blood pressure and systemic
vascular resistance
Without a reduction in heart rate, cardiac output or stroke
volume.
Benzodiazepines
• They work as an agonist of the GABA-a receptors in the brain, thus slowing down neurotransmission and dilating blood vessels.
• benzodiazepines inhibit the re-uptake of a nucleoside chemical called Adenosine, which serves as an inhibitory chemical mentioned above. It also serves as a coronary vasodilator, allowing the cardiac muscle to relax and dilating cardiac arteries.
Calcium channel blockers
• block the entry of calcium into muscle cells in artery walls.
Peripheral arterial dilatation
Stimulation of renin and formation of angiotensin
Decrease systemic vascular resistance
Decrease in blood pressure
AmlodipineNifedipineDiltiazem
Diltiazem• Diltiazem is a potent vasodilator, increasing blood flow and variably decreasing the heart rate via strong depression of A-V node conduction.
• Because of its negative inotropic effect, diltiazem causes a modest decrease in heart muscle contractility and reduces myocardium oxygen consumption.
• Its negative chronotropic effect results in a modest lowering of heart rate, due to slowing of the sinoatrial node. It results in reduced myocardium oxygen consumption.
• Because of its negative dromotropic effect, conduction through the AV (atrioventricular) node is slowed, which increases the time needed for each beat. This results in reduced myocardium oxygen consumption
Renin InhibitorsRenin inhibitors bind to
the active site of renin and inhibit the binding of renin to
angiotensinogen. renin inhibitors prevent the formation of Ang I and
Ang II A reduction in Ang II levels or blockade of angiotensin receptors
suppress the feedback loop
increased plasma renin concentrations (PRC) and plasma renin activity(PRA)
ACE Inhibitors
Blocks the conversion of angiotensin I to angiotensin II
Lower arteriolar resistance
Increase venous capacity
Normally Angiotensin II causes vasoconstriction and hence
hypertension.
Decrease cardiac output
Increase excretion of sodium in the urine
Stimulates adrenal gland to release aldosterone which causes sodium retention and hence increase in blood
pressure.
Stimulates post. Pituitary to release vasopressin which also increases water
retention
With ACE inhibitors, the production of angiotensin II is decreased, leading to decreased blood pressure.
CaptoprilEnalaprilRamipril
Angiotensin II receptor antagonists
These substances are AT1-receptor antagonists; that is, they block the activation of angiotensin II AT1 receptors. vasodilatation.
reduces secretion of vasopressin.
reduces production and secretion of aldosterone.
The combined effect reduces blood pressure.
olmesartantelmisartan
Vasodilators• Vasodilators act directly on the smooth muscle of arteries to relax their walls so blood can move more easily through them; only used in hypertensive emergencies.
Vasodilatation works to decrease TPR and blood pressure through
relaxation of smooth muscle cells in the tunica media layer of large arteries and smaller
arterioles.
TPR: total peripheral resistance
α2 agonists
Stimulate alpha receptors in the brain
Open peripheral arteries
For treating hypertension, these drugs are usually administered in combination with a diuretic.
Adverse effects of this class of drugs include sedation, drying of the nasal mucosa and rebound hypertension.
Endothelin receptor blockers
By blocking this interaction, bosentan decreases pulmonary vascular resistance.
Under normal conditions, endothelin-1 binding of ET-A or ET-B receptors causes constriction of the pulmonary blood vessels.
Bosentan is a competitive antagonist of endothelin-1 at the endothelin-A (ET-A) and endothelin-B (ET-B) receptors.
Side Effects of Diuretics
Potassium-sparing diuretics retain the potassium that other diuretics cause the body to excrete. Common side effects of these diuretics include nausea, headache and stomach upset.
The most common side effect of loop diuretics, such as Lasix, is hypokalemia, or low potassium.
Other side effects include dry
mouth, weakness, diarrhea and headache.
difficulty urinating, gout, and hives are severe side effects and should be addressed immediately.
Thiazide diuretics can cause orthostatic hypotension.
Side Effects of ACE Inhibitors
Common side effects of ACE inhibitors are diarrhea, headache and joint pain.Fever and chills, trouble breathing or jaundice requires immediate attention.
May include fatigue, dizziness and weakness.
Side Effects of Beta Blockers
Regular check-Up