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CHAPTER 26

CHAPTER 26. Antihypertensive Drugs. BP control. Sympathetic tone – constant low level sympathetic stimulation RAA system – Renin – angiotensin - aldostrone system. Hypertension. Hypertension is the leading cause of cardiovascular disease and mortality

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CHAPTER 26

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  1. CHAPTER 26 Antihypertensive Drugs

  2. BP control • Sympathetic tone – constant low level sympathetic stimulation • RAA system – Renin – angiotensin - aldostrone system

  3. Hypertension • Hypertension is the leading cause of cardiovascular disease and mortality • Disease symptoms and organ damage caused by hypertension are not evident until 10–15 years after the disease has started • Proper medication and patient compliance will control most cases of hypertension

  4. Classes of Hypertension • Normotensive <120 / <80 • Prehypertension 120-139 / 80-89 • Stage 1 (mild) 140-159 / 90-99 • Stage 2 (severe) >160 / >100 • Malignant >210 / >150 • BP >140 / >90 REQUIRES DRUG THERAPY

  5. Causes of Hypertension • Most people have essential hypertension where the exact cause is not known (90%) - essential • Increased sympathetic activity and sodium overload increase blood pressure (BP) • Renal disease and increased renin-angiotensin- aldosterone activity raise BP and cause sodium and fluid retention (RAA system) • Smoking, body overweight, and increased sodium consumption contribute to hypertension

  6. Conservative Rx • Sodium restriction • Weight loss • Stop smoking • Exercise • Reduce stress / relaxation techniques

  7. Drug Classes Used to Treat Hypertension • Diuretics • Sympatholytic drugs • Vasodilator drugs • Calcium antagonist drugs • Angiotensin-converting enzyme inhibitor and angiotensin receptor blocking drugs

  8. Diuretic Therapy • Diuretics increase sodium excretion and relax arterial blood vessels (vasodilatation) • Thiazides are preferred in patients with adequate renal function • Organic acid diuretics (loop diuretics) are used in patients with reduced renal function • Diuretics can be used alone or in combination with other antihypertensive drugs • Excessive loss of fluid, sodium, and potassium are common adverse effects

  9. Diuretics • Reduce blood volume • Reduce Na+ concentration in vessel wall-decreases ability to respond to sympathetic stimulation

  10. Sympathetic Blocking Drugs • Alpha blockers lower BP by vasodilatation • Beta blockers lower BP by decreasing heart rate and cardiac output • Centrally acting sympatholytic drugs decrease the activity of the cardiovascular centers in the medulla oblongata • Review the pharmacology of these drugs in chapter 6 • Hence: reduce hyperactive Sympathetic NS

  11. Sympathetic Blockers • Central – reduce NE release • Clonidine (Catapres) • Methyldopa (Aldomet) • Alpha blockers – vasodialator • (Minipress) • Beta blockers – Block β1 in heart • ↓ cardiac output • Block renin release

  12. Beta blockers Β1 blockers reduce cardiac output – pulse rate & force of contraction Propranolol (Inderal)

  13. Vasodilator Drugs • Vasodilators decrease the muscular tone and contractile function of blood vessels • Hydralazine and minoxidil are potent vasodilators that must be used with diuretics and sympathetic blocking drugs • Minoxidil causes hirsutism and is sold topically for treatment of baldness

  14. Calcium Antagonists • Block the influx of calcium into the heart and arterial blood vessels • Verapamil (Calan) and diltiazem (Cardizem) act on both the heart and blood vessels to lower BP • Nifedipine (Prcardia) and other calcium blockers lower BP only by vasodilation • Calcium antagonists are also used to treat angina pectoris and cardiac arrhythmias

  15. Angiotensin-Converting Enzyme Inhibitors (ACEIs) • ACEIs inhibit the formation of angiotensin which is a potent vasoconstrictor • ACEIs decrease the release of aldosterone which retains sodium and water • The ACEIs can be used with thiazide and organic acid diuretics, but not potassium-sparing diuretics • These drugs produce a low incidence of adverse effects and do not interfere with mental activity or renal function

  16. Angiotensin Receptor Blockers • These drugs block angiotensin receptors on blood vessels and adrenal cortex • Like the ACEIs, these drugs produce vasodilatation and decrease the activity of aldosterone • The angiotensin receptor blockers generally produce a lower incidence of adverse effects than the ACEIs

  17. ACE inhibitors • Enalopril (Vasotec) – blocks ACE • ARB – angiotensin receptor blocker • Block angiotensin II receptors • Block vasoconstriction • Block aldosterone secretion • Losartin (Cozaar)

  18. Treatment of Hypertensive Crisis • Severe hypertension is a medical emergency that can lead to stroke and sudden death • Immediate Parenteral administration of antihypertensive drugs can avoid severe complications and irreversible damage • Diazoxide and nitroprusside are potent vasodilators used in hypertensive crisis

  19. Patient Education • Hypertension is a chronic disease that usually requires lifelong treatment • Patients must be instructed to take their medications exactly as prescribed • Healthful living with weight control, exercise, elimination of smoking, and stress can help keep blood pressure under control

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