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2011-07-20 12:12:14
Antihypertensive Agents

Antihypertensive agents
Show Answers:

  1. Blood pressure = CO x SVR
    • cardiact output
    • systemic vascular resistance
  2. Hypertension is
    High blood pressure
  3. Four stages, based on BP measurements
    • -Normal
    • -Prehypertension
    • -Stage 1 hypertension
    • -Stage 2 hypertension
  4. Classification and management of blood pressure
  5. Classification of BP
    • Hypertension can also be defined by its cause
    • -Unknown cause-Essential, idiopathic, or primary hypertension, 90% of the cases
    • -Known cause- Secondary hypertension, 10% of the cases
  6. Compelling indications
    • -Post-MI
    • -High cardiovascular risk
    • -Heart failure
    • -Diabetes mellitus
    • -Chronic kidney disease
    • -cerebrovascular disease
  7. JNC-7: Significant changes
    • -High diastolic BP (DBP) is no longer considered to be more dangerous than high systolic BP (SBP)
    • -Studies have shown that elevated SBP is strongly associated with heart failure, stroke, and renal failure.
    • -For those older than age 50, SBP is a more important risk factor for cardiovascular disease (CVD) than DBP
    • -"Prehypertensive" BPs are no longer considered "high normal" and require lifestyle modifications to prevent CVD.
    • -Thiazide-type diuretics should be the initial drug therapy for most patients with hypertension (alone or with other drug classes)
    • -The previous labels of "mild", "moderate", and "severe" have been dropped.
  8. Cultural Considerations
    • -Beta-blockers and ACE inhibitors have been found to be more effective in Caucasians patients than African American patients.
    • -CCBs and diuretics have been shown to be more effective in geriatric and African American patients than in Caucasian patients.
  9. Non-Pharmacologic Treatment
    • -Diet and Exercise
    • -Limit alcohol consumption
    • -Reduce sodium intake
    • -Smoking cessation
  10. Antihypertensive Agents: Categories
    • -Adrenergic agents
    • -Angiotensin converting enzyme (ACE) inhibitors
    • -Angiotensin II receptor blockers (ARBs)
    • -Calcium channel blockers (CCBs)
    • -Diuretics
    • -Vasodilators
  11. Site and mechanism of action for various antihypertensive agents.
  12. Adrenergic Agents
    • -Centrally and peripherally acting adrenergic neuron blockers
    • -Centrally acting alpha2-receptor agonists
    • -Peripherally acting alpha1-receptor antagonists
    • -Peripherally acting beta-receptor blockers (beta blockers)-both cardioselective (beta1-receptors) and nonselective (noth beta1 and beta2-receptors)
    • -Peripherally acting dual alpha1-and beta receptor blockers
  13. Location of the nicotinic receptors within the parasympathetic and sympathetic nervous systems.
  14. Adrenergic agents: Mechanism of action
    • -Centrally and peripherally stores in neurotransmitters storage vesicles
    • -SNS is not stimulated (beta-receptors in the heart and alpha1-receptors in blood vessels)
    • -Result: decreased blood pressure.
  15. Centrally and peripherally action neuron blocker
    • -Resperine
    • -The only centrally and peripherally acting neuron blocker still available in the U.S.
  16. Adrenergic Agents: Mechanism of action
    • -Centraly acting alpha2-receptor agonists
    • -stimulate alpha2-adrenergic receptors in the brain
    • -Sympathetic outflow from the CNS is decreased
    • -Norepinephrine production is decreased
    • -Result: decreased blood pressure
  17. Adrenergic Agents: Centrally acting alpha2-receptor agonists
    • -clonidine (catapres)
    • clonidine patch (catapres-TTS)
    • -guanfacine (Tenex)
    • -methyldopa (aldomet) -drug of choice for hypertension in pregnancy
  18. Adrenergic Agents: Mechanism of Action
    • -Preipherally acting alpha1-receptor antagonists.
    • -Block the alpha1-adrenergic receptors
    • -The SNS is not stimulated
    • -Result: decreased blood pressure
    • -stimulation of alpha1-adrenergic receptors cause hypertension
    • -Blocking alpha1-adrenergic receptors causes decreased blood pressure
  19. Adrenergic Agents: Peripherally acting alpha1-receptor antagonists
    • -Doxazosin (cardura)
    • -Prazosin (minipress)
    • -Terazosin (hytrin)
  20. Adrenergic Agents Indications
    • -Adrenergic neuronal blockers (centrally and peripherally acting neuron blocker)
    • -Treatment of hypertension, either alone or with other agents.
    • -seldom used because of frequent side effects
    • -Centrally acting alpha2-receptor agonists
    • -Treatment of hypertension, either alone or with other agents
    • -Usually used after other agents have failed due to side effects.
    • -Centally acting alpha2-receptor agonists
    • -Also may be used for treatment of severe dysmenorrhea, menopausal flushing, glaucoma
    • -Clonidine is useful in the management of withdrawal symptoms in opioid- or nicotine- dependent persons.
    • -Peripherally acting alpha1-receptor antagonists
    • -Treatment of hypertension
    • -Relief of symptoms of BPH
    • -Management of severe HF when used with cardiac glycosides and diuretics
  21. Adrenergic Agents Side effects
    • Most common: dry mouth, drowsiness, sedation, constipation
    • Other: Headaches, sleep disturbances, nausea, rash, cardiac disturbances (palpations)
  22. Adrenergic Agents- Beta Blockers
    • -Act in the periphery
    • -Reduce heart rate due to beta1-blockade
    • -Examples: Propranolol (inderal), atenolol (tenormin), metoprolol (Lopressor), metoprolol-extended release (Toprol XL)
  23. Adrenergic Agents -Dual alpha1-and beta-receptor blockers
    • -Act in the periphery at heart and blood vessels
    • -Reduce heart rate (beta1-receptor blockade)
    • -Cause vasodilation (alpha1-receptor blockade)
    • -Excamples: labetalol (Normodyne,Tandate),carvdilol(Coreg)
  24. Angiotensin Converting Enzyme Inihibitors (ACE inhibitors, or ACEIs)
    • -Large group of safe and effective drugs
    • -Often used as first-line agents for HF and hypertension
    • -May be combined with a thiazide diuretic or calcium channel blocker
  25. Ace inhibitors: Mechanism of Action
    • RAAS: renin angiotensin-aldosterone system
    • -When the enzyme angiotensin I is converted to angiotensin II, the result is potent vasconstriction and stimulation of aldosteron.
    • -Result of vasoconstriction: increased systemic vascular resistance and increased afterload
    • result: increased BP
    • -Aldosteron stimulates water and sodium resorption
    • -Result: increased blood volume, increased preload, and increased BP
    • -ACE inhibitors block the angiotensin converting enzyme, thus preventing the formation of angiotensin II
    • -Also prevent the breakdown of the vasodilating substance, bradykinin
    • -Result: decreased systemis vascular resistance (afterload), vasodilation, and therefore decreased blood pressure.
  26. ACE inhibitors: Indications
    • -Hypertension
    • -HF (either alone or in cobination of diuretics or other agents)
    • -Slows progression of left ventricular hypertrophy after an MI
    • -Renal protective effects in patients with diabetes
    • -Drugs of choice in hypertensive patients with HF
    • -captopril (Capoten)- very short half life
    • -enalapril (Vasotec)- Available in oral and parenteral forms
    • -lisinopril (Prinivil and Zestril) and quinapril (Accupril)- Newer agents, long half-lives, once a day dosing
    • -Several other agents available
  27. ACE Inhibitors : Side efftects
    • -Fatigue, headache, impaired taste, dizziness, mood changes, possible hyperkalemia, dry, nonproductive cough, which reverses when therapy is stopped
    • NOTE: First-dose hypotensive effect may occur!!
  28. Angiotensin II Receptor Blockers
    • -( A II blockers, or ARBs)
    • -Newer class
    • -Well tolerated
    • -Do not cause a dry cough
  29. Angiotensin II Receptor Blockers: Mechanism of Action
    • -Allow angiotensin I to be converted to angiotensin II, but block the receptors that receive angiotensin II
    • -Block vasconstriction and release of aldosterone
  30. Angiotensin II Receptor Blockers
    • -Isartan (Cozaar, Hyzaar)
    • -valsartan, (Diovan)
    • -candesartan (Atacand)
  31. Angiotensin II Receptor Blockers: Indications
    • -Hypertension
    • -Adjunctive agents for the treatment of HF
    • -May be used alone or with other agents such as diuretics
    • -Used primarily in patients who cannot tolerate ACE inhibitors
  32. Angiotensin II Receptor Blockers: Side Effects
    • -Upper respiratory infections
    • -Headache
    • -May cause occasional dizziness, inability to sleep, diarrhea, dyspnea, heartburn, nasal congestion, back pain, fatigue
    • -Hyperkalemia much less likely to occur
  33. Calcium Channel Blockers: Mechanism of Action
    • -Cause smooth muscle relaxation by blocking the binding of calcium to its receptors, preventing muscle contraction
    • -This causes decreased peripheral smooth muscle tone and decreased systemic vascular resistance
    • -Result: decreased blood pressure
  34. Calcium Channel Blockers
    -Benzothiazepines - diltiazem (Cardizem, Dilacor)

    -Phenylalkamines- verapamil (Calan, Isoptin)

    -Dihydropyridines- amlodipine (Norvasc), nicardipine (Cardene) nifedipine (Procardia), nimodipine (Nimotop)
  35. Calcium Channel Blockers : Indications
    • -Angina
    • -Hypertension
    • -Dysrhythmias
    • -Migraine headaches
    • -Raynaud's disease
  36. Calcium Channel Blockers: Side Effects
    • -Cardiovascular- Hypotension, palpitations, tachycardia
    • -Gastrointestinal- Constipation, nausea
    • -Other- Rash, flushing, peripheral edema, dermatitis
    • -Decrease the plasma and extracellular fluid volumes
    • -Results: Decreased preload, decreased cardiac output, decreased total peripheral resistance
    • -Overall effect: Decreased worload of the heart, and decreased blood pressure.
  38. Vasodilators: Mechanisms of Action
    • -Directly relax arteriolar smooth muscle
    • -Result: decreased systemic vascular response, decreased afterload, and peripheral vasodilation
  39. Antihypertensive Agents Vasodilators
    • -diazoxide (Hyperstat)
    • -hydralazine HCl (Apresoline)
    • -minoxidil (Loniten,Rogaine)
    • -sodium nitroprusside (Nipride, Nitropress)
  40. Vasodilators: Indications
    • -Treatment of hypertension
    • -May be used in combination with other agents
    • -Intravenous sodium nitroprusside and diazoxide are reserved for the management of hypertensive emergencies.
  41. Vasodilators: Side Effects
    -Hydralazine-Dizziness, headache, anxiety, tachycardia, nausea, and vomiting, diarrhea, anemia, dyspnea, edema, nasal congestion

    -Sodium nitroprusside- Bradycardia, hypotension, possible cyanide toxicity.
  42. Nursing Implications
    • -Before beginning therapy, obtain a thorough health history and head to toe physical examination
    • -Assess for contraindications to specific antihypertensive agents
    • -Assess for conditions that require cautious use of these agents
    • -Educate patients about the importance of not missing a dose and taking the medications exactly as prescribed
    • -Patients should never double up on doses if a dose is missed; check with the physician for instruction on what to do if a dose is missed
    • -Monitor BP during therapy; instruct patients to keep a journal of regular BP checks
    • -Instruct patients that these drugs should be stopped abruptly because this may cause a rebound hypertensive crisis, and perhaps lead to a stroke
    • -Oral forms should be given with meals so that absorption is more gradual and effective.
    • -Administer IV forms with extreme caution and use an IV pump
    • -Remind patients that medication is only part of therapy. Encourage patients to watch their diet, stress level, weight, and alcohol intake.
    • -Patients should avoid smoking and eating food high in sodium
    • -Encourage supervised exercise
    • -Instruct patients to change positions slowly to avoid syncope from postural hypotension
    • -Patients should report unsual shortness of breath; difficulty breathing; swelling of the feet, ankles, face, or around the eyes; weight gain or loss; chest pain; palpitations; or excessive fatigue
    • -Men takign theses agents may not be aware that impotence is an expected effect. This may influence compliance with the drug therapy
    • -If patients are experincing serious side effects, or believe that t he dose or medication needs to be changed, they should contact their physician immediately
    • -Hot tubs, showers, or baths; hot weather; prolonged sitting or standing; physical exercise; and alcohol ingestion may aggravate low blood pressure, leading to fainting and injury. Patients should sit or lie down until symptoms subside.
    • -Patients should not take any other medications, including OTC drugs, without frist getting the approval of their physician.
    • -Educate about lifestyle change that may be needed
    • -Weight loss
    • -Stress management
    • -supervised exercise
    • -Monitor for side/adverse effects (dizziness,orthostatic hypotension, fatigue) and for toxic effects
    • -Monitor for therapeutic effects - BP should be maintained at less than 140/90mm hg
    • -If a patient with hypertension also has diabetes or renal disease, the BP goal is <130/80 mm hg