1. Antihypertensive Drugs
Chapter 22
Antihypertensive Drugs
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Blood Pressure
Blood pressure = CO × SVR
CO = cardiac output
SVR = systemic vascular resistance
Hypertension = high blood pressure
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Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC-7)*
Four stages, based on BP measurements
Normal
Prehypertension
Stage 1 hypertension
Stage 2 hypertension
*New guidelines pending
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Classification of BP
Hypertension can also be defined by its cause
Unknown cause
Essential, idiopathic, or primary hypertension
90% of cases
Known cause
Secondary hypertension
10% of cases
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6. Classroom Response Question
The number of people with hypertension in the United States is estimated to be:
10 million.
50 million.
75 million.
100 million.
Correct answer: B
Rationale: As many as 50 million people in the United States have some form of hypertension, which makes it the most common disease in the population of the Western hemisphere.
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7. Autonomic Nervous System
Parasympathetic nervous system
Stimulates smooth muscle, cardiac muscle, glands
Sympathetic nervous system
Stimulates the heart, blood vessels, skeletal muscle
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8. Location of the Nicotinic Receptors in the PNS and SNS
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9. Antihypertensive Drugs
Medications used to treat hypertension
Categories
Adrenergic drugs
Angiotensin-converting enzyme (ACE) inhibitors
Angiotensin II receptor blockers (ARBs)
Calcium channel blockers (CCBs)
Diuretics
Vasodilators
Direct renin inhibitors
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11. Adrenergic Drugs: Five Subcategories
Centrally and peripherally acting adrenergic neuron blockers
Centrally acting alpha2 receptor agonists
Peripherally acting alpha1 receptor blockers
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12. Adrenergic Drugs: Five Subcategories (cont’d)
Peripherally acting beta receptor blockers (beta blockers)
Cardioselective (beta1 receptors)
Nonselective (both beta1 and beta2 receptors)
Peripherally acting dual alpha1 and beta receptor blockers
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Adrenergic Drugs
Centrally acting alpha2 receptor agonists
Stimulate alpha2-adrenergic receptors in the brain
Decrease sympathetic outflow from the CNS
Decrease norepinephrine production
Stimulate alpha2-adrenergic receptors, thus reducing renin activity in the kidneys
Result in decreased blood pressure
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14. Adrenergic Drugs (cont’d)
Centrally acting alpha2 receptor agonists (cont’d)
clonidine (Catapres)
methyldopa (Aldomet)
Can be used for hypertension in pregnancy
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15. Adrenergic Drugs (cont’d)
Peripheral alpha1 blockers/antagonists
Block alpha1-adrenergic receptors
doxazosin (Cardura)
terazosin (Hytrin)
prazosin (Minipress)
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16. Adrenergic Drugs (cont’d)
Beta blockers
Reduce BP by reducing heart rate through beta1 blockade
Cause reduced secretion of renin
Long-term use causes reduced peripheral vascular resistance
Examples: nebivolol (Bystolic), propranolol (Inderal), atenolol (Tenormin), others
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17. Adrenergic Drugs (cont’d)
Dual-action alpha1 and beta receptor blockers
Reduce heart rate (beta1 receptor blockade)
Cause vasodilation (alpha1 receptor blockade)
carvedilol (Coreg) and labetalol
Result in decreased blood pressure
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18. Adrenergic Drugs: Indications
All used to treat hypertension
Centrally acting alpha2 receptor agonists
Treatment of hypertension, either alone or with other drugs
Usually used after other drugs have failed because of adverse effects
Clonidine is useful in the management of withdrawal symptoms in opioid-dependent persons
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19. Adrenergic Drugs: Indications (cont’d)
Peripherally acting alpha1 receptor agonists
Treatment of hypertension
Some used to relieve symptoms of BPH
tamsulosin (Flomax)
Management of severe heart failure (HF) when used with cardiac glycosides and diuretics
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20. Adrenergic Drugs: Adverse Effects
High incidence of orthostatic hypotension
Most common
Bradycardia with reflex tachycardia
Dry mouth
Drowsiness, sedation
Constipation
Depression
Edema
Sexual dysfunction
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21. Adrenergic Drugs: Adverse Effects (cont’d)
Other
Headaches
Sleep disturbances
Nausea
Rash
Cardiac disturbances (palpitations), others
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22. Classroom Response Question
When administering an alpha-adrenergic drug for hypertension, it is most important for the nurse to assess the patient for the development of:
hypotension.
hyperkalemia.
oliguria.
respiratory distress.
Correct answer: A
Rationale: These drugs have strong vasodilating properties and may cause severe hypotension, especially at the beginning of therapy.
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23. Angiotensin-Converting Enzyme (ACE) Inhibitors
Large group of safe and effective drugs
Often used as first-line drugs for HF and hypertension
May be combined with a thiazide diuretic or calcium channel blocker
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24. ACE Inhibitors (cont’d)
captopril (Capoten)
benazepril (Lotensin)
enalapril (Vasotec)
fosinopril (Monopril)
lisinopril (Prinivil)
moexipril (Univasc)
quinapril (Accupril)
Others
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25. ACE Inhibitors: Mechanism of Action
Inhibit angiotensin-converting enzyme, which is responsible for converting angiotensin I (through the action of renin) to angiotensin II
Angiotensin II is a potent vasoconstrictor and causes aldosterone secretion from the adrenal glands
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26. ACE Inhibitors: Mechanism of Action (cont’d)
Block angiotensin-converting enzyme, thus preventing the formation of angiotensin II
Prevent the breakdown of the vasodilating substance bradykinin
Result in decreased systemic vascular resistance (afterload), vasodilation, and therefore decreased blood pressure
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27. ACE Inhibitors: Indications
Hypertension
HF (either alone or in combination with diuretics or other drugs)
Slow progression of left ventricular hypertrophy after MI (cardioprotective)
Renal protective effects in patients with diabetes
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28. Classroom Response Question
A patient with type II diabetes has a new prescription for the angiotensin-converting enzyme (ACE) inhibitor lisinopril. She questions this order because her physician has never told her that she has hypertension. What is the best explanation for this order?
The doctor knows best.
The patient is confused.
This medication has cardioprotective properties.
This medication has a protective effect on the kidneys for patients with type II diabetes.
Correct answer: D
Rationale: ACE inhibitors have been shown to have a protective effect on the kidneys because they reduce glomerular filtration pressure. This property makes them the cardiovascular drug of choice for diabetic patients.
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29. ACE Inhibitors: Indications (cont’d)
Drugs of choice in hypertensive patients with HF
Drugs of choice for diabetic patients
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30. Classroom Response Question
A patient with a history of pancreatitis and cirrhosis is also being treated for hypertension. Which drug will most likely be ordered for this patient?
clonidine
prazosin
diltiazem
captopril
Correct answer: D
Explanation: Captopril is not a prodrug; therefore it does not need to be metabolized by the liver to be effective. This is an advantage in patients with liver disease.
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31. ACE Inhibitors (cont’d)
Captopril and lisinopril are NOT prodrugs
Prodrugs are inactive in their administered form and must be metabolized in the liver to an active form so as to be effective
Captopril and lisinopril can be used if a patient has liver dysfunction, unlike other ACE inhibitors that are prodrugs
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32. ACE Inhibitors: Adverse Effects
Fatigue
Dizziness
Headache
Mood changes
Impaired taste
Possible hyperkalemia
Dry, nonproductive cough, which reverses when therapy is stopped
Angioedema: rare but potentially fatal
Note: First-dose hypotensive effect may occur
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33. Angiotensin II Receptor Blockers
Also referred to as angiotensin II blockers or ARBs
Well tolerated
Do not cause a dry cough
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34. Angiotensin II Receptor Blockers
losartan (Cozaar)
eprosartan (Teveten)
valsartan (Diovan)
irbesartan (Avapro)
candesartan (Atacand)
olmesartan (Benicar)
telmisartan (Micardis)
azilsartan (Edarbi)
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35. 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 vasoconstriction and release of aldosterone
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36. Angiotensin II Receptor Blockers: Indications
Hypertension
Adjunctive drugs for the treatment of HF
May be used alone or with other drugs such as diuretics
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37. Angiotensin II Receptor Blockers: Adverse 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
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38. Classroom Response Question
Which statement about angiotensin II receptor blockers does the nurse identify as being true?
Hyperkalemia is more likely to occur than when using ACE inhibitors.
Cough is more likely to occur than when using ACE inhibitors.
Upper respiratory infection is a common adverse effect.
Overdose is usually manifested by hypertension and bradycardia.
Correct answer: C
Rationale: Angiotensin II receptor blockers have the common adverse effect of upper respiratory infection. Hyperkalemia and cough are less likely to occur than when using ACE inhibitors and overdose of angiotensin II receptor blockers is manifested by hypotension and tachycardia.
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39. Calcium Channel Blockers: Mechanism of Action
Cause smooth muscle relaxation by blocking the binding of calcium to its receptors, preventing muscle contraction
Results in:
Decreased peripheral smooth muscle tone
Decreased systemic vascular resistance
Decreased blood pressure
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40. Calcium Channel Blockers: Indications
Angina
Hypertension
Dysrhythmias
Migraine headaches
Raynaud’s disease
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Diuretics
Decrease plasma and extracellular fluid volumes
Results
Decreased preload
Decreased cardiac output
Decreased total peripheral resistance
Overall effect
Decreased workload of the heart and decreased blood pressure
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Diuretics (cont’d)
Thiazide diuretics are the most commonly used diuretics for hypertension
Listed as first-line antihypertensives in the JNC-7 guidelines
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Vasodilators
diazoxide (Hyperstat)
hydralazine HCl (Apresoline)
minoxidil (Loniten)
sodium nitroprusside (Nipride, Nitropress)
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44. Vasodilators: Mechanism of Action
Directly relax arteriolar and/or venous smooth muscle
Results in:
Decreased systemic vascular response
Decreased afterload
Peripheral vasodilation
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45. Vasodilators: Indications
Treatment of hypertension
May be used in combination with other drugs
Sodium nitroprusside and intravenous diazoxide are reserved for the management of hypertensive emergencies
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Nursing Implications
Before beginning therapy, obtain a thorough health history and head-to-toe physical examination
Assess for contraindications to specific antihypertensive drugs
Assess for conditions that require cautious use of these drugs
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47. Nursing Implications (cont’d)
Educate patients about the importance of not missing a dose and taking the medications exactly as prescribed
Instruct patients to check with their physician for instructions on what to do if a dose is missed; patients should never double up on doses if a dose is missed
Monitor BP during therapy; instruct patients to keep a journal of regular BP checks
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48. Nursing Implications (cont’d)
Instruct patients that these drugs should not be stopped abruptly because this may cause a rebound hypertensive crisis, and perhaps lead to 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
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49. Nursing Implications (cont’d)
Remind patients that medication is only part of therapy. Encourage patients to watch their diet, stress level, weight, and alcohol intake
Instruct patients to avoid smoking and eating foods high in sodium
Encourage supervised exercise
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50. Nursing Implications (cont’d)
Teach patients to change positions slowly to avoid syncope from postural hypotension
Instruct patients to report unusual 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
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51. Nursing Implications (cont’d)
Male patients who take these drugs may not be aware that impotence is an expected effect, and this may influence compliance with drug therapy
If patients are experiencing serious adverse effects, or if they believe the dose or medication needs to be changed, they should contact their physician immediately
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52. Nursing Implications (cont’d)
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 over-the-counter drugs, without first getting the approval of their physician
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53. Nursing Implications (cont’d)
Educate patients about lifestyle changes that may be needed
Weight loss
Stress management
Supervised exercise
Dietary measures
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54. Nursing Implications (cont’d)
Monitor for adverse effects (dizziness, orthostatic hypotension, fatigue) and for toxic effects
Monitor for therapeutic effects
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