Drugs for Hypertension 17 Drugs for Hypertension

Directory Classroom Response System Lecture Note Presentation

Question 1 Which of the following is not a nonpharmacologic method of controlling hypertension?

Question 1 Choices Weight loss Smoking cessation Moderate exercise Decreased potassium and magnesium intake

Question 1 Answer Weight loss Smoking cessation Moderate exercise Decreased potassium and magnesium intake

Question 2 An otherwise healthy man has been diagnosed with hypertension. You suspect that the physician will order:

Question 2 Choices Hydrochlorothiazide (Microzide) Captopril (Capoten) Nifedipine (Adalat, Procardia) Enalapril (Vasotec)

Question 2 Answer Hydrochlorothiazide (Microzide) Captopril (Capoten) Nifedipine (Adalat, Procardia) Enalapril (Vasotec)

Question 3 The patient is on two antihypertensive drugs. The nurse recognizes that the advantage of multidrug treatment is:

Question 3 Choices Blood pressure decreases faster. Adverse effects are fewer and patient adherence is greater. There is less daily medication dosing. Multidrug therapy treats the patient’s other medical conditions.

Question 3 Answer Blood pressure decreases faster. Adverse effects are fewer and patient adherence is greater. There is less daily medication dosing. Multidrug therapy treats the patient’s other medical conditions.

Question 4 The patient is taking furosemide (Lasix) 40 mg bid. The patient should be monitored for:

Question 4 Choices Hyperkalemia Hypokalemia Hypernatremia Hypercalcemia

Question 4 Answer Hyperkalemia Hypokalemia Hypernatremia Hypercalcemia

Learning Outcomes Explain how hypertension is defined. Summarize the long-term consequences of untreated hypertension. Describe how the pumping action of the heart creates blood pressure. Explain the effects of cardiac output, peripheral resistance, and blood volume on blood pressure.

Learning Outcomes Discuss how the vasomotor center, baroreceptors, emotions, and hormones influence blood pressure. Discuss the role of therapeutic lifestyle changes in the management of hypertension. Describe general principles guiding the pharmacotherapy of hypertension.

Learning Outcomes For each of the classes listed in the Drug Snapshot, identify representative medications and explain the mechanism of drug action, primary actions, and important adverse effects.

Core Concept 17.1 Hypertension is defined as the consistent elevation of arterial blood pressure.

Hypertension Consistent elevation of arterial blood pressure Rarely made on a single blood pressure measurement Diagnosis made: Sustained systolic blood pressure of greater than 140 mm Hg

Hypertension Or diastolic pressure of greater than 90-99 mm Hg after multiple measurements are made over several clinic visits.

Core Concept 17.2 Failure to treat hypertension can lead to stroke, heart failure or myocardial infarction.

Hypertension Primary/Essential No specific cause Risk Factors Advancing age Weight gain, particularly around the hips & thighs

Hypertension Primary/Essential Blacks Men Hereditary component, Tobacco use High-fat diets

Secondary Hypertension Certain diseases Cushing’s syndrome Hyperthyroidism Chronic renal disease

Secondary Hypertension Certain drugs Corticosteroids Oral contraceptives Erythropoietin (epoetin alfa) Therapeutic goal Treat or remove the underlying condition

Blood pressure is caused by the pumping action of the heart. Core Concept 17.3 Blood pressure is caused by the pumping action of the heart.

Pumping Action of the Heart Pressure can be measured in nearly any vessel in the body Commonly refers to the pressure in the arteries.¥ Pumping action of the heart is the source of blood pressure

Pumping Action of the Heart Arteries closest to the heart, such as the aorta, have the highest pressure. Pressure decreases gradually as the blood travels farther from the heart, until it falls close to zero in the largest veins

Figure 17.1 Blood pressure changes throughout the circulation

Blood Pressure Systolic pressure Diastolic pressure The ventricles of the heart contract and eject blood Diastolic pressure The ventricles relax The heart temporarily stops ejecting Blood pressure in the arteries will fall

Blood Pressure Measured in units of millimeters mercury, abbreviated as mm Hg.

Figure 17.2 (a) Systolic pressure occurs when the heart ejects blood, creating high pressure in the arteries. (b) Diastolic pressure occurs when the heart relaxes, resulting in less pressure in the arteries.

Core Concept 17.4 The primary factors responsible for blood pressure are cardiac output, the resistance of the small arteries, and blood volume.

Cardiac Output The volume of blood pumped per minute Resting cardiac output is approximately 5 liters per minute (L/min) Strenuous exercise can increase this output to as much as 35 L/min

Cardiac Output Drugs that change the cardiac output have the potential to influence a patient’s blood pressure higher the cardiac output, the higher the blood pressure.

Peripheral Resistance Blood flows at high speeds through the vascular system Bumps and drags across the walls of the vessels Friction reduces the velocity of the blood

Blood Volume Total amount of blood in the vascular system Average person maintains a relatively constant blood volume of approximately 5 L Change with

Blood Volume Certain regulatory factors Certain disease states More blood in the vascular system will exert additional pressure on the walls of the arteries and raise blood pressure.

Figure 17.3 Primary factors affecting blood pressure

Core Concept 17.5 Many nervous and hormonal factors help to keep blood pressure within normal limits.

Figure 17.4 Blood pressure is controlled by the actions of the cardiovascular system and kidneys.

Figure 17.5 Hormonal and nervous factors influencing blood pressure

Concept Review 17.1 Because hypertension may cause no symptoms, how would you convince a patient to take his or her medication regularly?

Core Concept 17.6 Positive lifestyle changes can reduce blood pressure and lessen the need for medications.

Life Style Changes Implement a medically supervised, safe weight-reduction plan, if 20% or more over normal body weight. Stop using tobacco. Restrict salt (sodium) intake, and eat foods rich in potassium and magnesium.

Life Style Changes Limit alcohol consumption. Implement a medically supervised aerobic exercise plan. Reduce sources of stress and learn to implement coping strategies.

Core Concept 17.7 Selection of specific antihypertension drugs depends on the severity of the disease.

Goal of Therapy The goal of antihypertensive therapy is to reduce blood pressure to normal levels so that the long-term consequences of hypertension may be prevented

Figure 17.6 Mechanism of action of antihypertensive drugs

Primary Antihypertensive Agents Diuretics Renin-angiotensin-aldosterone inhibitors Calcium channel blockers (CCBs) Beta-adrenergic blockers

Core Concept 17.8 Diuretics are often drugs of first choice for treating mild to moderate hypertension.

Actions of Diuretic Increase the amount of urine produced by the kidneys. Widely used in the treatment of hypertension and heart failure. Reduce blood volume through the urinary excretion of water and electrolytes Mechanisms of actions differ

Electrolyte Imbalance Loss of potassium, sodium, and magnesium Loss of potassium, or hypokalemia Can lead to serious abnormalities in cardiac rhythm Thiazide or loop diuretics

Concept Review 17.2 State the major reasons why patients should continue lifestyle changes even though their antihypertensive drugs appear to be effective.

Core Concept 17.9 Calcium channel blockers have emerged as important drugs in the treatment of hypertension.

Calcium Channel Blockers Group of about 10 drugs Used to treat a number of cardiovascular diseases Angina pectoris Cardiac dysrhythmias HTN.

Mechanism of Action Contraction of a muscle regulated by amount of calcium ion inside muscle cell Contraction occurs when calcium enters the cell through channels in the plasma membrane

Mechanism of Action CCBs block these channels prevent Ca+2 from entering the cell Inhibits muscular contraction At low doses cause vasodilation in arterioles Decreases blood pressure

Mechanism of Action Some CCBs are selective for calcium channels in arterioles Others affect channels in both arterioles and cardiac mus

Core Concept 17.10 Blocking the renin-angiotensin-aldosterone system leads to a decrease in blood pressure.

Renin-Angiotensin-Aldosterone System (RAAS) One of the primary homeostatic mechanisms controlling blood pressure and fluid balance in the body Drugs that modify the RAAS decrease blood pressure and increase urine volume. Block angiotensin II, thus decreasing blood pressure through two mechanisms: dilating arteries and decreasing blood volume.

Table 17.5 (continued) ACE Inhibitors and Angiotensin-Receptor Blockers Used for Hypertension

Core Concept 17.11 Alpha- and beta-adrenergic blockers are commonly used to treat hypertension.

Alpha and Beta Blockers Blocking the sympathetic “fight or flight” responses Drugs can cause the heart rate to slow, blood pressure to decline and the bronchi to dilate

Alpha and Beta Blockers Actions Blockade of alpha1 receptors in the arterioles Blockade of beta1 receptors in the heart Nonselective blockade of both beta1 and beta2 receptors Stimulation of alpha2-adrenergic receptors in the brainstem (centrally acting)

Table 17.6 (continued) Adrenergic Blockers and Central-Acting Agents Used for Hypertension

Concept Review 17.3 Why is it important for the patient to weigh himself or herself on a regular basis when taking antihypertensive drugs?

Core Concept 17.12 Vasodilators lower blood pressure by relaxing arteriolar smooth muscle.

Vasodilators Affect vascular smooth muscle highly effective at lowering blood pressure Not drug of first choice Many adverse effects Direct vasodilators produce reflex tachycardia Normal physiological response to sudden decrease in blood pressure

Vasodilators Forces the heart to work harder, blood pressure increases, counteracting the effect Sodium and water retention Kidney retains more sodium and water, blood volume increases, raises blood pressure