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Chapter 28 - Drug Therapy for Hypertension

Terms in this set (16)

Overview of Hypertension
HTN increases risks of MI, heart failure, cerebral infarction & hemorrhage, & renal disease

Arterial BP reflects the force exerted on arterial walls by blood flow

Two major determinants: cardiac output (systolic) & peripheral vascular resistance (diastolic)

Body tissues have ability to regulate their own blood flow (autoregulation)
Factors affects HTN
Cardiac output equals the product of the heart rate & stroke volume (CO = HR x SV).

Stroke volume is the amount of blood ejected with each heartbeat (approx. 60-90 mL).

Cardiac output depends on the force of myocardial contraction, blood volume, & other factors.

Peripheral vascular resistance is determined by local blood flow & the degree of constriction or dilation in arterioles & arteries.

The endothelial cells that line blood vessels produce vasoactive substances (constrict or dilate).
Clinical Manifestations of HTN
Primary (essential) or secondary HTN

Early on, no symptoms occur; some cases mild

Often discovered after damage has occurred

Severe HA, N/V, visual disturbances, neurologic disturbances, disorientation, & decreased LOC
Angiotensin-converting enzyme (ACE) inhibitors
Captopril (Capoten) is the prototype

Block the enzyme that normally converts angiotensin I to angiotensin II (potent vasoconstrictor)

Decrease vasoconstriction & decrease aldosterone production

Beneficial in diabetic pts.: helps reduce proteinuria & delay kidney damage
Adverse Effects & Contraindications of ACE Inhibitor (Captopril)
Low incidence of serious adverse effects

Persistent cough may develop ("ACE" cough)

Acute hypotension & hyperkalemia may occur

Contraindications: pregnancy, known hypersensitivity, or angioedema with previous ACE inhibitor
Nursing Implications of ACE Inhibitor (Captopril)
Many medications interact
* Salt substitutes can increase risk of hyperkalemia

Should take 1 hour before or 2 hours after meals

Monitor BP

Instruct childbearing age women to take measures to prevent pregnancy while taking ACE inhibitors
Angiotensin II Receptor Blockers (ARB)
Resemble ACE inhibitors in effects on BP

Less likely to cause hyperkalemia

Losartan (Cozaar) is the prototype

Drug's metabolite is 40x more potent (responsible for duration of action)

Blocks vasoconstriction & aldosterone secreting effects

Increases renal flow
Use of ARB (Lo-sartan)
HTN
Diabetic neuropathy
Maximal effects occur in 3 to 6 weeks
May be ineffective in African Americans when used alone
Adverse Effects of ARB (Lo-sartan)
Generally well tolerated
Dizziness
muscle cramps
weakness
heartburn
diarrhea
some reports of angioedema
Other Drugs in Class of ARB
Cande-sartan (Atacand)
Irbe-sartan (Avapro)
Olme-sartan (Benicar)
Telmi-sartan (Micardis)
Val-sartan (Diovan)
Adjuvant Medications used to treat HTN
Direct Renin Inhibitor

Antiadrenergics
Direct Renin Inhibitor
Aliskiren (Tekturna) is prototype
Only direct renin inhibitor
Antiadrenergics
Inhibit activity of the SNS

Alpha 1 adrenergic receptor blockers
* Dilate blood vessels & peripheral vascular resistance
* Adverse effect: first-dose phenomenon-results in orthostatic hypotension, with palpitations, & dizziness
* Another effect: leads to Sodium & Fluid retention
Beta-adrenergic blockers
1st choice for patients older than 50

Decrease heart rate, force of myocardial contraction, cardiac output, & renin release
Calcium Channel Blockers
Used for several cardiovascular disorders

For HTN, drug dilates peripheral arteries & decrease peripheral vascular resistance
Diuretics
For mild to moderate HTN, diuretics often 1st line drug

For moderate to severe HTN, must add antihypertensive

Thiazide, loop, or potassium-sparing diuretics may used
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