Drugs Affecting BP

8/13/2019 Drugs Affecting BP

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Copyright 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins

Chapter 28Drugs Affecting Blood Pressure


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Physiology The heart is composed of four chambers: the left

atrium, the right atrium, the left ventricle, and theright ventricle.

The two phases of the cardiac cycle are:systole and diastole.

Contractions of the heart propel blood through thevessels

The formula for measuring blood pressure is:Blood pressure = cardiac output peripheralresistance

BP = CO PR:


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Regulation of Blood Pressure


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Role of Adrenergic Receptors

Adrenergic receptors affect blood pressure causing aSympathomimetic effect

Sympathomimetic effect (one that mimics the effect of thesympathetic system).

Alpha-1 receptors :

Stimulated peripheral constriction

(blood pressure increases)

Blocked dilates arterioles and veins

( blood pressure drops)


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Alpha-2receptor sites are located within the brain

Stimulation inhibits sympathetic system

(sympathetic outflow from the CNS)

Results in : heart rate, vasoconstriction


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Beta-1 receptor sites located in the heart

Stimulation- heart rate

speed of conduction

force of contraction

Blockingcauses the opposite effect,


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Beta 2 receptors are in the:

bronchial and vascular musculatue

Stimulation causes :

bronchial and peripheral dilation



Role of Renin-Angiotensin-AldosteroneSystem

Another mechanism involved in blood pressure regulationis the renin-angiotensin-aldosterone system.

Renin,which is synthesized by the kidneys, producesangiotensin I.

Angiotensin I is an inactive substance until it isconverted to the active angiotensin II

Angiotensin II is a potent vasoconstrictor.

{It also stimulates secretion of aldosterone from theadrenal medulla}



Pathophysiology

In the United States, hypertension is a chronic disorderthat affects all age groups.

Hypertension is common in all racial groups, {althoughsome groups are more prone to hypertension thanothers}.

The American Heart Association defines adult

hypertension as :persistent elevation of 140/90 mm Hg.



Classification of Hypertension



Lifestyle Modification and Hypertension

In prehypertension, therapy usually consists of lifestylechanges,which include reducing weight and adopting theDietary Approaches to Stop Hypertension (DASH).

DASH recommends a diet rich in fruits, vegetables, and nonfatdairy, along with reduced intake of saturated and total fat, buthigher potassium and calcium intake.

Lifestyle modifications also include: limiting alcohol intake,regular exercise, and stopping smoking.

Lifestyle changes also are believed to be essential inpreventing hypertension.

Lifestyle modification remains an important aspect of therapyfor patients in stage 1 or stage 2 hypertension. Lifestylemodifications may decrease the required drug therapy dosage.



Angiotensin-Converting EnzymeInhibitors (ACE inhibitors)

In the renin-angiotensin-aldosterone sequence, a specialenzyme is needed to convert the inactive angiotensin I to theactive angiotensin II.

Angiotensin II is a potent vasoconstrictor. Its presenceincreases secretion of aldosterone.

The ACE inhibitors prevent the conversion of angiotensin I toangiotensin II.

ACE inhibitors are used as first-line antihypertensives if thepatient has comorbidities.

Prototype drug: captopril (Capoten)



Captopril: Core Drug Knowledge Pharmacotherapeutics

Hypertension, Congestive Heart failure, diabeticnephropathy, and left ventricular dysfunction.

Pharmacokinetics

Administered: Oral ( rapid onset of action)

Metabolism: liver. Excreted: kidneys.

Pharmacodynamics Inhibits the ACE(enzyme) needed to change the

inactive angiotensin I to the active form angiotensinII.

Decreasing Angiotensin II decreases aldosteronesecretion {which prevents Na and H2O retention}



Captopril: Core Drug Knowledge (cont.)

Contraindications and precautions

2nd and 3rd trimester of pregnancy (cause injury tothe fetus) {Black Box Warning category D }

- Hypersensitivity and cross sensitivity with other ACEinhibitors

Adverse effects

Persistent nonproductive cough, rash, hypotension

Hyperkalemia ; Hyponatremia

Drug interactions

Several drugs



Captopril: Core Patient Variables Health status

Assess blood pressure before starting therapy.

Life span and gender

Determine pregnancy status.

Lifestyle, diet, and habits

Assess normal dietary habits

Environment

Assess environment where drug will be given.

Culture and inherited traits

Assess patients ethnic and cultural background.

{smaller antihypertensive response in African Americans than

Caucasions}


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Captopril: Planning & Interventions

Maximizing therapeutic effects

Administer captopril 1 hour before mealsbecause food decreases absorption.

Minimizing adverse effects

Monitor the patient for at least 2 hours afterthe initial dose and until blood pressurestabilizes.

Assess lab values for:

hyperkalemia, hyponatremia, neutropenia, proteinuria.



Captopril: Teaching, Assessment &Evaluations

Patient and family education

Teach purpose of drug therapy and any adversereactions.

Teach signs and symptoms to report.

Ongoing assessment and evaluation

Monitor blood pressure throughout captopril therapy.

Blood pressure that decreases to a normal range isindicative of successful drug therapy.



Angiotensin II Receptor Blocker

Losartanis the prototype drug ( a monopotassium salt)

Pharmacotherapeutics used to treat hypertension

Pharmacokinetics- has a high first pass metabolism

converted in liver to an active metabolite

highly protein bound

Pharmacodynamics- inhibits the pressor effect of

Angiotensin II by preventing binding to receptor sites



Angiotensin II Blocker

Contraindications - hypersensitivity to the drug

Pregnancy Category C 1sttrimester

Pregnancy Category D 2nd, 3rdtrimester

{ Black Box warning for this}

Maximimize Therapeutic Effect-

does not cause the cough that ACE inhibitors do

Adverse effects hypotension, dizzyness, fatigue,diarrhea, upper respiratory infections



Angiotensin II Blocker

Drug Interactions lithium, rifampin and indomethacin

{ if taken with K or K sparing medications can cause

increased K levels}

Food Interactions grapefruit juice may drugeffectiveness

Core Patient Variables- not for use in patients with

severe congestive heart failure

Increases in BUN / creatinine in the elderly

If hepatic disease; give lower starting dose

Safety and efficacy in children < 18 yrs of age unknown



Angiotensin II Receptor Blocker

Minimize adverse effects help the patient out of bed

Nursing diagnosis :

Risk for injury related to fall, secondary to adverseeffect of dizzyness

Desired outcome :patient will not fall

Provide Patient and Family Education related to :

dizzyness pregnancy category

caution with OTC drugs upper respiratory infection


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Alpha-Beta Blockers

Alpha Beta Blocker:

slow heart rate

decrease cardiac output

lower blood pressure.

Prototype drug: labetalol (Normodyne)


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Labetalol: Core Drug Knowledge

Pharmacotherapeutics

Treatment of hypertension.

Pharmacokinetics

Administered: oral.

Peak: 2-4 hours. Crosses the bloodbrain barrier.

Pharmacodynamics Adrenergic non specific blocking agent at:

the beta-1 and beta-2 receptor sites

selective alpha-1 blocking action.


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Labetalol: Core Patient Variables

Health status

Assess for the underlying pathology of the hypertension.

Life span and gender

Assess age; safety has not been established inchildren.


Assess lifestyle changes.

Environment

Assess environment where drug will be given.


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Labetalol: Nursing Diagnoses andOutcomes

Decreased Cardiac Output related to effect of drugtherapy

Desired outcome:the patient will not developdecreased cardiac output substantial enough to altercardiac perfusion.

Risk for Injury related to orthostatic hypotension

secondary to adverse effects of drug therapy Desired outcome:the patient will not sustain injury

if transient orthostatic hypotension develops.


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Labetalol: Planning & Interventions


Administer oral labetalol with food to increaseabsolute bioavailability.


Prepare IV infusions of labetalol carefully.

Observe the patient closely for signs of heart failure.

Monitor closely the blood pressure of patientsreceiving IV infusions of labetalol.


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Labetalol: Teaching, Assessment &Evaluations

Patient and family education

Explain the purpose of the drug.

Explain the importance of not stopping drug therapyabruptly.

Ongoing assessment and evaluation

Monitor blood pressure throughout labetalol therapy.


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Question

Labetalol is contraindicated for the treatment ofhypertension in which of the following patients?

A. 23 y/o male with diabetes mellitus type I

B. 55 y/o female how just had her third heart attack

C. 34 y/o male with history of bronchial asthma

D. 75 y/o female with congestive heart failure


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Rationale

Labetalol is contraindicated for the treatment ofhypertension in which of the following patients?

C. 34 y/o male with history of bronchial asthma

Labetalol blocks both beta-1 and beta-2 stimulation.The result of blocking beta-2 stimulation isbronchoconstriction. For that reason, labetalol would

not be given to a patient with asthma.


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Hydralazine: Core Drug Knowledge

Direct acting vasodilators Hydralazine(prototype)

Pharmacotherapeutics

Adjunct to other antihypertensives.

Pharmacokinetics

Absorbed: orally. Peak: 1 to 2 hours. Metabolized:liver. Excreted: kidneys.

Pharmacodynamics

Produces direct smooth muscle relaxation of thearterioles peripheral resistance BP


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Hydralazine: Core Drug Knowledge (cont.)

Contraindications and precautions

Hypersensitivity, CAD, and mitral valvular disease

Adverse effects

Arthralgia, dermatoses, fever, splenomegaly, andglomerular nephritis

Drug interactions

Metoprolol, propranolol, furosemide, andindomethacin


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Hydralazine: Core Patient Variables

Health status

Blood pressure and drug history.

Life span and gender Pregnancy category C.


Explore lifestyle modification.

Environment Assess environment where drug will be given.

Culture and inherited traits

Assess genetic background.


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Hydralazine: Nursing Diagnoses andOutcomes

Ineffective Therapeutic Regimen Management related toadverse effects of drugs

Desired outcome:the patient will not experienceadverse effects severe enough to stop drug therapy.


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Hydralazine: Planning & Interventions


Administering hydralazine with food promotes

bioavailability.


Administer hydralazine with a beta blocker(preferably) or clonidine to decrease reflex

tachycardia and with a diuretic to offset fluidretention.

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Drugs Affecting BP