Adrenergic Blocking Drugs

Adrenergic Blocking Drugs
Chapter 18

I Adrenergic blocking
A. opposite effect of agonist adrenergic drugs.
B. antagonists: bind to receptors and inhibit/block stimulation by the SNS.
C. AKA sympatholytics because they lyse/inhibit SNS stimulation.
II Alpha blockers
A. block a1 and a2 receptors
B. effects:
1. both arterial and venous dilation reducing peripheral vascular resistance and bp
2. used to treat HPN
3. on prostate gland and bladder decreased resistance to urinary outflow, thus reducing urinary obstruction and relieving effects of BPH (benign prostatic hyperplasia)
4. used to control and prevent hypertension in pts with pheochromocytoma
5. phentolamine is a blocker that (counteracts):
a. quickly reverses the potent vasoconstrictive effects of extravasated vasopressors such as norepinephrine or epinephrine.
(infiltrated vasopressors will stop blood flow and kill tissues)
b. restores blood flow and prevents tissue necrosis (death)
C. side effects:
1. cardiovascular:
a. palpitations
b. orthostatic hypotension
c. tachycardia
d. edema
e. dysrhythmias
f. chest pain
2. CNS
a. dizziness
b. headache
c. drowsiness
d. anxiety
e. vertigo
f. weakness
g. numbness
h. fatigue
3. gastrointestinal
a. nausea
b. vomiting
c. diarrhea
d. constipation
e. abdominal pain
4. other
a. incontinence
b. nosebleed
c. tinnitus
d. dry mouth
e. pharyngitis
f. rhinitis
D. Common agents
1. phentolamine (regitine)
2. prazosin (minipress)
3. tolazoline (priscoline)
E. Contraindications
1. known drug allergy
2. peripheral vascular disease
3. may include: hepatic and renal disease, CAD, peptic ulcer, sepsis
III Beta Blockers
A. block stimulation of beta 1 & 2 receptors in the SNS
B. compete with norepinephrine and epineprhine
C. 2 types
1. selective aka cardioselective: Beta 1 blocker selective for those on receptors on the heart are called cardioselective
2. nonselective aka nonspecific blockers are effective on both b1 and b2 receptors
D. Mechanism of action
1. cardioselective (b1)
a. reduces SNS stimulation of the heart
b. decreases heart rate
c. prolongs SA node recovery
d. slows conduction rate through the AV node
e. decreases myocardial contractility, thus decreasing myocardial o2 demand.
***. a and b for b/p
b, c, d, for afib
a and d for heart failure(congestive), heart attack (post MI), and angina
2. nonspecific (b1 and b2)
a. effects on heart: same as cardioselective
b. effects on bronchioles: constriction resulting in narrowing of the airways and SOB
c. blood vessels: vasoconstriction
E. Indications
1. antiangina: decreases demand for myocardial o2
2. cardioprotective: inhibits stimulation from circulating catecholamines
3. class II antidysrhythmic
4. anthi HPN
5. treatment of migraine headaches
6. glaucoma (topical use)
F. Side effects
1. blood
a. agranulocytosis
b. thrombocytopenia (decreased platelets)
2. cardiovascular
a. av block
b. bradycardia
c. heart failure
d. peripheral vascular insufficiency
3. CNS
a. dizziness
b. mental depression
c. lethargy
d. hallucinations
e. impotence
4. gastrointestinal
a. nausea
b. dry mouth
c. vomiting
d. diarrhea
e. cramps
f. ischemic colitis
5. other
a. impotence
b. rash
c. alopecia
d. bronchospasm
G. Common agents
1. atenolol (tenormin) selective
2. carvedilol (coreg) selective beta, & alpha
3. labetalol (trandate) same as above
4. sotalol (betapace)
5. metoprolol (lopressor) selective
6. propranolol (inderol) nonselective
7. Newer beta blockers with once a day dosing:
a. betazolol
b. besoprolol

Nursing Implications

I Assess
A. allergies
B. history of COPD
C. hypotension
D. cardiac dysrhythmias
E. bradycardia, HF, or other CV problems
F. any preexisting condition that might be exacerbated by the use of these agents might be a contraindication to their use.

Alpha blockers may precipitate hypotension.

Some beta blockers may precipitate bradycardia, hypotension, heart block, HF and bronchoconstriction.

Avoid OTC meds bc of possible interactions.
Possible drug interactions may occur with:
Anacids (aluminum hydroxide type)
Antimuscarinics/anticholinergics
Diuretics and cardiovascular drugs
Neuromuscular blocking agents
Oral hypoglycemic agents
Encourage patients to take meds as prescribed.
These meds should never be stopped abruptly.
Report constipation or the development of any urinary hesitancy or bladder distension.
Teach pts to change positions slowly to prevent or minimize postural hypotension.
Avoid caffeine (excessive irritability)
Avoid alcohol ingestion and hazardous activities until blood levels become stable.
Pts should notify their physician if palpitations, dyspnea, nausea, or vomiting occur.
Monitor side effects.
Therapeutic effects: decreased angina, return to normal bp and pulse, etc.

ETC...
Beta blocker DO NOT vasodilate. They have no effect on Alpha. They decrease peripheral vascular resistance. Blocks responses of neurotransmitters on beta receptors.

What are the mechanisms of action for BP? A and b.
What are the mechanisms of action of beta blocker for treatment of afib? 2+3+4
“ .....” for CHF 1 + 5
Or heart attack “”.

The mechanism of action in a beta blocker in heart failure is which of the following?
(pay attention! May be more than one answer)

True or false....
Nonselective beta blockers should not be used in asthma pts. (true)
Alpha blockers should never be used in asthma pts. false

Beta blockers work on CHF bc the heart wants to beat faster bc it is “broke”. NE makes it beat faster, but we need rest to heal. Give a beta blocker to allow rest.