Pharmacology Chapter 18 - Adrenergic Agonists and Adrenergic Blockers
Finish the statement:
Because sympathetic and parasympathetic nervous systems produce an opposite response...
A drug that mimics the sympathetic and a drug that mimics the parasympathetic will have an __________ response (& vice versa)
Finish the statement:
Because sympathetic and parasympathetic nervous systems produce an opposite response...
A drug that mimics the sympathetic and blocks the parasympathetic will have a __________response (& vice versa)
The sympathetic nervous system is also known as?
What neurotransmitter is located at the adrenergic terminal nerve ending?
What is the parasympathetic nervous system known as?
What neurotransmitter is located at the cholinergic terminal nerve ending?
Drugs that stimulate the sympathetic nervous system because they mimic the neurotransmitters norepinephrine and epinephrine. They act on one or more of the adrenergic receptor sites located in the effector cells. There are 4 main receptors, alpha1, alpha2, beta1, beta2 (which mediate different responses)
INCREASES force of heart contraction;
vasoconstriction INCREASES BP;
mydriasis (dilation of pupil);
DECREASES secretion in salivary glands;
INCREASES urinary bladder relaxation and sphincter contraction
INHIBITS release of norepinephrine;
DILATES blood vessels;
DECREASES GI motility and tone
INCREASES heart rate AND force of contraction;
INCREASES renin secretion, which INCREASES BP
promotes GI and uterine RELAXATION;
promotes INCREASE in blood sugar thru glycogenolysis in liver;
INCREASES blood flow to skeletal muscles
The two enzymes that inactivate norepinephrine and where they are located?
MAO (monamine oxidase) inside the neuron
COMT (catechol-O-methyltransferase) outside the neuron
Drugs can prolong the action of the neurotransmitter (e.g. norepinephrine) by what 2 ways?
1- inhibit norepi reuptake, which prolongs the action
2- inhibit the degradation of norepi by enzyme action
The sympathomimetic drugs that stimulate adrenergic receptors are classified into 3 categories according to their effects on organ cells.
What are the 3 categories?
Direct Acting sympathomimetics, which directly stimulate the adrenergic receptor (e.g., norepi and epi)
Indirect Acting sympathomimetics, which stimulate the release of norepi from the terminal nerve endings (e.g., amphetamine)
Mixed Acting sympathomimetics (both direct and indirect acting), which stimulate the adrenergic receptor sites and stimulate the release of norepi from the terminal nerve endings (e.g., ephedrine)
Fig 18-3 p. 258
they are the chemical structures of a substance (either endogenous or synthetic) that can produce a sympathomimetic response.
Examples of endogenous catecholamines are:
Epinephrine, Norepinephrine, and dopamine
An endogenous catecholamine that acts on alpha1, alpha2, beta1, and beta2. In anaphylactic shock, it is useful because it increases blood pressure, heart rate, and airflow through the lungs. It is considered to be NONSELECTIVE because it affects different adrenergic receptors.
Pharmocokinetics & Pharmocodynamics
Administration: subQ, IV, topically, inhalation, intracardiac, and instillation methods. NOT GIVEN PO. High doses can cause dysrhythmias. It can also cause renal vasoconstriction, decreasing renal perfusion and urinary output.
Tricyclic antidepressants and MAOIs allow the effects to be intensified and prolonged. Administration with digoxin may caus dysrhythmias.
To treat anaphylaxis, asthma, bronchospasm, severe hypotension, cardiac arrest.
Acts on alpha and beta receptors;
promotes CNS & cardiac stimulation and bronchodilation
strengthens cardiac contraction
increases cardiac rate and output
reverses anaphylactic reactions
reduces mucosal congestion by inhibiting histamine release
Anorexia, nausea, vomiting, nervousness, tremors, agitation, sweating, headache, pallor, insomnia, weakness, and dizziness
(think of how a panic attack makes you feel)
palpitations, tachycardia, hypertension, dyspnea
Necrosis and gangrene of IV site upon infiltration
Life threatening: Ventricular fibrillation and pulmonary edema.
Info about IV administration
For cardiac resuscitation, 1 mg IV; may repeat q3-5 min. Follow each dose with 20 mL of saline flush to ensure proper delivery. It is normally administered 1 mg IV over 1 minute; however, in cardiac arrest, it may be given more rapidly. Monitor IV site frequently for because extravasation can cause tissue necrosis.
A beta2 adrenergic agonist that is selective for beta2 adrenergic receptors, so the response is relaxation of bronchial smooth muscle and bronchodilation.
If it is taken with and MAOI, hypertensive crisis can result. Beta blockers may inhibit the action of albuterol.
Check urinary output and bladder for distension because urinary retention can result from high drug dose. Offer food to patient to avoid nausea and vomiting. Evaluate blood glucose levels in diabetic patients because they may increase.
How to administer an epi pen
Do not use if solution is discolored or has particles in it. Inject subcutaneously. Apply sufficient pressure to activate epipen while holding device in place for 5-10 seconds. It should be inserted into outer thigh. Massage injection site for 10 seconds to promote absorption and reduce vasoconstriction and tissue irritation.
aka adrenergic antagonists or smpatholytics. They act as antagonists to adrenergic agonists by blocking the alpha and beta receptor sites.
Alpha Adrenergic Blockers aka Alpha Blockers
These drugs block or inhibit a response at the alpha adrenergic receptor site. They can cause orthostatic hypotension and reflex tachycardia, so they are not used as frequently as beta blockers.
They promote vasodialation, causing a decrease in BP. They can be used to treat peripheral vascular disease such as Raynaud's disease
Beta Adrenergic Blockers aka Beta Blockers
They can be selective or nonselective. Use extreme caution with nonselective beta blockers in patients with COPD or asthma.
They decrease the heart rate, and a decrease in BP usually follows. Useful in treating mild to moderate hypertension, angina pectoris, and myocardial infarction
THESE DRUGS COMMONLY END IN -LOL
The first beta blocker prescribed to treat angina, cardiac dysrhythmias, hypertension and heart failure. Also given for migranes. It has many side effects due to its nonselective response in blocking both beta1 & 2
A selective adrenergic blocker has a greater affinity for certain receptors. If the desired effect is to decrease pulse and BP, then a selective beta1 blocker such as ___ or ___ may be ordered.
metoprolol tartrate (Lopressor)
A selevtive beta1 blocker, and it is one of the most frequently prescribed drugs in the US. It decreases sympathetic outflow to the periphery and suppresses the renin angiotension aldosterone system response.
Contraindicated: bradycardia, heart block, cardiogenic shock, pulmonary edema, acute bronchospasm and pregnancy
drowsiness, dizziness, fainting, depression, alopecia, weakness, nausea, vomiting, diarrhea, cool extremities, impotence, decreased libido
bradycardia, hypotension, heart failure, masking of hypoglycemia
Life threatening: bronchospasm, pulmonary edema, dysrhythias, thrombocytopenia
Risk of hypoglycemia is increased when the pt is taking insulin and sulfonylureas.
NSAIDs decrease hypotensive effect.
chest pain related to decreased blood flow to heart
a condition in which you heart suddenly cant pump enough blood to meet your body's needs. most often caused by a severe heart attack
A patient with cardiac decompensation is receiving dobutamine as a continuous infusion. The patient’s blood pressure has increased from 100/80 mm Hg to 130/90 mm Hg. What is the nurse’s priority action?
- Assess hourly blood pressure readings.
- Assess the patient’s ECG and slow the infusion.
- Assess the patient’s respiratory rate and measure ABGs.
- Assess the patient’s I&O and decrease IV fluids.
The major therapeutic effect of dobutamine is to increase cardiac output. Cardiac output is reflected in the patient’s heart rate, blood pressure, and urine output. An increase in blood pressure is the expected therapeutic effect.
The nurse assesses a patient receiving an adrenergic (sympathomimetic) agent. Which finding will be of greatest concern to the nurse?
- Weak peripheral pulses and decreased heart rate
- Increased peripheral pulses and increased heart rate
- Stable blood pressure and increased cardiac output
- Heart rate of 95 beats per minute and strong peripheral pulses
Adrenergic agents stimulate the sympathetic nervous system, which increases heart rate (positive chronotropic effect), contractility (positive inotropic effect), and conductivity (positive dromotropic effect). The nurse would be most concerned that the pulses remain weak and heart rate decreased after receiving this drug, as the therapeutic effect is not being achieved.
The nurse assesses the peripheral intravenous infusion site of a patient receiving intravenous dopamine and suspects extravasation. What is the nurse’s primary action?
- Apply a cold pad to the site.
- Pull the IV immediately.
- Elevate the patient’s extremity.
- Stop the infusion.
The nurse’s first action is to stop the infusion, followed by infusing phentolamine (Regitine) into the area to counteract vasoconstrictive effects of the dopamine.
The nurse is caring for a patient diagnosed with heart failure and chronic obstructive pulmonary disease (COPD). The patient is ordered a nonselective beta blocker. What is the nurse’s primary intervention?
- Assess the heart rate before administration.
- Maintain the patient on intake and output.
- Make sure the patient is on telemetry monitoring.
- Call the health care provider to request a different medication.
Nonselective beta blockers are used to treat supraventricular dysrhythmias secondary to their negative chronotropic effects (decreasing heart rate). They may exacerbate heart failure and COPD. The patient could receive a selective beta blocker instead. The nurse should make the health care provider aware of the patient’s history of respiratory disease.
The nurse is caring for a patient who has been recently diagnosed with hypertension and is to receive an initial dose of atenolol (Tenormin). What is the nurse’s primary intervention?
- Assess the patient’s lungs.
- Teach the patient about beta blockers.
- Call the health care provider.
- Ask the patient if he has a history of any respiratory disease.
At therapeutic dosages, atenolol selectively blocks only the beta1 receptors in the heart, not the beta2 receptors located in the lungs. It is not necessary to determine specifically the history of respiratory disease. Although the nurse should assess the patient overall on a regular basis, the assessment should include all body systems, not only the lungs. It is not necessary to notify the health care provider prior to administration of the first dose of the medication.
A patient has been taking metoprolol (Lopressor) and tells the home care nurse, “I can’t afford this medication any more, and I stopped it yesterday.” What is the nurse’s priority action?
- Refer the patient to the social worker.
- Call the drug company to ask for assistance.
- Assess the patient’s blood pressure.
- Teach the patient that abrupt medication withdrawal may lead to a rebound hypertensive crisis.
Abrupt withdrawal of a beta blocker can cause rebound hypertension. The nurse should immediately check the patient’s blood pressure and then proceed with teaching and calling the health care provider.
The nurse is caring for a patient who is prescribed propranolol (Inderal). Which assessment finding will reveal if the medication is having a therapeutic effect?
- The patient’s lung sounds are clear.
- The patient is in sinus rhythm.
- The patient has strong peripheral pulses.
- The patient’s blood pressure is 130/75 mm Hg.
Propranolol (Inderal) is nonselective—it blocks both beta1 and beta2 receptors at therapeutic doses. The medication is administered to treat hypertension. The patient’s blood pressure is within normal limits, which indicates therapeutic effect.
Which is the highest priority potential nursing diagnosis for a patient who is starting on metoprolol (Lopressor)?
- Decreased cardiac output related to effects of medication
- Fatigue related to side effects of medication
- Knowledge deficit regarding pharmacologic therapy
- Risk for injury related to side effects of medication
Decreased cardiac output puts the patient at highest risk. Although the other nursing diagnoses are pertinent, they are not the priority.
The nurse is preparing to discharge a patient who is receiving acebutolol HCl (Sectral). Which instruction will the nurse include in the medication teaching plan for this patient?
- “If you take your pulse and it is less than 60, hold your medicine and call your health care provider for instructions.”
- “If you become dizzy, do not take your medication for 2 days and then restart on the third day.”
- “This medication may make you fatigued; increasing caffeine in your diet may help alleviate this problem.”
- “Increase intake of green leafy vegetables to prevent bleeding problems that can be caused by this medication.”
Acebutolol HCl (Sectral), a beta blocker, has negative chronotropic effects and could cause symptomatic bradycardia and/or heart block. The health care provider should be consulted before acebutolol is administered to a patient with bradycardia (heart rate less than 60 beats/min).
A nurse is preparing to administer a beta blocker to a patient. The nurse recognizes that beta blockers are used to treat which conditions? (Select all that apply.)
- Angina pectoris
- Cardiogenic shock
- Chronic obstructive pulmonary disease (COPD)
- Congestive heart failure (CHF)
- Sinus bradycardia
Beta blockers are effective in treating hypertension (secondary to negative inotropic effects) and angina pectoris (decreases cardiac workload when decreasing heart rate and contractility). Beta blockade has also been shown to reduce mortality in patients with CHF.