Nursing Pharmacology Chapter 5:
Table of Contents
Positive inotropic agent
of bronchospasm impatient with asthma
Addition to local
anesthetic solutions -- reducing systemic local
of severe allergic (hypersensitivity) reactions
Hypovolemic shock: Dehydration or
Cardiac Failure (Cardiogenic Shock
(pump failure) due to excessive myocardial tissue
loss or arrhythmia
Cardiac Output obstruction
(pulmonary embolism, aortic dissection,
Loss of peripheral vascular tone
(Septic Shock or anaphylaxis)
Used in Treating Shock
α agonists: increase peripheral vascular resistance
mephenteramine and methoxamine may be
used to maintain blood pressure in severe hypotension.
The objective is to ensure
adequate CNS perfusion.
The use of these agents
may be indicated if the hypotensive state
is due to sympathetic failure, such as
possibly occurring following spinal
anesthesia or injury.
In shock due to
other causes, reflex vasoconstriction is
typically intense; adding a agonists may be
harmful by further compromising organ
(e.g. renal) perfusion.
ß- agonists: increase heart rate and
Increasing heart rate and contractility
by isoproterenol, epinephrine or
norepinephrine may adversely affect
cardiac performance in damaged
agents increase myocardial oxygen
requirements and may induce arrhythmias.
by increasing afterload (α receptor activation)
may worsen myocardial performance
Dopamine and Dobutamine
(Intropin), at low
concentrations, acts at D1 receptors and
improve myocardial contractility
Dopamine (Intropin) produces
less of an increase in heart rate
compared to isoproterenol and dopamine
dilates renal arteries, promoting better
(Dobutrex), through complex actions
mediated by a
and ß receptors enhances
contractility without substantially
increasing either heart rate or
in Cardiogenic Shock:
Nitrates, Adrenergic Agonists, Amrinone (Inocor) and Milrinone (Primacor)
In cardiogenic shock
precipitated by acute myocardial
infarction, salvage of reversibly damaged
myocardial may be accomplished by:
i.v. nitroglycerin (decreasing preload)
balloon pump (reducing afterload)
surgery to repair
valve pathologies or to
may be caused myocardial stunning due to
prolonged cardiopulmonary bypass.
Dopamine (Intropin) and Dobutamine
(Dobutrex) may be useful as
positive inotropic agents
Amrinone (Inocor) and milrinone (Primacor)
have positive inotropic effects
that may be useful if other
agents are ineffective.
Centrally-acting sympathomimetics, such as clonidine (Catapres) or
methyldopa (Aldomet), are effective
For clonidine (Catapres), the
mechanism of action is activation of α2 adrenergic receptors which
then reduce sympathetic outflow.
arrest, epinephrine may be beneficial.
During external cardiac massage a agonists may improve cerebral perfusion
by shunting blood to the brain (since cerebral
vessels are thought to be relatively insensitive
to vasoconstricting effects of these drugs).
Epinephrine by activating both a and ß adrenergic receptors increase
diastolic pressures improving coronary perfusion.
Termination of paroxysmal
supraventricular tachycardia may be accomplished
by increased vagal (cholinergic) reflex tone
administration. Other drugs (e.g. adenosine, Ca2+
channel blockers) are more commonly used.
Congestive Heart Failure
ß adrenergic receptor agonists
have had limited use in chronic management of
congestive heart failure.
In congestive failure, a
significant loss of ß1 receptors
(50%) occurs. Loss of receptor number and
desensitization limit ß adrenergic receptor
Effects: α-Adrenergic Agonists
Vasoconstriction-reduced bleeding in surgical
procedures nose and throat surgical procedures.
agonists may be injected into the penis for
treatment of priapism.
Sinus surgery: local
application of phenylephrine or oxymetazoline for
agonists are effective decongestants. (allergic,
acute or chronic rhinitis).
These agents increase
airflow by decreasing nasal mucosal volume.
Nasal mucosal volume is decreased
by α1 adrenergic receptor constricting
effects on nasal venous capacitance vessels.
Chronic use or upon
discontinuation, a "rebound" hyperemia
worsens congestion. This rebound effect and loss
of efficacy with chronic use limits clinical
alpha-adrenergic agonists, such as
phenylephrine, should be used with caution in
hypertensive patients or those using a monoamine
oxidase inhibitor (MAO).
Preparations are available for
both oral and topical use. Oral use is associated
with increased systemic effects.
adrenergic receptor agonists have a prominent
role in chronic and acute management of asthma.
selective adrenergic receptor agonists, mediating
bronchodilation, are preferable.
Clinical management of asthma is
discussed in more detail elsewhere.
Epinephrine is the agent of choice
in emergency management of acute hypersensitivity
reactions (reaction to food, insect bites, drug
administration alleviate symptoms rapidly and may
be lifesaving when airway is compromised or in
Mechanism: ß adrenergic receptor
activation may suppress mast release of histamine
and leukotriene mediators.
Glucocorticoids and antihistamines
are also used in management of severe
- Hollenberg, S.M. and Parrillo,
J.E., Shock, In Harrison's Principles of Internal
Medicine 14th edition, (Isselbacher, K.J., Braunwald, E.,
Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L.,
eds) McGraw-Hill, Inc (Health Professions Division),
1998, p. 215-222
- Hoffman, B.B and Lefkowitz, R.J,
Catecholamines, Sympathomimetic Drugs, and Adrenergic
Receptor Antagonists, In, Goodman and Gillman's The
Pharmacologial Basis of Therapeutics,(Hardman, J.G,
Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman,
A.G.,eds) TheMcGraw-Hill Companies, Inc.,1996,
- Stoelting, R.K.,
"Sympathomimetics", in Pharmacology and
Physiology in Anesthetic Practice, Lippincott-Raven
Publishers, 1999, p.259.