MSU-IIT
College of Nursing
NSG105: Pharmacology
Lorie Ann S. Balili, MAN, CNN, RN
AUTONOMIC NERVOUS SYSTEM AGENTS
Central Nervous System (CNS)
® Body’s primary nervous system, consisting of
the brain and spinal cord.
® Interpretation
Peripheral Nervous System (PNS)
® located outside the brain and spinal cord,
® Made up of two divisions: the autonomic and
the somatic.
® Receives stimuli & initiates responses to these
stimuli
2.
Parasympathetic nerves
— Also called the cholinergic system
— Neurotransmitter: Acetylcholine
§
Innervates the muscle
§
Stimulates the receptor cells
to produce a response, but
the enzyme
acetylcholinesterase may
inactivate acetylcholine
before it reaches the
receptor cell.
— Cholinergic receptors (either
nicotinic or muscarinic) meaning
they are stimulated by the
alkaloids nicotine & muscarine
Somatic Nervous System
® Voluntary system that innervates skeletal
muscles over which there is control.
Sympathetic and Parasympathetic Responses
to Drugs
Autonomic Nervous System
® also called the visceral system
® Acts on smooth muscles and glands
® Functions: (control and regulation)
1. Heart
2. Respiratory system
3. Gastrointestinal tract
4. Bladder
5. Eyes
6. Glands
® An involuntary nervous system over which we
have little or no control.
® The two sets of neurons in the autonomic
component of the PNS are the:
1. Afferent neurons - send impulses to
the CNS, where they are interpreted
2. Efferent neurons - Receive the
impulses (information) from the brain
and transmit these impulses through
the spinal cord to the effector organ
cells.
® The efferent pathways in the ANS are divided
into two branches:
1. Sympathetic nerves
— Also called the adrenergic system
— (adrenaline)
— Neurotransmitter: norepinephrine
§
Released from the terminal
nerve ending and stimulates
the cell receptors to
produce a response.
— Adrenergic receptor organ cells
are of four types: alpha1, alpha2,
beta1, and beta2
SANCO, RC
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MSU-IIT
College of Nursing
1.
2.
3.
4.
NSG105: Pharmacology
Lorie Ann S. Balili, MAN, CNN, RN
OUTLINE
Adrenergic Agonists
•
Inactivation of Neurotransmitters
•
Classification of Sympathomimetics
•
Epinephrine
•
Albuterol
Central – Acting Alpha Agonists
•
Clonidine and Methyldopa
•
Nursing Process: Patient-Centered
Collaborative Care:
Adrenergic Agonist
Adrenergic Blockers (Antagonists)
•
Alpha-Adrenergic Blockers
•
Beta-Adrenergic Blockers
•
Adrenergic Neuron Blockers
•
Nursing Process: Patient-Centered
Collaborative Care:
•
Adrenergic Neuron Blockers
NCLEX Study Questions
ADRENERGIC AGONISTS
® Sympathomimetics
® Drugs that stimulate the sympathetic
nervous system are called adrenergics,
adrenergic agonists or sympathomimetics
because they mimic the sympathetic
neurotransmitters norepinephrine and
epinephrine.
® Act on one or more adrenergic receptor
sites located in the effector cells of the
muscles, such as the (1) heart,
(2) bronchiole walls, (3) gastrointestinal
(GI) tract (4) urinary bladder, and (5)
ciliary muscle of the eye.
® The four main receptors are alpha1,
alpha2, beta1, and beta2, which mediate
the major responses.
® The alpha-adrenergic receptors are
located in blood vessels, eye, bladder,
and prostate.
Alpha1 receptors
® When the alpha1 receptors in vascular
tissues (vessels) of muscles are
stimulated:
• arterioles and venules constrict
• increasing peripheral resistance
• blood return to the heart
® Circulation is improved, and blood
pressure is increased. When there is too
much stimulation, blood flow is
decreased to the vital organs
Alpha2 receptors
® Located in the postganglionic
sympathetic nerve endings.
® When stimulated:
• It inhibits the release of
norepinephrine
• leading to a decrease in
vasoconstriction.
® This results in vasodilation and a
decrease in blood pressure.
Beta1 receptors
® Located in the kidney but primarily in
the heart.
® When stimulated:
• Increases myocardial contractility
and heart rate
Beta2 receptors
® found mostly in the smooth muscles of
the lung and gastrointestinal tract,
liver, and uterine muscle.
® Stimulation of the beta2 receptor
causes:
• Relaxation of the smooth muscles
of the lungs, resulting in
bronchodilation
• Decrease in gastrointestinal tone
and motility
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College of Nursing
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®
®
®
®
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NSG105: Pharmacology
Lorie Ann S. Balili, MAN, CNN, RN
Activation of glycogenolysis in the
liver and increased blood glucose
• Relaxation of the uterine
muscle, resulting in a decrease in
uterine contraction
Dopaminergic
Located in the renal, mesenteric,
coronary, and cerebral arteries.
When this receptor is stimulated:
• Vessels dilate
• Blood flow increases
Only dopamine can activate this
receptor.
Inactivation of Neurotransmitters
After the neurotransmitter (e.g.,
norepinephrine) has performed its
function, the action must be stopped to
prevent prolonging the effect.
Transmitters are inactivated by:
(1) Reuptake of the transmitter back
into the neuron (nerve cell
terminal)
(2) Enzymatic transformation or
degradation
(3) Diffusion away from the receptor
The mechanism of norepinephrine
reuptake plays a more important role
in inactivation than the enzymatic
action. Following the reuptake of the
transmitter in the neuron, the
transmitter may be degraded or
reused.
® The two enzymes that inactivate
norepinephrine:
(1) monoamine oxidase (MAO) - is
inside the neuron
(2) catechol-O-methyltransferase
(COMT) - outside of the neuron.
® Drugs can prolong the action of the
neurotransmitter (e.g., norepinephrine)
by either
(1) inhibiting the norepinephrine
reuptake, which prolongs the
action of the transmitter
(2) inhibiting the degradation of
norepinephrine by enzyme
action.
Classification of Sympathomimetics
® The sympathomimetic drugs that
stimulate adrenergic receptors are
classified into three categories
according to their effects on organ
cells.
® Categories include:
1. direct-acting sympathomimetics
— directly stimulate the
adrenergic receptor (e.g.,
epinephrine or
norepinephrine)
2. indirect-acting
sympathomimetics,
— stimulate the release of
norepinephrine from the
terminal nerve endings (e.g.,
amphetamine)
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MSU-IIT
College of Nursing
3.
NSG105: Pharmacology
Lorie Ann S. Balili, MAN, CNN, RN
mixed-acting sympathomimetics
— (both direct and indirect
acting)
— stimulate the adrenergic
receptor sites and stimulate
the release of norepinephrine
from the terminal nerve
endings (e.g., ephedrine)
— Pseudoephedrine is an
example of a mixed-acting
sympathomimetic.
o This drug acts indirectly
by stimulating the
release of norepinephrine
from the nerve terminals
and acts directly on the
alpha1 and beta1
receptors.
o Like epinephrine, it
increases heart rate.
o It is not as potent a
vasoconstrictor as
epinephrine, and there is
less risk of hemorrhagic
stroke and hypertensive
crisis.
o Helpful to relieve nasal
and sinus congestion
without rebound
congestion.
• Catecholamines
® chemical structures of a substance
(either endogenous or synthetic) that
can produce a sympathomimetic
response.
® Examples of endogenous
catecholamines are: epinephrine,
norepinephrine, and dopamine.
® Synthetic catecholamines are
isoproterenol and dobutamine.
Noncatecholamines
® (e.g., phenylephrine, metaproterenol,
albuterol) stimulate the adrenergic
receptors.
® Most noncatecholamines have a longer
duration of action than the
endogenous or synthetic
catecholamines.
Epinephrine
® acts on alpha1-, alpha 2-, beta1-, and
beta2- adrenergic receptor sites.
® The responses from these receptor
sites include:
(1) increase in blood pressure
(2) pupil dilation
(3) increase in heart rate
(tachycardia)
(4) bronchodilation
® In anaphylactic shock, it increases
blood pressure, heart rate and airflow
through the lungs.
® Because it affects different adrenergic
receptors, it is nonselective.
Pharmacokinetics:
• Administered subcutaneously,
intravenously, topically, or by
inhalation, intracardiac, and instillation
methods.
— It is not given orally, because it
is rapidly metabolized in the GI
tract and liver resulting in
unstable serum levels.
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MSU-IIT
College of Nursing
NSG105: Pharmacology
Lorie Ann S. Balili, MAN, CNN, RN
Pharmacodynamics:
• Epinephrine is frequently used in
emergencies to treat anaphylaxis,
which is a life-threatening allergic
response.
• Epinephrine is a potent inotropic
(strengthens myocardial contraction)
drug that
(1) increases cardiac output
(2) promotes vasoconstriction and
systolic
blood
pressure
elevation
(3) increases heart rate
(4) produces bronchodilation.
• High doses can result in cardiac
dysrhythmias necessitating
electrocardiogram (ECG) monitoring.
• Epinephrine can also cause renal
vasoconstriction, thereby decreasing
renal perfusion and urinary output
Albuterol
® Albuterol sulfate (Proventil), a beta2adrenergic agonist, is selective for
beta2-adrenergic receptors
® Response: relaxation of bronchial
smooth muscle and bronchodilation.
® A patient with asthma may tolerate
albuterol better than isoproterenol
(which activates beta1 and beta2
receptors) because albuterol’s action is
more selective (activates only the beta2
receptors).
o By using selective sympathomimetics,
fewer undesired adverse effects will
occur. However, high dosages of
albuterol may affect beta1 receptors,
causing an increase in heart rate.
Pharmacokinetics:
® Absorbed from the GI tract and
extensively metabolized by the liver.
® The half-life of the drug differs:
(oral route is 2.7 to 6 hours; inhalation
route is 3.5 hours).
Pharmacodynamics
® The primary use of albuterol is to
prevent and treat bronchospasm.
® With inhalation, the onset of action of
albuterol is faster than with oral
administration, though the duration of
action is the same for both oral and
inhalation preparations.
® Side effects: Tremors, restlessness, and
nervousness
® If albuterol is taken with an MAOI,
hypertensive crisis can result.
CENTRAL-ACTING ALPHA AGONISTS
Clonidine (Catapres)
® A selective alpha2-adrenergic agonist
(sympathomimetic) used primarily to
treat hypertension.
® Alpha2 drugs act by decreasing the
release of norepinephrine from
sympathetic nerves and decreasing
peripheral adrenergic receptor
activation.
— produce vasodilation by
stimulating alpha2 receptors in
the central nervous system
(CNS), leading to a decrease in
blood pressure
Methyldopa (Aldomet)
® An alpha-adrenergic agonist
(sympathomimetic) that acts within
the CNS.
® This drug is taken up into the
brainstem neurons and converted to
methylnorepinephrine, which is an
alpha2-adrenergic agonist that leads to
alpha2 activation.
® The decrease of sympathetic outflow
from the CNS causes vasodilation and
a reduction in blood pressure
Side Effects and Adverse Reactions
® Undesired side effects frequently result
when the drug dosage is increased or
the drug is nonselective.
® Side effects commonly associated with
adrenergic agonists include:
(1) Hypertension
(2) Tachycardia
(3) Palpitations
(4) Restlessness
(5) Tremors
(6) Dysrhythmias
(7) Dizziness
(8) Urinary retention
(9) Nausea
(10) Vomiting
(11) Dyspnea
(12) Pulmonary edema
Note: Look Table 18-2: Adrenergic Agonists
(Alpha1, Beta1 and Beta2) page 279 (book)
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MSU-IIT
College of Nursing
NSG105: Pharmacology
Lorie Ann S. Balili, MAN, CNN, RN
ADRENERGIC BLOCKERS (ANTAGONISTS)
® Drugs that block the effects of
adrenergic neurotransmitters
® Called adrenergic blockers, adrenergic
antagonists, or sympatholytics.
® They act as antagonists to adrenergic
agonists by blocking the alpha and beta
receptor sites.
® They block the effects of the
neurotransmitter either directly by
occupying the receptors or indirectly by
inhibiting
the
release
of
the
neurotransmitters norepinephrine and
epinephrine.
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MSU-IIT
College of Nursing
NSG105: Pharmacology
Lorie Ann S. Balili, MAN, CNN, RN
Alpha-Adrenergic Blockers
® Drugs that block or inhibit a response
at the alpha-adrenergic receptor site
® Alpha-blocking agents are divided into
two groups:
(1) Selective alpha blockers block alpha1
(2) Nonselective alpha blockers block alpha1 and alpha2.
® Because alpha- adrenergic blockers
can cause orthostatic hypotension and
reflex tachycardia, many of these
drugs are not as frequently prescribed
as beta blockers.
® Alpha blockers promote vasodilation,
causing a decrease in blood pressure.
— If vasodilation is long-standing,
orthostatic hypotension can
result.
— Dizziness may also be a
symptom of a drop in blood
pressure.
(As, BP decrease, PR increases
to compensate for the low BP
and inadequate blood flow)
® Alpha blockers can be used to treat
peripheral vascular disease (e.g.,
Raynaud’s disease).
— Vasodilation occurs,
permitting more blood flow to
the extremities.
® These drugs are also helpful in
decreasing symptoms of benign
prostatic hypertrophy.
Beta-Adrenergic Blockers
® Commonly called Beta blockers
® Functions:
(1) Decrease heart rate
(2) Decrease in blood pressure
(3) Bronchoconstriction
® Beta blockers are useful in treating:
(1) Mild to moderate hypertension
(2) Angina Pectoris
(3) Myocardial Infarction
® Nonselective-beta blockers
— (block both beta1 and beta2)
should be used with extreme
caution in pt who has Chronic
obstructive pulmonary disease
(COPD) or Asthma
Propranolol hydrochloride (Inderal)
- The first beta blocker prescribed to
treat angina, cardiac
dysrhythmias, hypertension, and
heart failure.
- This medication is given for
migraine prophylaxis.
- Although it is still prescribed today,
propranolol has many side effects,
partly because of its nonselective
response in blocking both beta1 and
beta2 receptors.
® Selective adrenergic blocker
— Has a greater affinity for
certain receptors.
— If the desired effect is to
decrease PR and BP, then a
selective beta1 blocker such as
Atenolol (Tenormin) or
metoprolol tartrate
(Lopressor) may be ordered.
® Intrinsic sympathomimetic activity
(ISA) - the ability of certain beta
blockers to bind with a beta receptor
to prevent strong agonists from
binding to that receptor producing
complete activation.
o Nonselective beta blockers (block both
beta1 and beta2) that have ISA include:
(1) Carteolol
(2) Carvedilol,
(3) Penbutolol
(4) Pindolol.
o Selective blocker (blocks beta1 only)
that has ISA is acebutolol.
These agents may be recommended
for patients experiencing bradycardia.
Atenolol (Tenormin)
® a selective beta1 blocker, frequent
prescribed drug in US
® Functions:
(1) decreases sympathetic outflow
to the periphery
(2) suppresses the reninangiotensin-aldosterone
system response
® Contraindications:
(1) Bradycardia
(2) Heart block
(3) Cardiogenic shock
(4) Pulmonary edema
(5) Acute bronchospasm
(6) Pregnancy
§ Pharmacokinetics
— Atenolol is 50% absorbed from
the GI tract. It does not readily
cross the blood-brain barrier.
— It has a half-life of 3 to 6 hours
and is eliminated in urine and
feces.
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MSU-IIT
College of Nursing
§
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NSG105: Pharmacology
Lorie Ann S. Balili, MAN, CNN, RN
Pharmacodynamics
- By blocking beta1 receptors,
atenolol decreases:
(1) Heart rate
(2) Peripheral vascular resistance
(3) Force of cardiac contractions
(4) Cardiac output
(5) Systolic and Diastolic blood
pressure.
Drug Interactions
- Many drugs interact with atenolol.
- Nonsteroidal anti-inflammatory
drugs (NSAIDs) decrease the
hypotensive effect of atenolol.
- Hypotension can be potentiated if
atenolol is taken with another
antihypertensive.
- When atenolol is given
concurrently with atropine and
other anticholinergics, absorption
is increased.
Side Effects and Adverse Reactions
® The side effects commonly associated
with beta blockers are:
(1) Bradycardia
(2) Hypotension
(3) Headache
(4) Dizziness
(5) cold extremities
(6) hypoglycemia
(7) bronchospasm.
® General side effects of beta-adrenergic
blockers include:
(1) cardiac dysrhythmias
(2) flushing
(3) hypotension
(4) weakness
(5) impotence
(6) decreased libido
(7) depression
(8) pulmonary edema.
® Usually the side effects are dose related.
Adrenergic Neuron Blockers
® Drugs that block the release of
norepinephrine from the sympathetic
terminal neurons
® Function: Decrease blood pressure
Reserpine
® an adrenergic neuron blocker,
antihypertensive agent.
® Effects of this drug closely resemble
those of alpha- and beta-adrenergic
blockers.
® Reduces the serotonin and
catecholamine transmitters
o Depletion of these neurotransmitters
may lead to severe mental depression.
Note: Look Table 18-4: Adrenergic Blockers
page 282-283 (book)
NCLEX STUDY QUESTIONS
1.
2.
3.
§
4.
5.
6.
7.
The nurse will monitor the patient taking
albuterol (Proventil) for which conditions?
(Select all that apply.)
a. Palpitations
b. Hypertension
c. Hypoglycemia
d. Bronchospasm
e. Uterine contractions
Nadolol (Corgard) is prescribed for a patient.
The nurse realizes that this drug is a betaadrenergic blocker and that this drug
classification is contraindicated for patients with
which condition?
a. Hypothyroidism
b. Angina pectoris
c. Bronchial asthma
d. Liver dysfunction
The nurse realizes that beta1 receptor
stimulation is differentiated from beta2
stimulation in that stimulation of beta1 receptors
leads to which condition?
a. Increased bronchodilation
b. Decreased uterine contractility
c. Increased myocardial contractility
d. Decreased blood flow to skeletal muscles
A patient is given epinephrine (Adrenalin), an
adrenergic agonist (sympathomimetic). The
nurse should monitor the patient for which
condition?
a. Decreased pulse
b. Pupil constriction
c. Bronchial constriction
d. Increased blood pressure
A patient who is taking epinephrine is also
taking several other medications. The nurse
should realize that there is a possible drug
interaction with which drugs? (Select all that
apply.)
a. albuterol (Proventil)
b. metoprolol (Lopressor)
c. propranolol (Inderal)
d. digoxin (Lanoxin)
e. methyldopa (Aldomet)
A patient is prescribed metoprolol (Lopressor)
to treat hypertension. It is important for the
nurse to monitor the patient for which
condition? (Select all that apply.)
a. Bradycardia
b. Hypotension
c. Ankle edema
d. Decreased respirations
e. Increased respirations
The nurse is administering atenolol (Tenormin)
to a patient. Which concurrent drugs does the
nurse expect to most likely cause an
interaction? (Select all that apply.)
a. ginseng supplement
b. An NSAID, such as aspirin
c. atropine, an anticholinergic
d. haloperidol (Haldol)
e. methyldopa (Aldomet)
SANCO, RC
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MSU-IIT
College of Nursing
NSG105: Pharmacology
Lorie Ann S. Balili, MAN, CNN, RN
CHOLINERGIC AGONISTS AND ANTICHOLINERGICS
OUTLINE
1.
2.
3.
§
Cholinergic Agonists
• Direct-Acting Cholinergic Agonists
• Indirect-Acting Cholinergic Agonists
Anticholinergics
• Atropine
NCLEX Study Questions
CHOLINERGIC AGONISTS
® Drugs that stimulate parasympathetic
nervous system
® Called cholinergic agonists,
parasympathomimetics, cholinomimetics
or cholinergic stimulants
® Mimic the neurotransmitter acetylcholine
® Two types of cholinergic receptors:
1. Muscarinic receptor – stimulate
smooth muscle and slow heart rate
2. Nicotinic receptors – neuromuscular;
affect skeletal muscles
o Many
cholinergic
agonists
are
nonselective because they can affect
both the muscarinic and nicotinic
receptors. However, there are selective
cholinergic agonists for the muscarinic
receptors that do not affect the nicotinic
receptors.
Effects of Parasympathetic or
Cholinergic Stimulation
1. EYES - Pupils to constrict
2. LUNGS - Constrict bronchioles and
increase secretions
3. HEART - Heart rate to decrease
4. BLOOD VESSELS – dilate
5. GASTROINTESTINAL – Increase
peristalsis and secretions
6. BLADDER – Contracts
7. SALIVARY GLAND - Increase salivation
Direct- Acting Cholinergic Agonists
® Act on receptors to activate a tissue
receptor
® Selective to muscarinic receptors but are
nonspecific because the muscarinic
receptors are located in the smooth muscle
of the GI, genitourinary tracts, glands and
heart.
§
§
DRUGS
Bethanechol chloride (Urecholine)
® a direct-acting cholinergic agonist, acts
on the muscarinic (cholinergic)
receptor
® Function: Used primarily to increase
micturition (urination) in the treatment
of urinary retention and neurogenic
bladder.
Pharmacokinetics:
— Poorly absorbed from the GI Tract
— PB & HL: unknown
— Excreted in urine
Pharmacodynamics:
— Promote micturition by stimulating
the muscarinic cholinergic
receptors in the detrusor muscle to
contract the bladder and produce
urine output.
— Pt voids approx. 30 minutes to 1.5
hours after taking oral dose
— Increases peristalsis in the GI tract
— Should be taken on an empty
stomach
— Should not be administered by
injection
Metoclopramide HCl (Reglan)
® direct-acting cholinergic agonist that
is usually prescribed to treat
gastroesophageal reflux disease
(GERD).
® Function: Accelerates gastric emptying
time.
Pilocarpine
® Function: Constricts the pupils of the
eyes, thus opening the canal of
Schlemm to promote drainage of
aqueous humor (fluid).
® Treat: Glaucoma by relieving fluid
(intraocular) pressure in the eye and to
promote miosis in eye surgery and
examinations.
® Oral form: Relieve xerostomia (dry
mouth)
Side effects and Adverse Reactions
® Mild to severe side effects of most
muscarinic agonists such as
bethanechol include:
(1) Hypotension
(2) Bradycardia
(3) Blurred vision
(4) Excessive salivation
(5) Increased gastric acid secretion
(6) Abdominal cramps
(7) Diarrhea
(8) Bronchoconstriction
(9) Cardiac dysrhythmias
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MSU-IIT
College of Nursing
NSG105: Pharmacology
Lorie Ann S. Balili, MAN, CNN, RN
® Note: Prescribed cautiously for pt’s
with low blood pressure and heart
rates.
® Contraindication: Pt’s with (1) intestinal
or urinary tract obstruction, (2) severe
bradycardia and (3) active asthma.
Indirect- Acting Cholinergic Agonists
® Do not act on receptors
® Inhibit the action of the enzyme
cholinesterase (ChE) (acetylcholinesterase)
by forming a chemical complex, thus
permitting acetylcholine to accumulate at
the receptor sites
® Drugs that inhibit cholinesterase are called
cholinesterase inhibitors,
acetylcholinesterase (AChE) inhibitors, or
anticholinesterases
® Cholinesterase may destroy acetylcholine
before it reaches the receptor or after it has
attached to the site.
o By inhibiting or destroying the enzyme
cholinesterase, more acetylcholine is
available to stimulate the receptor and
remain in contact with it longer.
Function
of enzyme cholinesterase
®
• Breakdown into choline and acetic acid
• Small amount of cholinesterase can
break down a large amount of
acetylcholine in a short period.
• A cholinesterase inhibitor drug binds
with cholinesterase, allowing
acetylcholine to activate the
muscarinic and nicotinic cholinergic
receptors.
Inhibitors
® Cholinesterase inhibitors can be separated
into two: (effects vary with how long the
cholinesterase is bound)
1. Reversible Inhibitors
— Bind the enzyme cholinesterase for
several minutes to hours
— Function
(1) To produce pupillary
constriction in the treatment of
glaucoma
2.
(2) To increase muscle strength in
patients with myasthenia
gravis.
— Drugs used to increase muscular
strength in myasthenia gravis
(1) Neostigmine (Prostigmin)
(2) Pyridostigmine bromide
(Mestinon)
(3) Ambenonium chloride
(Mytelase [long-acting])
(4) Edrophonium chloride
(Tensilon [short-acting for
diagnostic purposes])
— Reversible Anticholinesterase drug:
(1) Opthalmic Form (Isopto
Eserine)
(2) Physotigmine (Antilirium)
– used as antidote for
atropine to reverse
anticholinergic toxicity
— Side effects
• For reversible
cholinesterase drug; it is
required for pt.’s who have
the following:
(1) Bradycardia
(2) Asthma
(3) Peptic ulcers
(4) Hyperthyroidism
• Cholinesterase inhibitors
are contraindicated for
pt’s with intestinal or
urinary obstruction.
Irreversible Inhibitors
— Bind the enzyme permanently
— Potent agents because of longlasting effect
— Enzyme cholinesterase must be
regenerated before the drug effect
diminishes—a process that may
take days or weeks.
— Function: Used to produce
pupillary constriction.
SANCO, RC
10
MSU-IIT
College of Nursing
NSG105: Pharmacology
Lorie Ann S. Balili, MAN, CNN, RN
ANTICHOLINERGICS
Drugs that inhibit the actions of acetylcholine
by occupying the acetylcholine receptors
® Called anticholinergics or
parasympatholytics.
® Other names used for anticholinergics:
a) cholinergic blocking agents
b) cholinergic or muscarinic
antagonists
c) antiparasympathetic agents
d) antimuscarinic agents
e) antispasmodics
® Major body tissues and organs affected by
the anticholinergic group of drugs are:
a) Heart
b) Respiratory tract
c) GI tract
d) Urinary bladder
e) Eyes
f) Exocrine glands
® By blocking the parasympathetic nerves,
the sympathetic (adrenergic) nervous
system dominates.
® Major responses to anticholinergics:
a) Decrease GI motility
b) Decrease in salivation
c) Dilation of pupils (mydriasis)
d) Increase pulse rate
Other
Effects: Decreased bladder
®
contraction
Result:
a) Urinary retention
b) Decreased rigidity and tremors r/t
neuromuscular excitement
® An anticholinergic can act as an antidote
to the toxicity caused by cholinesterase
inhibitors and organophosphate ingestion.
Atropine
® First derived from the belladonna plant
(Atropa belladonna) and purified in 1831, is
a classic anticholinergic, or muscarinic
antagonist drug.
® Atropine and scopolamine act on
muscarinic receptors, but they have little
effect on nicotinic receptors.
® Function:
(1) Preoperative medication to
decrease salivary secretions
(2) Agent to increase heart rate when
bradycardia is present.
® Atropine or auto-injector (Atropen) can
also be used as an antidote for muscarinic
agonist poisoning caused by an overdose of
a cholinesterase inhibitor or a muscarinic
drug such as bethanechol.
® Synthetic anticholinergic drugs – used as
antispasmodics to treat peptic ulcers and
intestinal spasticity
Ex: Propantheline bromide (Pro-Banthine) –
decreases gastric secretions and GI spasms
Pharmacokinetics
® Absorption: Orally and Parenterally
® Distribution: It crosses the blood-brain
barrier and exerts its effect on the central
nervous system (CNS). The protein binding
is unknown. It crosses the placenta.
® Metabolism: Short half-life, little cumulative
effect
® Excretion: Urine (75% to 95%)
SANCO, RC
11
MSU-IIT
College of Nursing
NSG105: Pharmacology
Lorie Ann S. Balili, MAN, CNN, RN
Pharmacodynamics
® Atropine sulfate blocks acetylcholine by
occupying the muscarinic receptor.
® It increases the heart rate by blocking
vagus stimulation and promotes dilation of
the pupils by paralyzing the iris sphincter.
® Other function:
(1) Used ophthalmically for mydriasis
and cycloplegia before eye exams
(2) Treat inflammation of the iris (iritis)
and uveal tract.
® Onset of action orally: Bet. 0.5 to 1 hour,
Peak at 1 hour
® For IM route, onset of action: 10-30 minutes,
peak at 30 minutes
® Duration for oral and IM route: 4 hours; via
IV routes
Onset of action: Immediate,
Peak action: 2 to 4 minutes
Side Effects and Adverse Reactions
® Common side effects of atropine and
atropine-like drugs include:
(1) Dry mouth
(2) Decreased perspiration
(3) Blurred vision
(4) Tachycardia
(5) Constipation
(6) Urinary retention
® Other side effects and adverse reactions
are:
(1) Nausea
(2) Headache
(3) Dry skin
(4) Abdominal distention
(5) Hypotension or hypertension
(6) Impotence,
(7) Photophobia (intolerance of bright
light)
(8) Coma
Antiparkinson- Anticholinergic Drugs
® Additional
studies
indicate
that
anticholinergic (antimuscarinic) agents
affect the CNS as well as the
parasympathetic nervous system.
® These anticholinergic drugs affect the CNS
by suppressing the tremors and muscular
rigidity of parkinsonism, but they have little
effect on mobility and muscle weakness
® Several anticholinergic drugs were
developed for the treatment of Parkinson’s
disease:
(1) Trihexyphenidyl hydrochloride
[Artane]
(2) Biperiden [Akineton]
(3) Benztropine [Cogentin]
—
—
May be used in combination with
levodopa/carbidopa to control
parkinsonism or used alone to treat
pseudoparkinsonism, which results
from the side effects of the
phenothiazines in antipsychotic drugs
Benztropine
§ Pharmacokinetics
® Absorption: Well-absorbed from the
GI tract
® Metabolism: PB: Unknown
® Distribution: HL: Unknown
® Excretion: Urine
§
Pharmacodynamics
® Function
(1) Decreases involuntary movement
(2) Diminishes the signs and
symptoms of tremors and muscle
rigidity that occur with
Parkinson’s disease and
pseudoparkinsonism.
® Availability: Oral tablet and Parenteral
(IM & IV injections)
® Alcohol and other CNS depressants
potentiate sedation.
® Anticholinergics, phenothiazines, and
tricyclic antidepressants may increase
the anticholinergic effects of
benztropine.
® The side effects are similar to other
anticholinergic drugs.
Anticholinergics for Treating Motion Sickness
® The effects of anticholinergics on the
CNS benefit patients who are prone to
motion sickness.
® Scopolamine
- Antihistamine for motion sickness.
- Available topically as skin patch
(Transderm Scop) that is placed
behind the ear
® Prevention of motion sickness is also
provided via wrist bands and ginger,
including ginger gum or candy.
® Transdermal scopolamine is delivered
over 3 days and is frequently
prescribed for activities such as flying,
cruising on the water, and bus or
automobile trips.
® Other drugs classified as
antihistamines for motion sickness are
(1) Dimenhydrinate (Dramamine)
(2) Cyclizine (Marzine)
(3) Meclizine hydrochloride
(Antivert).
These drugs can be used alone in early
stages of parkinsonism.
SANCO, RC
12
MSU-IIT
College of Nursing
NSG105: Pharmacology
Lorie Ann S. Balili, MAN, CNN, RN
® Most of these drugs can be purchased
OTC, with the exception of Transderm
Scop.
Note: Anticholinergic drugs can increase
intraocular pressure, they should not be
administered to patients diagnosed with
glaucoma
Side Effects and Adverse Reactions
® Side effects of antihistamines used as
anticholinergics include:
(1) Dry mouth
(2) Visual disturbances (especially
blurred vision resulting from
pupillary dilation)
(3) Constipation secondary to
decreased GI peristalsis
(4) Urinary retention related to
decreased bladder tone
(5) Tachycardia (when taken in
large doses)
(6) Hypotension
(7) Skin rash
(8) Muscle weakness
(9) Flushing
1.
2.
3.
NCLEX STUDY QUESTIONS
A patient is receiving bethanechol
(Urecholine). The nurse realizes that
the action of this drug is to treat which
condition?
a. Glaucoma
b. Urinary retention
c. Delayed gastric emptying
d. Gastroesophageal reflux
disease
The nurse teaches the patient receiving
atropine (Atreza) to expect which side
effect?
a. Diarrhea
b. Bradycardia
c. Blurred vision
d. Frequent urination
When benztropine (Cogentin) is
ordered for a patient, the nurse
acknowledges that this drug is an
effective treatment for which
condition?
a. Parkinsonism
b. Paralytic ileus
c. Motion sickness
d. Urinary retention
4.
Dicyclomine (Bentyl) is an
anticholinergic, which the nurse
realizes is given to treat which
condition?
a. Mydriasis
b. Constipation
c. Urinary retention
d. Irritable bowel syndrome
5. The nurse realizes that cholinergic
agonists mimic which parasympathetic
neurotransmitter?
a. dopamine
b. acetylcholine
c. cholinesterase
d. monoamine oxidase
6. The nurse is administering bethanechol
(Urecholine), a cholinergic agonist, and
should know that the expected
cholinergic effects include which of the
following?
a. Increased heart rate
b. Decreased peristalsis
c. Decreased salivation
d. Increased pupil constriction
7. When a patient has a cholinergic
overdose from excessive dosing of
bethanechol (Urecholine), the nurse
anticipates administration of which
drug as the antidote?
a. atropine
b. tolterodine
c. benztropine
d. metoclopramide
SANCO, RC
13