Download Autonomic Pharmacology

Chapter 5
Autonomic Drugs
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Autonomic Pharmacology
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Autonomic Nervous System
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This system is divided into two separate systems.
These systems are called the parasympathetic
nervous system and the sympathetic nervous
system.
These systems often produce opposite effects.
Drugs in this group are designed to either
enhance or mimic the autonomic nervous system
or to block the effects of the neurotransmitters at
their receptor sites.
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Autonomic Nervous System
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Parasympathetic Nervous System
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This system is concerned with the
conservation of the body processes.
Its main neurotransmitter is acetylcholine.
Its receptors are muscarinic, nicotinic, and the
somatic-skeletal muscles.
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Autonomic Nervous System
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Sympathetic Nervous System
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This nervous system is designed to cope with
emergency situations.
This is commonly known as the “fright or flight”
response.
Its neurotransmitters are epinephrine and
norepinephrine.
Its receptors are the α and β receptors.
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Autonomic Pharmacology
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Cholinergic or Parasympathomimetic Drugs
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These drugs are classified as either direct or indirect
acting agents.
 Direct acting drugs act directly on the
parasympathetic receptors.
 Indirect acting drugs work by either of two methods.
 They can cause the release of the neurotransmitter
which then goes to the receptor site or they inhibit the
enzyme cholinesterase.
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Autonomic Pharmacology
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Cholinergic Pharmacology
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Cardiovascular
• Direct effects include negative chronotropic and
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inotropic actions.
Relaxation of smooth muscles causes a decrease in
total peripheral resistance.
Indirect effects include increased heart rate and
cardiac output.
The resulting effect depends upon the dose used.
Usually, the patient experiences bradycardia and a
decrease in blood pressure and cardiac output.
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Autonomic Pharmacology
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Cholinergic Pharmacology
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Gastrointestinal
• These drugs excite the smooth muscle of the
gastrointestinal tract and cause an increase in
activity, motility, and secretion.
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Eye
• These drugs cause miosis and cycloplegia.
• They cause a decrease in intraocular pressure.
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Autonomic Pharmacology
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Adverse Reactions
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Adverse reactions are an extension of the
drugs’ pharmacologic effects.
They include:
• Salivation
• Lacrimation
• Urination
• Defecation
• Paralysis
• Overdose
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Cholinergic Pharmacology
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Contraindications
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The contraindications and relative cautions are
a result of the drug’s pharmacologic and
adverse effects.
They include:
• Bronchial asthma
• Hyperthyroidism
• Gastrointestinal or urinary tract obstruction
• Myasthenia gravis treated with neostigmine
• Peptic ulcer disease
• Severe cardiac disease
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Cholinergic Drugs
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Anticholinergic Drugs
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These drugs prevent the action of
acetylcholine at postganglionic
parasympathetic endings.
Acetylcholine is released but its receptor site
is completely blocked by anticholinergic
drugs.
These drugs only block muscarinic receptors.
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Anticholinergic Drugs
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Pharmacology
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Central Nervous System
• Depending on the dose, these drugs can cause
stimulation or depression.
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Exocrine Glands
• They reduce the flow and volume of secretions in the
respiratory, gastrointestinal, and genitourinary tracts.
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Anticholinergic Drugs
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Pharmacology
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Smooth Muscle
• Relax smooth muscles in the respiratory and
gastrointestinal tracts.
• They delay gastric emptying and decrease
esophageal and gastric emptying.
• These drugs also cause bronchial dilation.
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Eye
• These drugs cause mydriasis and cycloplegia.
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Anticholinergic Drugs
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Pharmacology
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Cardiovascular
• With large doses, these drugs produce vagal
blocking which results in tachycardia.
• Bradycardia can occur with low doses.
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Anticholinergic Drugs
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Adverse Reactions
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The adverse reactions are an extension of the
drugs’ pharmacologic effects.
They include:
• Xerostomia
• Constipation
• Urinary retention
• Blurred vision
• Hyperpyrexia
• Hallucinations
• Photophobia
• Tachycardia
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Anticholinergic Drugs
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Contraindications
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Contraindications are usually due to the drugs’
pharmacologic and adverse effects.
They include:
• Glaucoma
• Prostatic hypertrophy
• Intestinal or urinary obstruction or retention
• Cardiovascular disease
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Anticholinergic Drugs
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Uses
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Preoperative Medication
• They inhibit salivary and bronchial secretions.
• They block the vagal slowing of the heart that can
occur with general anesthesia.
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Gastrointestinal Disorders
• They decrease gastrointestinal motility and can be
used to treat ulcers, diarrhea, and hypermotility.
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Anticholinergic Drugs
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Uses
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Ophthalmologic Examinations
• Topical use can cause mydriasis which causes a full
visualization of the retina.
• Cycloplegia relaxes the lens so that proper
prescriptions for glasses can be determined.
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Parkinson Disease
• They reduce the tremors and rigidity associated with
Parkinson and drug-induced Parkinson disease.
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Anticholinergic Drugs
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Uses
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Motion Sickness
• These drugs are used to treat or prevent motion
sickness because of their central nervous system
depressant action.
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Dentistry
• These drugs are used to create a dry, oral field.
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Adrenergic Drugs
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Adrenergic drugs can be classified as having direct
action, indirect action, or mixed action.
These drugs stimulate α and β receptors throughout
the body.
Drugs with direct action (epinephrine, norepinephrine,
isoproterenol) produce their effect by directly
stimulating the receptor site.
Drugs with indirect action (amphetamine) release
endogenous norepinephrine which then stimulates
the receptor.
Drugs with mixed action (ephedrine) either directly
stimulate the receptor or release endogenous
norepinephrine.
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Adrenergic Drugs
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Pharmacology
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Central Nervous System (CNS)
• These drugs produce CNS excitation or alertness.
• Higher doses produce anxiety, apprehension,
restlessness, and tremors.
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Cardiovascular System
• These drugs increase the force and rate of
contraction of the heart.
• Blood pressure is also increased.
• Total peripheral resistance is also increased.
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Adrenergic Drugs
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Pharmacology
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Eye
• These drugs lower intraocular pressure and can cause
mydriasis.
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Respiratory System
• These drugs cause a relaxation of bronchiole smooth
muscles.
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Metabolic Effects
• Increased glycogenolysis from β-receptor stimulation
causes hyperglycemia.
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Salivary Glands
• These drugs produce vasoconstriction of the salivary
glands which leads to decreased salivary flow which
results in xerostomia.
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Adrenergic Drugs
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Adverse Reactions
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The adverse reactions associated with these
drugs are an extension of the drugs’
pharmacologic effects.
They include:
• Anxiety
• Tremors
• Tachycardia
• Increased blood pressure
• Arrhythmias
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Adrenergic Drugs
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Uses
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Vasoconstriction
• These drugs are used in dentistry because of their
vasoconstrictive actions on blood vessels. They are
added to local anesthetics because they prolong the
action of the local anesthetic, reduce the risk for
systemic toxicity, and help to create a dry field.
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Cardiac Effects
• These drugs are used to raise blood pressure and to
treat cardiac arrest.
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Adrenergic Drugs
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Uses
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Bronchodilation
• These drugs are used to treat asthma, emphysema,
and allergic reaction.
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Central Nervous System Stimulation
• These medications are used for the treatment of
attention deficit hyperactivity disorder, narcolepsy,
and as diet aids.
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Adrenergic Blocking Drugs
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These drugs competitively inhibit α and β
receptor sites.
One group of drugs is specific for α
receptors.
One group of drugs is specific for both β1
and β2 receptors.
One group is specific for β2 receptors.
One group is specific for both α and β
receptors.
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Antiadrenergic Drugs
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Pharmacology
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These drugs reduce sympathetic tone in the
blood vessels and decrease total peripheral
resistance.
This results in a reduction in blood pressure.
Uses
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These drugs are used to treat hypertension,
peripheral vascular disease (i.e., Raynaud
syndrome) and benign prostatic hypertrophy.
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