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Chapter 22
Drugs Stimulating the Central Nervous System
ASHA RUSSEL
ASST. SCIENCE TUTOR ‘A
Introduction
Many substances are used to stimulate the CNS.
These substances, sometimes called analeptics, include drugs that are used
for therapeutic effects and nontherapeutic effects.
Substances with therapeutic effects are categorized as (1) central, (2)
anorectic, or (3) respiratory stimulants.
Central and respiratory stimulants are generally used to stimulate the CNS.
The anorectic agents depress the appetite.
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Physiology
The CNS is responsible for providing control systems and surveillance for
many vegetative and conscious functions.
The control of respiration occurs in the pons and medulla.
CNS stimulants may provoke (1) an increased release of neurotransmitters,
(2) a decreased reuptake of neurotransmitters, or (3) an inhibition of
postsynaptic enzymes.
The result is a heightened postsynaptic response, leading to increased
arousal.
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Regulatory Centers of the Brain
Pathophysiology
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Attention Deficit Hyperactivity Disorder
Attention deficit hyperactivity disorder (ADHD) is the most prevalent
chronic health issue affecting school-aged children.
It is characterized by a persistent pattern of inattentiveness, hyperactivity,
and impulsivity.
The management of ADHD is complex but usually involves
pharmacotherapy with one or more of the CNS stimulants combined with
behavior modification.
Respiratory Stimulation
In patients at risk for postoperative pulmonary complications, respiratory
depression may be a complication arising from chronic obstructive lung
disease and frequent hypercapnia.
Hypercapnia is a buildup of carbon dioxide levels that may result from
pulmonary compromise.
Preterm infants may experience hypercapnia because of their immature
respiratory systems.
Pharmacologic management of respiratory depression includes
administering CNS stimulants, such as caffeine and doxapram.
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I. Centrally Acting CNS Stimulants
The centrally acting CNS stimulants are drugs that stimulate the CNS directly
or indirectly.
This group of drugs includes the (1) amphetamines, (2) methylphenidate,
(3) pemoline, and (4) cocaine.
Prototype drug: Dextroamphetamine (Dexedrine).
Drugs Significantly Different From Dextroamphetamine
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1. Atomoxetine (Strattera)
Is a selective norepinephrine reuptake inhibitor.
It is the first ADHD medication that is not a stimulant.
It is thought to involve the selective inhibition of the presynaptic
norepinephrine transporter.
Metabolism: Liver.
Contraindications: Concurrent use of MAOIs (only one).
1. Atomoxetine (Strattera)
Precautions:
Monitor liver enzymes because there is a high incidence of (1) liver damage,
(2) elevated liver enzymes, and (3) jaundice.
The drug may also increase blood pressure and heart rate and can cause
additive cardiovascular effects with albuterol and pressor agents.
Should be used cautiously in conditions that predispose patients to
hypotension because it has been reported to cause orthostatic hypotension
and syncope.
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1. Atomoxetine (Strattera)
Most Common Adverse Effects:
Constipation
Dry Mouth
Nausea
Appetite Suppression
Lethargy
Dizziness
Insomnia
Sexual Dysfunction
Urinary Dysfunction &
Dysmenorrhea.
1. Atomoxetine (Strattera)
Major Advantages:
It is not a stimulant.
It is not a DEA Schedule II drug &
The drug does not have be securely stored.
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2. Antihypertensive Agents
Antihypertensive agents such as clonidine and guanfacine may be
prescribed alone or with a stimulant to manage the symptoms of ADHD,
especially in children with tics.
These drugs help with impulsivity, sleep problems, frustration tolerance,
and activity.
They do not have any known effect on inattention.
Common adverse effects include (1) drowsiness, (2) dry mouth, and (3)
constipation.
3. Antidepressants
Antidepressants may be used in managing ADHD, especially if comorbid
diagnoses are suspected.
Tricyclic antidepressants, such as desipramine and imipramine improve
concentration, mood, and hyperactivity and help regulate emotional ups
and downs.
It is important to monitor cardiac activity, especially in children, when
patients are taking these drugs.
SSRIs, such as paroxetine and fluoxetine are used primarily when mood or
anxiety disorders are thought to coexist.
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3. Antidepressants
SSRIs may increase impulsivity.
Common adverse effects with antidepressant drugs include:
Many of these adverse effects abate after continued use of the drug.
Headache
Insomnia
Weight Loss
Nervousness &
Either Constipation or
Diarrhea.
II. Anorectic Agents
Obesity is a complex problem that is very difficult to treat.
Although drug therapy is helpful, drugs alone cannot manage weight loss.
Diet and exercise are equally important.
Prototype drug: Phentermine (Adipex-P).
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III. Respiratory Stimulants
Respiratory stimulants are used to manage postsurgical respiratory
depression and apnea in preterm neonates.
Prototype drug: Caffeine.
Caffeine: Core Drug Knowledge
Pharmacotherapeutics:
Caffeine is used in managing:
Neonatal apnea
Asthma
Drowsiness and
Fatigue.
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Caffeine: Core Drug Knowledge
Pharmacokinetics:
Route of administration: Oral or IV.
Peak Action: Within 50 to 75 minutes.
Distribution: Rapidly throughout the body; crosses the placenta and
bloodbrain barrier.
Metabolism: Liver (partially).
Excretion: Urine (unchanged & its metabolites).
Caffeine: Core Drug Knowledge
Pharmacodynamics:
Direct stimulant at all levels of the CNS, which also stimulates the
cardiovascular system.
Caffeine also stimulates the medullary respiratory center and relaxes
bronchial smooth muscle.
Caffeine stimulates voluntary muscle and gastric acid secretion, increases
renal blood flow, and is a mild diuretic.
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Caffeine: Core Drug Knowledge
Contraindications:
Caffeine is contraindicated for patients suffering from insomnia because
insomnia is one of its most frequent adverse effects.
Precautions:
Caffeine should be used cautiously in patients with anxiety disorders, panic
disorder, or both because as a CNS stimulant, it can aggravate these
conditions.
It should be prescribed cautiously to any patient with a seizure disorder.
Caffeine: Core Drug Knowledge
Precautions:
Caffeine should be given cautiously in patients with cardiac disease and
hypertension.
Caffeine should be used cautiously in patients with hepatic disease or
hepatic impairment.
Extra caution observed for use in neonates.
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Caffeine: Core Drug Knowledge
Adverse Effects:
Tremor
Sinus tachycardia,
Heightened attentiveness
Diarrhea
Excitement
Irritability
Insomnia
Headache
Muscle twitches &
Palpitations
Caffeine: Core Drug Knowledge
Drug Interactions:
Oral contraceptives
Psychostimulants
Sympathomimetic agents
Fluoroquinolone antibiotics
Lithium and
MAOIs
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Caffeine: Core Drug Knowledge
Patient and Family Education:
Convey to the patient that caffeine is a drug and as such may create
serious adverse effects.
Discuss potential adverse effects of the drug and ways to minimize their
potential.
Pg. No: 400
Drug Closely Related to Caffeine
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Doxapram (Dopram)
It is a parenteral analeptic agent.
Is used to (1) stimulate post-anesthesia respiratory depression or (2) drug
induced CNS depression and (3) to treat chronic pulmonary disease
associated with acute hypercapnia.
It works by activating the peripheral carotid chemoreceptors, thereby
increasing respiratory rate.
It is not usually the drug of choice because of its narrow margin of safety.
Doxapram (Dopram)
Adverse Effects:
Hypertension
Sinus tachycardia
Arrhythmias
Dyspnea
Headache
Dizziness
Convulsions
Tachypnea
Laryngospasm
Bronchospasm
Nausea & Vomiting
Diarrhea &
Urinary retention
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