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CNS STIMULANTS. SAMUEL AGUAZIM. What is the definition of a CNS stimulant?. A CNS stimulant is a drug that increases motor activity, causes excitement and decreases feelings of fatigue. CNS stimulants include the methyxanthines, nicotine, and the amphetamines. CNS stimulant.

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CNS STIMULANTS

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CNS STIMULANTS

SAMUEL AGUAZIM


What is the definition of a CNS stimulant?

  • A CNS stimulant is a drug that increases motor activity, causes excitement and decreases feelings of fatigue.

  • CNS stimulants include the methyxanthines, nicotine, and the amphetamines


CNS stimulant

  • PSYCHOMOTOR STIMULANTS

  • CAUSE EXCITEMENT & EUPHORIA

  • INCREASE MOTOR ACTIVITY

  • PSYCHOTOMIMETIC DRUGS

  • PROFOUND CHANGES IN THOUGHT PATTERNS AND MOOD

  • FEW DRUGS USED CLINICALLY

  • IMPORTANT AS DRUGS OF ABUSE


METHYLXANTHINES

  • What are methyxanthines? A group of psychomotor stimulants include:

  • Caffeine

  • Theophylline

  • Theobromine ( found in cocoa but of little interest)


How do methyxanthines work?

  • Research indicates that methyxanthines increases cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) by inhibiting phosphodiesterase and blocking adenosine receptors.


CAFFEINE

  • What are the physiologic effects of caffeine?

  • Caffeine effects a number of organ systems within the body:

  • CNS- caffeine increases motor activity and alertness

  • Cardiovascular- caffeine increases heart rate and contractility


CAFFEINE

  • Smooth muscle- caffeine and its derivatives relax the smooth muscles of the bronchioles.

  • Genitourinary- caffeine can ac as weak diuretic and increase urinary output of Na+, CI- and K+

  • Gastrointestinal – caffeine stimulates secretion from the gastric mucosa. Therefore, patients who have peptic ulcer disease should be counseled to avoid caffeine


Adverse Effects of chronic caffeine use?

  • At low doses- insomnia and agitation can occur

  • At higher doses (8-10g)- Emesis, convulsion and even cardiac arrhythmias can occur.

  • Do methyxanthines cross the placenta?

  • Yes, and they are secreted into the mother’s milk. Patients should be advised to avoid them during pregnancy and while nursing


THEOPHYLLINE

  • THERAPEUTIC ROLE OF THEOPHYLLINE:

  • It can be used in the treatment of asthma, but currently it is not being used frequently because it has a very narrow therapeutic index and is not effective as the new beta agonist


NICOTINE

  • How are the physiological effects of nicotine related to the dose?

  • In low doses, nicotine causes ganglionic stimulation by depolarization.

  • At high doses it causes ganglionic blockade


NICOTINE

  • What are the physiologic actions of nicotine on the central nervous system?

  • At low doses- arousal, relaxation and improved attention

  • At high doses- central respiratory paralysis caused by disruption of medullary function


NICOTINE

  • How does nicotine affect the peripheral nervous system?

  • At low doses- increase in blood pressure and heart rate; constriction of blood vessels to the digits and impairment of flow

  • At high doses- decrease in blood pressure and in action of GI and GU tract due to ganglionic blockade

  • NOTE: NICOTINE HAS NO THERAPEUTIC USES


NICOTINE

  • What is nicotine’s route of administration?

  • Absorption occurs through oral mucosa by inhalation and transdermally.

  • What are its adverse effects?

  • CNS- irritability and tremors

  • Peripheral- intestinal cramps, diarrhea, and increased heart rate and blood pressure


NICOTINE

  • What withdrawal symptoms do nicotine addicts experience?

  • A craving for tobacco is accompanied by irritability, restlessness, anxiety and gastrointestinal pain.


AMPHETAMINES

  • Name three examples of this drug class.

  • 1. methylphenidate ( ritalin)

  • 2. methamphetamine ( methedrine)-”speed”

  • 3. dextroamphetamine ( dexedrine)


AMPHETAMINES

  • How do these drugs work?

  • Amphetamines work by releasing neuronal stores of catecholamines especially norepinephrine and dopamine


AMPHETAMINES

  • What are the physiologic actions of these drugs?

  • Euphoria

  • Decrease in fatigue

  • Increase in blood pressure

  • Increase in rate of respiration

  • Decrease in appetite


AMPHETAMINES

  • What is their clinical use?

  • Attention deficit hyperactivity disorder(ADHD)-METHYLPHENIDATE is used to alleviate this problem

  • Appetite control- amphetamines decrease appetite by blocking the receptors in the lateral hypothalamus

  • Narcolepsy


AMPHETAMINES

  • What is the route of administration? Oral

  • Where are amphetamines metabolized? In the liver

  • Does physiologic and psychological dependence occur with amphetamine use?

  • Yes- amphetamines can be very addictive


AMPHETAMINES

  • What are the adverse effects of these drugs?

  • Amphetamines like caffeine and nicotine affects multiple organ systems.

  • CNS-insomnia, irritability, convulsions; chronic use can lead to a psychotic state resembling schizophrenia

  • Gastrointestinal- anorexia, nausea, dry motuh

  • Cardiovascular- palpitations, angina, arrhythmias, hypertension


AMPHETAMINES

  • Amphetamines are contraindicated with what group of drugs?

  • The monoamine Oxidase (MAO) inhibitors

  • How is amphetamine overdose managed?

  • Chlorpromazine is beneficial in amphetamine overdose because it blocks the alpha receptors which are responsible for the CNS disturbances and hypertension


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