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