Ch 17 - CNS Stimulants - DONE Flashcards
What is the definition of CNS stimulants?
A CNS stimulant is a drug that increases motor activity, causes excitement, and decreases the feelings of fatigue.
Give examples of CNS stimulants:
- Methylxanthine
- Nicotine
- Amphetamine
What are Methylxanthines?
A group of psychomotor stimulants including:
- Caffeine
- Theophylline
- Theobromine (found in cocoa)
How do Methylxanthines work?
Methylxanthines increase cGMP and cAMP by inhibiting phosphodiesterase and blocking adenosine receptors
What are the physiological effects of caffeine?
CNS
Caffeine increases motor activity and alertness
What are the physiological effects of caffeine?
Cardiovascular
Caffeine increase the heart rate and contractility
What are the physiological effects of caffeine?
Smooth muscle
Caffeine and its derivatives relax the smooth muscle of the bronchioles
What are the physiological effects of caffeine?
Genitourinary
Caffeine can act as weak diuretics and increase urinary output of Na+, Cl-, and K+
What are the physiological effects of caffeine?
GI
Caffeine stimulates secretion of HCL from the gastric mucosa. Therefore patients who have peptic ulcer disease should be counseled to avoid caffein
What are the adverse effect of chronic use of caffeine?
- at low doses: insomnia and agitation can occur
- at higher doses: emesis, convulsion, and even cardiac arrhythmias can occur
Do the Methylxanthines 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.
What is the therapeutic role of Theophylline?
Theophylline can be used in the treatment of asthma, but currently it is not being frequently used because it has a very narrow therapeutic index and is not as effective as the new β agonists
How are the physiological effect of nicotine related to the dose?
- low doses: nicotine causes ganglionic stimulation by depolarization
- high doses: nicotine causes ganglionic blockade
What are the physiologic actions of nicotine on the CNS at low doses?
- arousal
- relaxation
- improved attention
What are the physiologic actions of nicotine on the CNS at high doses?
central respiratory paralysis caused by disruption of medullary function
How does the nicotine affect the peripheral nervous system at low doses?
- increase in BP and HR
- constriction of blood vessels to the digits and impairment of flow
How does the nicotine affect the peripheral nervous system at high doses?
decrease in BP and in action of GI and GU tract due to ganglionic blockade
GU tract =
genitourinary tract
What are nicotine´s therapeutic use?
As an ingrediant of a transdermal patch or chewing-gum, low-dose nicotine is used to help with smoking cessation
Name three amphetamines:
- methylphenidate
- methamphetamine
- dextroamphetamine
How do amphetamine work?
Amphetamines work by releasing neuronal stores of catecholamines, especially norepinephrine and dopamine
What are the physiological action of amphetamine?
- euphoria
- decrease in fatigue
- increase in BP
- increase in rate of respiration
- decrease in appetite
What is the clinical use of amphetamine?
- ADHD
- Appetite control
- Narcolepsy
What is used to treat ADHD?
methylphenidate (an amphetamine)
What is used to control the appetite?
Amphetamines decrease appetite by blocking the receptors in the lateral hypothalamus
What is used to treat narcolepsy?
Amphetamines
What is the route of administration of Amphetamines?
oral
where are Amphetamines metabolised and excreted?
- metabolised in the liver
- excreted in the urine
Does physiological and psychological dependence occur with Amphetamines use?
Yes, Amphetamines can be very addictive
Amphetamines AE:
CNS
- insomnia
- irritability
- convulsions
- chronic use can lead to a psychotic state resembling Schizophrenia
Amphetamines AE:
GI
- anorexia
- nausea
- dry mouth
Amphetamines AE:
Cardiovascular
- palpitations
- angina
- arrhythmias
- hypertension
With what group of drugs are Amphetamines CI with?
The monoamine oxidase (MAO) inhibitors
How is Amphetamines overdose managed?
Chlorpromazine in beneficial in Amphetamines overdose because it blocks the α receptors which are responsible for the CNS disturbances and hypertension
