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Pharm > CNS Stimulants > Flashcards

CNS Stimulants Flashcards

1
Q

CNS Stimulants:
General properties

A
  1. Increase activity of CNS neurons
  2. Can either enhance excitation or suppress inhibition
  3. In sufficient doses, all stimulants can produce convulsions
  4. CNS stimulants have limited clinical usefulness
    • Attention-deficit, hyperactivity disorder
    • Narcolepsy
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2
Q

Caffeine:

A
  • methylxanthine compound found in coffee
  • found in cocoa and the kola nut
    • theophylline & theobromine are found in tea leaves
  • A cup or mug of coffee may have 80 to 200 mg of caffeine
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3
Q

Caffeine:

Mechanism of Action

A
  1. Block adenosine receptors (equilibrium-competitive antagonist)
    • Postsynaptic adenosine receptors produce IPSP’s
    • Presynaptic adenosine receptors inhibit glutamate release
    • Caffeine blocks both of these inhibitory effects (disinhibition) resulting in CNS stimulation
  2. Inhibition of phosphodiesterase
    • Results in increased cAMP concentrations
    • property of these compounds that results in benefit for asthma
  3. Induces release of calcium from intracellular stores (endoplasmic reticulum)
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4
Q

Caffeine:

Pharmacological of Action

A
  1. CNS stimulant:
    • increased alertness and capacity or tasks requiring sustained attention
    • Decreased fatigue and drowsiness
    • Can cause nervousness, restlessness and tremors
    • High doses can stimulate medullary respiratory, vasomotor and vagal centers
  2. Peripheral actions:
    • Stimulates myocardium - positive chronotropic & inotropic effects
    • Dilates coronary and general systemic blood vessels
      • constricts cerebral blood vessels
      • may underlie its usefulness in headache
    • Diuretic effect
    • Increases gastric secretion
    • Modest bronchodilator activity
      • not as much as theophylline
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5
Q

How is caffeine therapeutically useful?

A
  1. Used as an aid to stay awake
  2. Treatment of headache
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6
Q

Caffeine:

Toxicity and chronic use

A
  1. Toxicity/overdose results in:
    • excessive CNS stimulation, nervousness, insomnia, excitement
  2. Chronic use
    • Tolerance develops to stimulant effects of caffeine
    • Physical dependence develops at a dose of two cups of coffee a day
    • Withdrawal symptoms: fatigue/sleepiness; headaches; nausea; vomiting (rare)
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7
Q

Defintion: Sympathomimetic Stimulants

A

Compounds that act through the enhancement of catecholaminergic neuro-transmission

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8
Q

Cocaine:

Chemistry

A
  1. Weak base, unprotonated form is unionized
    • this form predominates at alkaline pH
  2. Used in two major forms:
    1. cocaine hydrochloride: water soluble
    2. cocaine free base: lipid soluble, volatile
  3. free base is made by extracting cocaine base from an alkaline solution into ether
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9
Q

Cocaine:

Pharmacokinetics and Metabolism

A
  1. Well absorbed through most mucous membranes
    • including the lungs
  2. Time to peak effect and duration of action are dependent on route of administration
    • ​Shorter for IV & smoked cocaine
  3. Metabolized primarily by serum and liver esterases
    • Can also be demethylated at the nitrogen
    • Very short half-life (50 min)
  4. Testing for cocaine use: look for metabolites in urine
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10
Q

Cocaine:

Mechanisms of Action

A
  1. Cocaine is a potent inhibitor of the reuptake of:
    • norepinephrine, dopamine and serotonin
  2. Cocaine receptor on transporter for dopamine, competes for binding of the endogenous ligand ⇒ increased ligand in the synapse
  3. Central reinforcing effects
    • believed due to an action on dopamine synapses in the ventral striatum
  4. Increases tyrosine and tryptophan hydroxylase
    • loss of endproduct inhibition
  5. Local anesthetic; vasoconstrictor
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11
Q

Cocaine:

Pharmacological Effects

A
  1. Peripheral sympathomimetic
    • due to increased norepinephrine
    • vasoconstriction; tachycardia
  2. Increased alertness; vigilance
    • increased NE in CNS
  3. Produces euphoria, feelings of elation, well being and competency
    • Due to ↑ DA in mesolimbic circuit
    • High abuse potential - very reinforcing
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12
Q

Cocaine:

Toxicity and chronic use

A
  1. Tolerance and physical dependence occurs with heavy use
  2. Withdrawal syndrome – mild
  3. Neurotoxicological effects
    • possible damage to dopamine systems
  4. Overdose ⇒ seizures and/or cardiovascular effects
  5. Fetal effects are more significant than alcohol
    • Low birth weights
    • Learning and emotional problems
    • Attachment disorder
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13
Q

Cocaine Abuse:

A
  • **Psychological dependence: **
    • High abuse liability
    • Very reinforcing
    • Results in drug craving and drug seeking
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14
Q

Why would you use cocaine clinically?

A
  • Local anesthesia in upper respiratory tract
    • also decreases blood flow
    • useful for nose surgery
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15
Q

Amphetamine and amphetamine-like drugs:
Chemistry

A
  • Most are α-methyl phenethylamine derivatives
  • Weak base
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16
Q

Amphetamine and amphetamine-like drugs: Pharmacokinetics and Metabolism

A
  • Well absorbed orally
  • Longer duration of action than cocaine
    • 4-6 hours orally
  • Metabolism
    • Deamination to benzoic acid (predominant route)
    • Also excreted unchanged as amphetamine base excretion increased in acid urine
17
Q

**Amphetamine and amphetamine-like drugs: **

Mechanisms of action

A
  1. Releases norepinephrine, dopamine and serotonin
  2. Blocks transmitter uptake into presynaptic terminals (like cocaine)
  3. Direct partial agonist of alpha-adrenergic receptors
  4. MAO inhibition (at high doses)
  5. More NE-­‐like effects than cocaine
18
Q

Amphetamine and amphetamine-like drugs: Pharmacological properties

A
  • Wakefulness, alertness, decreased fatigue
    • more done, but more errors
  • Enhances athletic and intellectual performance
  • Elevation of mood; increased self-confidence
  • Increase in motor and speech activities; speed
  • Respiratory stimulation
  • Decrease in appetite
  • Peripheral sympathomimetic effects
19
Q

Amphetamine and amphetamine-like drugs:

Specific agents (3)

A

all have similar effects; however, intensity of central
effects vary

  1. Amphetamine and dextroamphetamine
  2. Methamphetamine - better CNS bioavailability, more CNS effect, higher abuse liability
  3. Methylphenidate - not actually an amphetamine but structurally and mechanistically very similar
20
Q

**Amphetamine and amphetamine-like drugs: **

Clinical uses

A
  1. Narcolepsy: day time “sleep attacks”
    • Amphetamine and dextroamphetamine
  2. Attention-deficit hyperactivity disorder
    • Amphetamine, dextroamphetamine and methylphenidate
    • Excessive motor activity, racing thoughts, difficulty in sustained attention
    • Academic underachievement
21
Q

What are side effects associated with amphetamine and amphetamine-like drugs?

A

Side effects:

  1. Insomnia
  2. Abdominal pain
  3. Anorexia, weight loss
  4. Suppression of growth
  5. Fever
  6. Facial tics
22
Q

Toxicity of amphetamines and methylphenidate:

A
  1. Acute toxicity
    • Sympathomimetic effects
    • Restlessness, dizziness, tremor
  2. Psychosis (due to excessive dopamine)
  3. Neurotoxicity: abuse can lead to permanent intellectual problems
  4. Abuse liability - very high
    • Particularly for IV or smoked methamphetamine
    • Abuse liability is similar to cocaine; clinical deterioration is worse because of neurotoxicity
23
Q

Nicotine:

Mechanism of Action

A

Agonist of nicotinic cholinergic receptors

  1. Neuromuscular junction - not as affected
  2. Autonomic ganglia
    • Sympathetic ganglia activation ⇒ release of epinephrine
    • Parasympathetic ganglia activation is predominant ⇒ GI effects (nausea; increased motility)
  3. CNS receptors
    • Found in many brain regions
    • Results in membrane depolarization (excitation)
24
Q

Nicotine:

Pharmacological actions

A
  1. CNS stimulant
    • Increased alertness
    • Activates dopamine signaling in nucleus accumbens
    • it is reinforcing
  2. Muscle relaxant
25
Q

Nicotine is absorbed readily through _____ _________.

A

mucous membranes

26
Q

How does nicotine affect the neuronal systems?

A
  • Nicotine is reinforcing
  • Activates neuronal systems designed to maintain behaviors that are important for survival
27
Q

Describe tolerance to nicotine:

A
  • Occurs over a very short time period
    • hours; tachyphylaxis
  • First cigarette of the day is the best
28
Q

Nicotine withdrawal symptoms:

A
  • Irritability, impatience, hostility
  • Anxiety
  • Depression
  • Difficulty concentrating
  • Increased appetite; weight gain
29
Q

How nicotine addiction commonly treated?

A

Nicotine replacement therapy:

  • Most widely used
  • Replace nicotine (partially)
  • Formulations:
    • Nasal spray
    • Gum
    • Lozenge
    • Sublingual tablet
    • Vapor inhaler
    • Patches (passive)
30
Q

Bupropion (Zyban®):

A
  • Mechanism of action - unknown
    • antidepressant
    • seems to enhance noradrenergic and dopaminergic signaling
  • Adverse effects
    • dry mouth, insomnia
  • Moderately effective
    • reduces craving and nicotine withdrawal symptoms
31
Q

Varenicline (Chantix™):

A
  • Partial agonist of CNS nicotinic receptors
    • ​Activates nicotinic receptors alone enough to reduce craving and withdrawal
    • Reduces the effects of the full agonist, nicotine
  • Produces significant increase in abstinence compared to placebo
  • Adverse effects
    • nausea; insomnia; headache; constipation
  • Recent FDA warning
    • ​increases thoughts of suicide; depression

Pharm (16 decks)

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