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Pharm Block 3 > 6 - CNS Stimulants > Flashcards

6 - CNS Stimulants Flashcards

1
Q

What are the effects of CNS stimulants? What can they cause and what can they be used to treat?

A

Increase activity of CNS neurons through enhancement of excitation or suppression of inhibition.

In high enough doses all CNS stimulants can cause convulsions.

Can be used to treat ADHD and narcolepsy.

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2
Q

Describe the structure of caffeine? Where is it found?

A

It’s a methylxanthine similar in structure to purines.

Found in coffee beans, cocoa beans, and kola nuts.

Theophylline and theobromine are very similar in structure and mechanism (found in tea).

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3
Q

What is the mechanism of action of caffeine? What is the function of these receptors normally and what effect does caffeine have on them?

A

It’s a competitive antagonist of adenosine receptors.

Postsynaptic adenosine receptors make IPSPs (hyperpolarize) and presynaptic inhibit glu release.

Caffeine inhibits these inhibitory effects –> CNS stimulation

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4
Q

What effect does caffeine have at higher doses?

A

Inhibits cAMP phosphodiesterases to increase cAMP. Responsible for beneficial effects in treatment of asthma.

Induces release of Ca2+ from intracellular (ER) stores.

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5
Q

What are the pharmacological actions of caffeine when delivered in caffeine-containing drinks?

A

Increased alertness, increased attention during sustained tasks.

Decreased fatigue/drowsiness.

Can cause nervousness, restlessness, tremors.

High doses stimulate medullary respiratory and CV centers.

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6
Q

What are the peripheral effects of caffeine?

A

Positive ionotropic and chronotropic effects (direct effect on myocardium)

Dilates coronary and systemic vessels and constricts cerebral vessels.

Diuresis and increased gastric secretions. Modest bronchodilation.

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7
Q

What is the therapeutic usefulness of caffeine? What results from overdose?

A

Used in aid to stay awake.
Added to some aspirin to treat headahce (Excedrin)

Overdose: excessive CNS stim- nervousness, insomnia, excitement.

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8
Q

What are consequences of chronic caffeine use?

A

Tolerance
Physical dependence: develops at a dose of 2 cups/day
Withdrawal: symptoms include feelings of fatigue and sedation, headaches, nausea

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9
Q

How do sympathomimetic stimulants work? What are three examples of this type of drug?

A

Act through enhancement of catecholaminergic neurotransmission.

Cocaine, amphetamines, methylphenidate.

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10
Q

What are the chemical characteristics of cocaine? What are the three major forms?

A

Weak base, therefore unionized in the unprotonated form (B) which predominates at alkaline pH

Major forms: hydrochloride salt; purified free base; and impure base (“crack”)

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11
Q

How is the free base form of cocaine made? How is crack made?

A

By extracting the hydrochloride salt from an alkaline solution into an organic solvent.

Crack made by adding bicard to the hydrochloride salt.

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12
Q

What forms of cocaine are absorbed more quickly? Why is this?

A

Both crack and free base forms are absorbed more quickly across membranes.

They are more volatile than salt form, so they can be smoked - this method is preferred because it can get to the brain more quickly.

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13
Q

What are the pharmacokinetics of cocaine? How is it absorbed and how it is metabolized?

A

Well absorbed through mucous membranes with time to peak affect and duration of action dependent upon route of admin (shortest IV and smoked)

Metabolized in plasma and liver. Plasma 1/2 life of 50 min and CNS half life of 10-30 min.

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14
Q

What is the mechanism of action of cocaine?

A

Potent inhibitor of the reuptake of norepi, dopamine, and serotonin.

Binds transporter itself and inhibits binding of nts.

Increases activity of tyrosine and trp hydroxylase due to loss of end-product inhibition.

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15
Q

What are the non-recreational uses of cocaine?

A

It’s a local anesthetic and vasoconstrictor.

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16
Q

What three separate effects result from the inhibition of reuptake of norepi and dopamine with the use of cocaine?

A
  1. Peripheral sympathomimetic effects due to inhibition of NE reuptake in periphery: vasocontriction, tachy
  2. Increased alertness and vigilance due to inhibition of NE reuptake in CNS synapse
  3. Euphoria, elation, feeling of well being due to inhibition of DA reuptake in the mesolimbic circuit
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17
Q

What are the toxic effects of cocaine?

A

Neurotoxicologic consequences with long term use due to damage of dopaminergic neurons.

Overdose can cause seizures and CV effects

Developing fetus (more than alcohol): premature labor, low birth weight, learning, attachment disorder and emotional problems.

18
Q

Describe the profound psychological dependence that results from cocaine use? What are withdrawal symptoms?

A

Drug craving and drug seeking: users crave drug even 10 min after last dose.

Abuse liability grater with rapid delivery (smoking or IV)

Withdrawal: dysphoria, depression, sleepiness, fatigue.

19
Q

What is the structure of amphetamine and methamphetamine?

A

Structurally similar to norepi, weak bases.

Well absorbed orally, free base of meth can be smoked (“crystal meth”).

20
Q

What is the metabolism of amphetamine and methamphetamine? What is their half life?

A

Amphetamine metabolized to a variety of metabolites about about 50% excreted unchanged.

Methamphetamine is metabolized to amphetamine.

Relatively long half lives (longer than cocaine).

21
Q

What is the mechanism of action of amphetamine and methamphetamine?

A

Binds trace amine associated receptor (TAAR1), a GPCR that via cAMP/PKA phosphorylates reuptake carriers (DAT, NET, SERT) and VMAT2.

Results in inhibition of uptake of NE, DA, and 5HT and REVERSE the release of amines from terminal or vescicles (VMAT2).

Potentiates NE, DA, and 5HT signaling.

22
Q

What are the other mechanisms of action of amphetamine and methamphetamine beside binding to TAAR1? How does its effects compare to that of cocaine?

A

Partial agonist of alpha receptors

MAO inhibitor at high doses

Has most NE-like effects than cocaine.

23
Q

What are the side effects of amphetamine and methamphetamine?

A

Arousal, wakefulness, decreased fatigue.
Enhance athletic and intellectual performance (quantity not quality).

Elevated mood, increased self-confidence.

Resp stimulant, decrease appetite, peripheral sympathomimetic.

24
Q

Name three CNS stimulants and how they differ from each other?

A
  1. Amphetamine: mixture of stereoisomers - active form dextroamphetamine
  2. Methylphenidate: not technically an amphetamine but structually and mechanistically similar
  3. Methamphetamine: gets into brain better, higher abuse potential
25
Q

What are three clinical uses of amphetamines and methylphenidate?

A
  1. Narcolepsy for daytime “sleep attacks” - complicated by risk of abuse/tolerance
  2. ADHD for excessive motor activity, racing thoughts, difficulty w/ sustained attention
  3. Exogenous obesity - considered to be outside of control of individual
26
Q

What are side effects of amphetamine and methylphenidate taken at therapeutic doses?

A 
Insomnia
Abdominal pain
Anorexia, weight loss
Suppression of growth
High body temp
Facial tics
27
Q

Describe the toxicity of amphetamines and methylphenidate (that occurs at much higher doses than used for ADHD)?

A
  1. Acute toxicity: sympathomimetic effects-restlessness, dizzy, tremor
  2. Psychosis from excessive DA
  3. Neurotoxicity: permanent intellecutal problems, neuronal degeneration
  4. Meth mouth- severe tooth decay
  5. Abuse liability worse than cocaine
  6. Sudden cardiac death due to sympathetic activation
28
Q

There’s an FDA black box warning for use of methamphetamine in _______. Why is this?

A

Obesity.

This is due to its high potential for abuse.

29
Q

What three drugs are used to treat ADHD that are NOT classified as stimulants?

A

Atomoxetine: SNRI; antidepressant

Clonidine, guanfacine: alpha 2 adrenergic receptor agonists.

30
Q

What is nicotine? What is its mechanism of action?

A

Naturally occurring alkaloid in tobacco plants.

Agonist of nicotinic cholinergic receptors.

31
Q

What effect does nicotine have at the neuromuscular junction and autonomic ganglia?

A

NMJ: initially activates muscle contraction but then desensitizes

Autonomic ganglia: sympathetic-release of epi from adrenal. parasympathetic- stimulates GI. increased motility

32
Q

Where are nicotinic receptors found in the CNS? Describe them

A

Found in many brain regions including nucleus accumbens (reward center)

Monovalent cation channels, activation produces a membrane depolarization and thus neuronal excitation.

33
Q

What are the pharmacological actions of nicotine?

A
  1. CNS stimulant increases alertness
  2. Increases dopamine release in limbic, reward centers (reinforcing)
  3. Muscle relaxant
  4. Activates chemoreceptor trigger zone causing nausea
34
Q

Why is smoked nicotine highly reinforcing?

A
  1. Reaches brain rapidly (~7 sec)
  2. Increases DA signaling in n. accumbens - reward pathway
  3. Each puff is separate chance for brain to associate smoking with reward, therefore highly addictive.
35
Q

What tolerance is associated with nicotine?

A

Tachyphylaxis: tolerance occurs over a very short period of time (hours) and reverses itself over night.

This is why the first cigarette of the day is the best.

36
Q

What are symptoms of nicotine withdrawal?

A

Irritability, hostility, impatience.

Anxiety, depression, difficulty concentrating.

Increased appetite, weight gain.

37
Q

What is the treatment of nicotine dependence? What is the success of this?

A

Replacement most common

Active: nasal spray, gum, lozenge, inhaler, sublingual.
Passive: patches.

Lg percent of pts using replacement are not smoking in 6 wks but only 20% are abstinent for 1 year.

38
Q

What antidepressant can be used for smoking cessation? How does it work and what are the side effects?

A

Bupropion

Used as sustained release to reduce cravings and lessen some withdrawal symptoms (depression).

Side effects: dry mouth and insomnia

39
Q

What partial agonist of nicotinic receptors can be used to treat nicotine use? How does it work? How does this drug compare to others for smoking cessation?

A

Varenicline

Reduces craving by activating the nAChR; will not desensitize like nicotine itself. Also blocks effects of nicotine if person smoked (partial antagonist effect)

More efficacious than placebo and buproprion at 12 and 24 wks.

40
Q

What are the side effects of Varenicline (used for smoking cessation)?

A

Nausea, insomnia, headaches, and constipation.

Recent FDA concern: increased suicidal thoughts and depression.

Pharm Block 3 (15 decks)

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