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MWU Pharmacology I > Sympathomimetics > Flashcards

Sympathomimetics Flashcards

1
Q

Name the 3 direct acting endogenous catecholamines

A

1) Epinephrine
2) Norepinephrine
3) Dopamine

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2
Q

Name 2 nonselective direct acting beta agonists

A

1) Isoproterenol
2) Dobutamine

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3
Q

Name the short acting direct Beta 2-selective agonist

A

Albuterol

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4
Q

Name 2 direct, long acting Beta-2 selective agonists

A

1) Salmeterol
2) Formoterol

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5
Q

Name the Beta 3-selective direct agonist

A

Mirabegron

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6
Q

Name the direct acting alpha 1-selective agonist

A

Phenylephrine

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7
Q

What’s the mixed acting andrenergic agonist

A

Pseudoephedrine

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8
Q

Name 3 indirect acting adrenergic agonists

A

1) Amphetamine
2) Dextroamphetamine
3) Methylphenidate

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9
Q

Where are Alpha 1 receptors widely expressed? What does their activation lead to? Compare Alpha 2 to alpha 1.

A

Widely expressed in vascular beds

Vasoconstriction

Alpha 2 plays a minor role in vasoconstriction compared to alpha 1

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10
Q

Where are beta 2 receptors expressed and their roles?

A

Expressed in certain vascular beds (ie. skeletal muscle)
Activation leads to vasodilation

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11
Q

What is predominant cardiac adrenergic receptor. Which becomes more important during heart failure?

A

Beta 1 is the predominant cardiac
receptor

  • Beta 2 receptors become functionally
    more important in heart failure
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12
Q

What does beta adrenergic activation accomplish in the heart.

SA node / AV node / mycardium / physiologic effect

A
  • Sinoatrial node: increased pacemaker
    activity and heart rate (positive chronotropic effect)
  • Atrioventricular node: increased conduction velocity (positive dromotropic effect)
  • Myocardium: increased intrinsic contractility (positive inotropic effect)
  • Physiologic response: Increased cardiac output
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13
Q

Where are alpha 1 receptors primarily expressed in the heart? What does their activation lead to?

A
  • Alpha 1 receptors are expressed in the myocardium
  • Minor role in normal physiology
  • May become functionally more important in heart failure
  • Activation leads to: Minor increase in contractility (positive inotropic effect)
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14
Q

Epinephrine Mechanism of Action

A

Potent agonist of both alpha and beta receptors
- stimulates all alpha and beta receptors comparably

  • Complex effects on target organs
    • Most prominent actions are on the cardiovascular
      system
  • Potent vasopressor
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15
Q

What are the effects of epinephrine on the cardiovascular system

BP / Heart / Vasculature

A

Blood pressure
* Increased systolic pressure
* Decreased diastolic pressure (dose-dependent)
* MAP is largely unchanged: Thus, no compensatory
baroreceptor reflex

Heart
* Increased heart rate (chronotropic), contractile force
(inotropic), and cardiac output

Vasculature
* Constriction of most vascular beds
* Dilation of skeletal muscle blood vessels (dose-dependent)
* Net effect is a decrease in peripheral vascular resistance

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16
Q

What are some respiratory and metabolic effects of epinephrine

A

Respiratory effects
* Bronchodilation

Metabolic effects
* Hyperglycemia
* Stimulates gluconeogenesis and glycogenolysis
* Inhibits insulin release
* Lipolysis: Increased free fatty acids

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17
Q

Adverse effects of epinephrine

Minor and serios

A

Minor:
* Restlessness, throbbing headache, tremor, and palpitations

Serious:
* Cerebral hemorrhage: With large doses or rapid IV
injections
- Due to sharp rise in blood pressure
–NOTE: rapid IV administration
during pulseless arrest is necessary

  • Cardiac arrhythmias
  • Angina: In patients with coronary
    artery disease
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18
Q

Contraindications for epinephrine

A

Patients on nonselective beta blockers
* Result in unopposed activation of vascular alpha 1
receptors
* May lead to severe hypertension and cerebral
hemorrhage

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19
Q

Epinephrine therapeutic uses

allergic reaction / heart / eyes / anesthesiology

A

Hypersensitive reactions
* Provides rapid emergency relief to anaphylaxis
Bradyarrhythmias
* Restore rhythm in patients with cardiac arrest
Asystole/pulseless cardiac arrest

Ophthalmic uses
* Mydriatic agent for ocular surgery
* Glaucoma
- Mechanism is complex
- No longer commonly used for this purpose

Co-administered with local anesthetics
* Increases duration of action by decreasing local blood flow

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20
Q

Mechanism of action of norepinephrine

A

Similar to epinephrine:

  • Differs in receptor selectivity
  • Relatively little action on beta 2 receptors
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21
Q

Effect of norepinephrine on cardiovascular system.

BP / Heart / Vasculature

A

Blood pressure
* Increased systolic and diastolic pressure
- Initiates compensatory baroreflex response

Heart
* Decreased heart rate
- Increased vagal reflex activity
* Increased contractile force (inotropic)
- Unaffected by vagal reflex
* Cardiac output is unchanged or decreased

Vasculature
* Constriction of vascular beds
* Increased peripheral vascular
resistance

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22
Q

Adverse effects of norepinephrine

A

Some similarities with epinephrine but greater elevation in BP results in some unique adverse effects

  • Severe hypertension
  • Necrosis at injection site
    • Impaired circulation, with or without extravasation
    • Can be improved with infiltration of phentolamine (alpha receptor antagonist)
  • Peripheral vascular insufficiency
    • Reduced blood flow to organs (e.g. kidney, intestines)
23
Q

Therapeutic uses of norepinephrine

A
  • Raise or support blood pressure
  • Cardiogenic shock
    • Vasopressor of choice for initial management in patients
      with hemodynamic instability (systolic blood pressure
      <90 mm Hg or evidence of end organ hypoperfusion)
  • Septic shock
  • First-choice vasopressor for management of septic shock
  • Spinal anesthesia
24
Q

What is Dopamine and its mechanism of action

A
  • Metabolic precursor of NE and epinephrine
  • Central neurotransmitter
  • Particularly important in the regulation of movement

Mechanism of action
* Low concentrations: Agonist of D1 receptors
* High concentrations: Agonist of beta 1 and alpha 1 receptors

25
Q

Cardiovascular effects of dopamine

Low dose - receptor / medium dose - receptor / high dose - receptor

A

Low dose (D1 receptors)
* Vasodilation of renal, mesenteric, and coronary vasculature
(D1 receptors)
* Increases glomerular filtration rate, renal blood flow, and
natriuresis

Intermediate dose (beta 1)
* Increased heart rate and contractility
* Increased systolic pressure
* Little to no effect on diastolic pressure

High dose (alpha 1)
* Vasoconstriction and increased peripheral vascular resistance

26
Q

Adverse effects of dopamine

minor / serious

A

Some overlap with epinephrine

Minor
* Anxiety, headache, palpitations

Serious
* Angina pectoris
* Arrhythmias
- May cause increases in heart rate, increasing the risk of
tachycardia and other tachyarrhythmias including ventricular
arrhythmias

27
Q

Dopamine: Therapeutic uses

A

Severe decompensated heart failure
* Inotropic support

Cardiogenic shock
* Norepinephrine is preferred over dopamine for most
etiologies - lower likelihood for causing arrhythmias
* cardiogenic shock associated with bradycardia or aortic regurgitation, then dopamine is preferred

Sepsis and septic shock
* An alternative vasopressor to norepinephrine only in highly
selected patients

28
Q

2 nonselective beta agonists

A
  • Isoproterenol (Isuprel)
  • Dobutamine
29
Q

One Beta 2-selective agonist
(short-acting)

A

Albuterol

30
Q

Two Beta 2-selective agonists
(long-acting)

A

Salmeterol
Formoterol

31
Q

One Beta 3-selective agonist

A

Mirabegron

32
Q

Isoproterenol mechanism of action

A
  • Potent, nonselective beta agonist
  • Very low affinity for alpha receptors
33
Q

Isoproterenol: Cardiovascular and Respiratory effects

BP / Heart / Vasculature / Respiratory

A

Cardiovascular:
Blood pressure
* Decrease in diastolic pressure
* Systolic pressure may remain
unchanged or increase
* Typically, MAP will decrease

Heart
* Increase heart rate, contractile force,
and cardiac output

Vasculature
* Decreased peripheral resistance
* Primarily in skeletal muscle
vasculatur

Respiratory: Bronchodilation

34
Q

Isoproterenol: Adverse effects

A
  • Palpitations
  • Tachycardia
  • Headache
  • Flushing
  • Cardiac ischemia and arrhythmias: More common in patients with underlying coronary artery disease
35
Q

Isoproterenol: Therapeutic uses

A
  • Emergency stimulation of heart rate
  • Patients with bradycardia or heart block
  • NOTE: The use of isoproterenol in advanced cardiac life support (ACLS) has largely been supplanted by the use of other adrenergic agents (e.g. epinephrine and dopamine)
36
Q

Dobutamine Mechanism

A

Two enantiomers
* (-) isomer is an alpha 1 agonist
* (+) isomer is an alpha 1 antagonist

  • Both are agonists of beta receptors
    • (+) isomer has 10-fold more beta activity than (-) isomer

Racemic mixture is used clinically: Net effect is a beta agonist

37
Q

Dobutamine: Cardiovascular effects

BP / Heart / Vasculature

A

Blood pressure
* Minor effect on blood pressure

Heart
* Increases contractility and cardiac output
* Modest effect on heart rate
* More prominent inotropic effect than chronotropic

Vasculature
* Minimal effect on peripheral resistance
- Counterbalancing of:
– Alpha 1 receptor-mediated
vasoconstriction
– Beta 2 receptor-mediated
vasodilation

38
Q

Dobutamine Adverse Effects

BP / AFIB

A

Blood pressure and heart rate may increase significantly
* Requiring reduction of infusion rate
* Hypertensive patients may have an exaggerated pressor response

Patients with atrial fibrillation are at risk of marked
increases in ventricular response rates (ventricular
tachycardia)
* Due to facilitation of AV conduction
* May require digoxin or other agent as a preventative

39
Q

Dobutamine:
Therapeutic uses

A

Short-term management of patients with cardiac decompensation
* After cardiac surgery
* Congestive heart failure
* Acute myocardial infarction

40
Q

Beta 2-selective adrenergic
receptor agonists:
Mechanism of action
(Systemic conc? / heart effects)

A

Selective agonist of beta 2 receptors
* Not absolute
* Selectivity is lost at high concentrations
* Developed for the treatment of asthma and COPD
- Avoids adverse effects in the heart (beta 1)
- Administered by inhalation
– Targeted delivery to pulmonary tissue
– Very low systemic drug concentrations

  • Pulmonary effects:
  • Bronchodilation
  • Reduced airway inflammation: Suppression of leukotriene and histamine release from mast cells
41
Q

Beta 2-selective adrenergic
receptor agonists:
Adverse effects

A
  • Tremor: Tolerance generally develops
  • Anxiety
  • Tachycardia
  • Arrhythmias, myocardial ischemia: Rare in patients without cardiac disease
  • Greater risk in patients with underlying coronary artery disease or preexisting arrhythmia
  • Increased in patients receiving MAO inhibitors

Note: Likelihood of adverse effects can be greatly reduced by
inhalational administration

42
Q

Short-acting beta 2-selective agonists: Albuterol: Pharmacokinetics and Therapeutic use

A

Pharmacokinetics
* Duration of action: 3-6 hours (inhaled)
* Onset of action: Bronchodilation within 15 min

Therapeutic use
* Asthma: Symptomatic relief of
bronchospasm

43
Q

Pharmacokinetics and Therapeutic uses of Long-acting beta 2-selective agonists: Salmeterol, Formoterol

A

Pharmacokinetics
* Duration of action: >12 hours (inhaled)

Onset of action
* Salmeterol: Relatively slow
- Not suitable for treatment of acute asthma symptoms
* Formoterol
- Bronchodilation within minutes

Therapeutic use
* Chronic obstructive pulmonary disease (COPD)
* Asthma
- Nocturnal and persistent

44
Q

Mirabegron: Type of receptors and where are they expressed, mechanism of action, adverse effects and therapeutic use

A
  • Beta 3 receptors are expressed in
    brown fat, GI, and bladder

Mechanism of action
* Relaxation of the detrusor muscle of
the bladder
- Increased bladder capacity

Adverse effects
* Hypertension (9-11%)
* Urinary tract infections (3-6%)
* Headache (2-4%)

Therapeutic use
* Urinary incontinence

45
Q

Mechanism of action of Phenylephrine

A

Mechanism of action
* Potent, direct-acting alpha 1 adrenergic agonist
* Virtually no beta-adrenergic activity
* Direct acting vasoconstrictor

46
Q

Cardiovascular effects of Phenylephrine

BP / Heart / Vasculature

A

Blood Pressure
* Increases systolic and diastolic pressure

Heart
* Decreased heart rate: Due to reflex bradycardia

Vasculature
* Vasoconstriction
* Decreased blood flow

47
Q

Therapeutic uses of Phenylephrine

A

Hypotension
* Orthostatic hypotension (Midodrine)
* Shock

Nasal decongestant

Ophthalmic: Mydriatic agent

48
Q

What reflex blunts the alpha-1 agonist blood pressure effect

A

Compensatory autonomic baroreflex response

49
Q

Pseudoephedrine: Mechanism of action and Therapeutic use

A

Mechanism of Action: Mixed acting sympathomimetic like ephedrine

However, receptor selectivity differs from ephedrine
* Direct alpha 1 agonist
- Little direct beta 2 agonist activity

Therapeutic use
* Nasal decongestant

50
Q

Amphetamine Mechanism of Action

A
  • Powerful CNS stimulant with peripheral sympathomimetic actions

Mechanism of action
* Releases biogenic amines from storage vesicles in CNS and peripheral sympathetic nerve terminals
- Inhibits vesicular monoamine transporter (VMAT)

51
Q

Amphetamine: Cardiovascular, smooth muscle and CNS effects

A

Cardiovascular effects
* Increases systolic and diastolic pressure
* Heart rate is often reflexively slowed

Other smooth muscle effects
* Contraction of the urinary sphincter
* GI effects are unpredictable

CNS effects
* One of the most potent sympathomimetic amines in stimulating the CNS
* CNS effects will be discussed in
future lectures

52
Q

Amphetamine: Therapeutic use

A

Used for the treatment of:
* Narcolepsy
* ADHD

53
Q

Dextroamphetamine: Mechanism of action and therapeutic uses

A
  • Same as amphetamine except greater CNS and less peripheral
    action
  • Same therapeutic uses as amphetamine
54
Q

Methylphenidate: Mechanims of Action and Therapeutic Uses

A
  • Piperidine derivative, structurally similar to amphetamine
  • Mild CNS stimulant
  • More prominent effects on mental than on motor activities

Therapeutic use:
Both methamphetamine and methylphenidate are approved for the treatment of narcolepsy and ADHD

Note: Amphetamine, methamphetamine, and methylphenidate are Schedule II drugs due to a high potential for abuse

MWU Pharmacology I (9 decks)

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