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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
Cardiovascular effects of dopamine | Low dose - receptor / medium dose - receptor / high dose - receptor
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
Adverse effects of dopamine | minor / serious
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
Dopamine: Therapeutic uses
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
2 nonselective beta agonists
* Isoproterenol (Isuprel) * Dobutamine
29
One Beta 2-selective agonist (short-acting)
Albuterol
30
Two Beta 2-selective agonists (long-acting)
Salmeterol Formoterol
31
One Beta 3-selective agonist
Mirabegron
32
Isoproterenol mechanism of action
* Potent, nonselective beta agonist * Very low affinity for alpha receptors
33
Isoproterenol: Cardiovascular and Respiratory effects | BP / Heart / Vasculature / Respiratory
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
Isoproterenol: Adverse effects
* Palpitations * Tachycardia * Headache * Flushing * Cardiac ischemia and arrhythmias: More common in patients with underlying coronary artery disease
35
Isoproterenol: Therapeutic uses
* 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
Dobutamine Mechanism
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
Dobutamine: Cardiovascular effects | BP / Heart / Vasculature
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
Dobutamine Adverse Effects | BP / AFIB
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
Dobutamine: Therapeutic uses
Short-term management of patients with cardiac decompensation * After cardiac surgery * Congestive heart failure * Acute myocardial infarction
40
Beta 2-selective adrenergic receptor agonists: Mechanism of action (Systemic conc? / heart effects)
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
Beta 2-selective adrenergic receptor agonists: Adverse effects
* 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
Short-acting beta 2-selective agonists: Albuterol: Pharmacokinetics and Therapeutic use
Pharmacokinetics * Duration of action: 3-6 hours (inhaled) * Onset of action: Bronchodilation within 15 min Therapeutic use * Asthma: Symptomatic relief of bronchospasm
43
Pharmacokinetics and Therapeutic uses of Long-acting beta 2-selective agonists: Salmeterol, Formoterol
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
Mirabegron: Type of receptors and where are they expressed, mechanism of action, adverse effects and therapeutic use
* 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
Mechanism of action of Phenylephrine
Mechanism of action * Potent, direct-acting alpha 1 adrenergic agonist * Virtually no beta-adrenergic activity * Direct acting vasoconstrictor
46
Cardiovascular effects of Phenylephrine | BP / Heart / Vasculature
Blood Pressure * Increases systolic and diastolic pressure Heart * Decreased heart rate: Due to reflex bradycardia Vasculature * Vasoconstriction * Decreased blood flow
47
Therapeutic uses of Phenylephrine
Hypotension * Orthostatic hypotension (Midodrine) * Shock Nasal decongestant Ophthalmic: Mydriatic agent
48
What reflex blunts the alpha-1 agonist blood pressure effect
Compensatory autonomic baroreflex response
49
Pseudoephedrine: Mechanism of action and Therapeutic use
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
Amphetamine Mechanism of Action
* 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
Amphetamine: Cardiovascular, smooth muscle and CNS effects
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
Amphetamine: Therapeutic use
Used for the treatment of: * Narcolepsy * ADHD
53
Dextroamphetamine: Mechanism of action and therapeutic uses
* Same as amphetamine except greater CNS and less peripheral action * Same therapeutic uses as amphetamine
54
Methylphenidate: Mechanims of Action and Therapeutic Uses
* 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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