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IC > Adrenergic Pharmacology I > Flashcards

Adrenergic Pharmacology I Flashcards

1
Q

Adrenoreceptor activating and other sympathomimetic drugs

A

drugs that mimic Epi or NE are sympathomimetic

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2
Q

SNS regulates

A

heart and peripheral vasculature

  • especially in response to stress
  • SNS stimulation mediated by release of NE
  • NE and Epi (from adrenal medulla) activate adrenoreceptors
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3
Q

Direct acting agents

A

norepinephrine, epinephrin

-stimulate adrenoreceptors

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4
Q

Indirect acting agents

A

promote release of endogenous catecholamines

  • displace stored catecholamines (amphetamine, tyramine)
  • inhibit reuptake of catecholamines (cocaine)
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5
Q

alpha1 adrenoreceptors

A
  • contraction of smooth muscle in peripheral vasculature- contraction of smooth muscle–> increased BP by increasing resistance
  • PLC activation, stimulating polyphosphoinosotide hydrolysis, formation of IP3 and DAG
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6
Q

alpha2 adrenoreceptors

A
  • most commonly found in NE releasing sympathetic post ganglionic neurons
  • presynaptic autoregulation of neurotransmitter release
  • inhibit adenylyl cyclase, decrease intracellular cAMP, decreases Ca so decreases ability to release catecholamines
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7
Q

beta 1 receptors

A

approximately equal affinity for Epi and NE

-heart

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8
Q

beta 2 receptors

A

higher affinity for Epi than NE

-smooth muscle relaxation

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9
Q

beta adrenoreceptors

A
  • subtypes defined by affinity for Epi and NE
  • found in vasculature, lung, eye and most other end organs
  • activate adenylyl cyclase, increasing cAMP levels
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10
Q

Dopamine receptors

A

Also adrenergic receptors

  • very important in brain and also splanchnic and renal vasculature
  • D1 stimulates, D2 inhibits adenylyl cyclase
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11
Q

receptor responsiveness of adrenoreceptors

A

can have desensitization or denervation supersensitivity

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12
Q

Phenylethylamine

A
  • parent compound (benzene ring with ethylamine side chain)
  • when combined with a catechol (benzene ring with two hydroxyl groups) leads to dopamine (epinephrine and NE are modifications of dopamine)
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13
Q

Effect on CV

A

Affects blood vessels

  • Alpha receptors increase arterial resistance (inc blood pressure)
  • Beta2 receptors relax vascular smooth muscle (on some vascular beds to oppose contraction to increase capacitance)
  • Skin and splanchnic vessel- predominantly alpha receptors (pure increase in resistance, ppl will turn white because of low blood flow to skin)
  • Skeletal muscles- more beta2 receptors (not as much contraction, passive shift of blood flow and more blood goes to skeletal muscles than skin and viscera)
  • renin secretion stimulated by beta1
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14
Q

Effect on Heart

A

Beta1 receptor activity dominates

  • Opposing parsympathetic effects of vagus nerve, which is tonically active in heart
  • Activation results in increased calcium influx in cardiac cells- positive inotrophy and chronotrophy
  • AV conduction velocity increases, refractory period decreased
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15
Q

Effect on eye

A
  • Alpha agonists- contract radial pupillary dilator muscle, which causes mydriasis; can slightly increase drainage of aqueous humor
  • beta agonists- increase aqueous humor secretion (ciliary epithelium)- antagonists important in tx of glaucoma (esp open angle)
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16
Q

respiratory tract

A
  • Beta2 receptors relax bronchial smooth muscle and increase airflow through lungs (rescue inhalers)
  • alpha1 receptors in upper resp mucosa contraction produces decongestion
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17
Q

GI tract

A
  • beta receptors on smooth muscles mediate relaxation

- alpha2 receptors on myenteric plexus- remove PNS tone

18
Q

GU tract

A

alpha1- contract bladder base, urethral sphincter–> urinary retention

beta2 of bladder wall- relax smooth muscle–> urinary retention

19
Q

Exocrine glands

A

alpha1 receptors on apocrine (stress glands)- sweating on palms, brow, upper lip

20
Q

Metabolic effects

A
  • SNS activity shift toward energy liberation and usage
  • Beta3 receptor- inc lipolysis, enhances glycogenolysis, glucose relase, inc insulin secretion
  • alpha2 receptor activation decreases insulin release
21
Q

Epinephrine (adrenaline)

A
  • potent vasoconstrictor (alpha1) and cardiac stimulant (beta1)
  • pos inotropic and chronotropic actions on heart
  • activates beta2 receptors
  • mixed TPR, in some vessels inc venous capacitance (skeletal muscle)
22
Q

Norepinephrine (noradrenaline)

A

Similar to epi on alpha1 receptors on heart

  • similar potency at beta1
  • little effect on beta2
  • inc peripheral resistance
  • inc both diastolic and systolic blood pressure
  • compensatory vagal reflexes may lower heart rate but at high doses will directly increase heart rate
  • alpha1, alpha2, beta1
23
Q

Isoproterenol

A
  • synthetic drug
  • nonselective beta-receptor agonist (no alpha effects)
  • positive chronotropic and inotropic actions
  • inc cardiac output
  • decrease both diastolic and MAP
  • beta1, beta2
24
Q

Dopamine

A
  • endogenous catecholamines

- D1 receptors imp in renal vasculature

25
Q

Dobutamine

A
  • synthetic
  • relatively beta1-selective and alpha1 selective
  • inc MAP, PR, stimulates heart
26
Q

Phenylephrine

A

-prototypic alpha1 agonist
-not a catechol derivative
not inactivated by COMT
-longer DOA than catecholamines
-nasal decongestant and cause mydriasis, can raise bp via alpha1 effect

27
Q

Methoxamine

A

alpha1 selective

28
Q

Ephedrine

A

First orally active sympathomimetic drug

29
Q

Pseudoephedrine

A
  • widely available OTC decongestant

- indirect effects of releasing endogenous NE

30
Q

Oxymetazoline, xylometazoline

A

direct alpha1 agonists

  • topical decongestants
  • can lead to desensitization of the alpha1 receptors
31
Q

Alpha2 selective agonists

A
  • clonidine, methyldopa, guanfacine, guanabenz
  • coupling of alpha2 receptors- (negative coupling) autoreceptor regulation of norepinephrine release
  • decrease endogenoush catecholamine release
  • Used as antihypertensives
  • diminish SNS outflow
  • can lead to orthostatic hypotension
32
Q

Beta1 selective agonists

A
  • dobutamine (also has alpha1 activity)
  • Prenalterol- partial agonist
  • Increase CO with less reflex tachycardia
  • lack of beta2 stimulated venous dilation
33
Q

Beta2 selective agonists

A
  • albuterol, salmeterol, terbutaline, ritodrine, imp place in treatment of asthma
  • uterine relaxation in premature labor (ritodrine)
34
Q

Indirect sympathomimetics

A

amphetamines, methamphetamine, methylphenidate, cocaine, tyramine, ephedrine/pseudoephedrine (also direct)

35
Q

Amphetamine

A

indirect sympathomimetic

  • amplifies amt of NE released from adrenergic neuron terminal into synapse
  • can inhibits or reverses activity of uptake1
  • marked stimulant effects on mood and alertness, depressant effect on appetite, common drug of abuse
36
Q

methamphetamine

A

similar to amphetamines, with higher CNS effect

37
Q

Methylphenidate

A

amphetamine variant, used in ADHD

38
Q

Cocaine

A
  • local anesthetic

- sympathomimetic due to blockade of uptake1

39
Q

Tyramine

A
  • releases stored catecholamines
  • found in high concentrations in fermented foods such as cheese
  • MAO inhibitors potentiate effects
  • can produce hypertensive crisis
40
Q

Sympathomimetics- clinical applications

A
  • conditions in which blood flow or pressure is to be enhanced (hypotension, hypovolemic or cardiogenic shock, cardiac insufficiency)
  • conditions in which blood flow is to be reduced (local anesthetic will include epinephrine to contract vascular smooth muscle to reduce blood flow in that area so it isn’t washed away, reducing mucous congestion, heart block, cardiac arrest)
  • heart failure (dobutamine, desensitization limits)
  • bronchial asthma (bronchodilation by beta2)
  • anaphylaxis
  • fundoscopic examination of retina- alpha1 mydriasis
  • premature labor (uterus relaxed by beta2 agonist)
  • narcolepsy- amphetamines produce alertness
41
Q

toxicity

A

related to extension of pharmacologic effects in CV and CNS

-htn, tachycardia, CNS- restlessness, tremor, insomnia, anxiety

IC (31 decks)

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