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Pharmacology > Adrebergic System > Flashcards

Adrebergic System Flashcards

1
Q

Possibilities to influence the adrenergic system

A

Presynaptic stimulation
Postsynaptic stimulation
= sympathomimetics

Presynaptic inhibition
Poststnaptic inhibition
= sympatholytics

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2
Q

Presynaptic stimulation

A
  1. synthesis:
    - precursor substance = levodopa
  2. release:
    - depolarization = 4-aminopyridine/fampiridin
    K+ channel blocker
    - increased ca2+ concentration
    - latrotoxin - explosive release of NE
  3. Presynaptic receptors
    - activation of presynaptic stimulatory b2 receptors
    - inhibition of presynaptic inhibitory a2 receptors (yohimbine, mianserine)
    - activation of presynaptic stimulatory hereroreceptors (AT1)
  4. Indirectly acting sympathomimetics
    - thyramine, ephedrine, ampthanine, they promote transmitter release
  5. Reuptake inhibitors
    - cocaine, tricyclic antidepressants (amitryptyline, desipramine)
  6. MAO inhibitors
    - tranylcypromine, selegiline, moclobemid
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3
Q

Postsynaptic stimulation groups

A

Direct acting sympathomimetics

  • catecholamines
  • b1 receptor agonist
  • b2 receptor agonist
  • a1 receptor agonist

Indirectly acting sympathomimetics

  • tyramine
  • ephedrine
  • amphetamine
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4
Q

Catecholamines

A

Direct acting sympathomimetics

```
Epinephrine/adrenaline
Norepinephrine/noradrenaline
Isoprenaline
Dopamine
Dobutamine and dopexanine
~~~

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5
Q

Epinephrine/adrenaline

A

Direct acting sympathomimetics
- activate all adrenergic receptors
- vasodilation = b2
- vasoconstriction = a1
— determined by receptor distribution (MAP IS NOT CHANGED)
- positive inotropic and chromotropic actions on the heart
- bronchodilation
- indication; anaphylactic shock, emergency heart block and cardiac arrest, asthmatic state, inhaled E for croup/subglottic laryngitis, reduction of regional blood flows

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6
Q

Norepinephrine/noradrenaline

A

Direct acting sympathomimetics

  • activates a and b1 receptors, but little effect on b2
  • vasoconstriction and increased BP
  • Compensatory vagal reflexes can overcome its direct positive chronitropic effect on heart
  • indication: neurogenic shock, septic shock, cardiogeic shock and locally to reduce blood flow
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7
Q

Isoprenaline

A

Direct acting sympathomimetics

  • potent and selective b receptor agonist
  • positive inotropic and chronitropic action on heart
  • vasodilation, decreased diastolic pressure, and decreased MAP
  • bronchodilation
  • indication: bradycardia and AV blocks
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8
Q

Dopamine

A

Direct acting sympathomimetics

  • low dose: d1 receptor
  • medium dose: b1 receptor
  • high dose: a receptor (act as e)
    Indication: cardiogenic shock (low to medium dose).
    Adverse effects: tachycardia, tolerance,
  • bad pharmacokinetics
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9
Q

Selective b1 receptor agonist

A

Dopamine in medium dose
Dobutamine
Ibopamine
Prenalterol

Indication: cardiogenic shock, limited use in CHF

Adverse effects: tachycardia

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10
Q

Peripheral D receptor agonists

A
  • Dopamine in low dose: dilation of mesenteric and renal blood vessels
  • fenoldopam: peripheral vasodilation in mesenteric vascular bed, for severe hypertension
  • dopexamine: D, B2, (b1) agonist, reuptake inhibitor
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11
Q

Selective b2 receptor agonist

A

Main action and indication
- bronchodilation (COPD, asthma)
—SABA; salbutamol, terbutaline, fenoterol, levosalbutamol
—LABA; salmeterol, formoterol, clenbuterol, bambuterol, procaterol, indacaterol, clodaterol, vilanterol

  • relaxation of pregnant uterus
    — terbutaline, ritodrine

Potential adverse effects
- tremor, tachycardia, hyperglycemia, hypokalemia

No absolute specificity - if possible= topical use

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12
Q

Alpha receptor agonists

- local and systemic use

A

1.Local use - nasal decongestant; activates a1 and a2
- naphazolin, xylometazolin, oxymetazoline, phenylephrin
— vasoconstriction locally
— side effects: rebound hyperemia, ischemic changes of mucous membranes

  1. Local use - ophthalmologic use
    - decongesion - phenylephrin
    - myadriasis - phenylephrin
    - glaucoma - apraclonidine, brimonidine a1
  2. Systemic use
    - selectivity is extremely important
    - a1 selective agonist = sympathomimetics
    —vasoconstriction and increased BP
    —phenylephrin, midodrine, methoxamine
    - a2 selective agonist = sympatholytic
    — due to enhanced negative feedback
    — decreased BP (transient increase)
    — clonidine, guanfacin
    — used as antihypertensive agents
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13
Q

Indirectly acting sympathomimetics

A

They release NE from nerve terminals, rapid development of tolerance

  • tyramine
  • ephedrine
  • amphetamine
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14
Q

Tyramine

A

Indirect acting sympathomimetics

  • not used as therapeutic agent
  • found in cheese, chicken liver, red wine
  • metabolized by MAO-a in GI tract and inactivated
  • if treated with MAO-a inhibitors= avoid food with tyramine - can cause hypertensive crisis
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15
Q

Ephedrine

A

Indirect acting sympathomimetics

  • alkaloid
  • high oral bioavailability,
  • long action of duration
  • penetrate bbb, mild stimulant
  • mixed sympathomimetic mechanism of action: weak receptor activator and release NE
  • vasoconstrictor or bronchodilator when weak and prolonged action is needed
  • enantiomer- pseudoephedrine= over the counter drug
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16
Q

Amphetamine

A

Indirect acting sympathomimetics
- orally active compound with long duration
- enters CNS easily and release biological amines and cause a marked stimulant effect on mood and alertness
- euphoria =abuse
- decreased appetite
- periphery= indirectly acting sympathomimetic
- related drugs;
— methylpheridate - ADHD
— MDMA
— methamphetanine

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17
Q

Reuptake inhibitors

A

Cocaine
TCA and related compound
SNRI, SSNRI

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18
Q

Cocaine

A

Reuptake inhibitor

  • LA
  • block NE and D reuptake on periphery and CNS
  • sympathomimetics
  • euphoria = abuse
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19
Q

TCA and related compounds

A

Reuptake inhibitors

  • desipramadine, amitriptyline
  • used to treat mental depression
  • block NE reuptake in PNS + CNS
  • a and m blockade may complicate their autonomic action - risk of adverse cardinal effects
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20
Q

SNRI, SSNRI

A

Reuptake inhibitors
- serotinin NE reuptake inhibitors and selective serotonin ne reuptake inhibitors
—reboxetine, venlafaxine
— antidepressant, no receptor blockade

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21
Q

MAO Inhibitors

A

Irreversible, non-selective

  • tranylcypromine, parglycine
  • antidepressants- not used due to severe side effects

Reversible mao-a inhibitors

  • modobemid
  • treat mental depression

Irreversible mao-b inhibitors

  • selegiline
  • Parkinson’s
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22
Q

Presynaptic inhibition = sympatholytics

A
  1. A-methyltyrosine/methyrosine
    - blocks tyrosine hydroxylase enzyme
  2. Reserpine
    - prevents transmitter release
  3. tetrodotoxin, saxitoxin
    - LA
    - prevent/block VGSC
  4. Omega-conotixin
    - block ca2+ channels
  5. Activation of inhibitory presynaptic a2 autoreceptors
    - clonidine, methyldopa
  6. Activation of presynaptic inhibitory heteroreceptors
    - m2, d2, h3, etc
  7. Adrenergic neuron blockers
    - guanethidin and bretylium
    - inhibit transmission release
  8. 6-OH-dopamine
    - destroy the nerve terminal
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23
Q

Postsynaptic inhibition

Groups

A

Decrease sympathetic activity

  1. Beta-blockers
    - non-selective
    - cardioselective/b1 selective
  2. A1 antagonist
    - selective a1 antagonist
    - non-selective a antagonist
  3. A2 receptor agonist
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24
Q

Non-selective beta blockers

A 
Propranolol 
Pindolol 
Timolol
Sotalol (also: k+ channel blocker)
Carvediol (also: a1 blocker)
Labetalol (also: a1 blocker)
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25
Q

B1 selective/cardioselective beta blockers

A 
Atenolol
Metoprolol
Bisoprolol
Esmolol
Celiprolol
Betaxolol
Nebivolol
Acebutolol
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26
Q

Partial agonistic activity of beta blockers = ISA

intrinsic sympathomimetic activity

A 
Pindolol
Acebutolol
Oxprenolol
Alprenolol
Celiprolol- bronchoconstriction

ISA at b2 receptors

Less likely with decreased HR and lipid abnormalities in plasma

27
Q

Consequence of beta blocking

A
  • negative chronotropic and inotropic actions on heart
  • decreases BP (in part due to less renin release) - b1
  • bronchoconstriction - b2
  • local vasoconstriction - b2
  • decreased production of aqueous humor
  • impaired recovery from hypoglycemia - b2
  • increased VLDL and decreased HDL
28
Q

Indication of beta blockers

A 
Hypertension 
Angina pectoris 
Supraventricular tachyarrhythmias
CHF
after AMI
Hypertrophic obstructive cardiomyopathy 
Hyperthyroidism
Pheochromocytoma
Portal hypertension 
Esophageal varicose 
Glaucoma 
Performance anxiety 
Migraine 
Essential tremor 
Proliferating hemangioma (newborn)
29
Q

Adverse effect of beta blockers

A 
Bronchoconstriction 
Cardiac decompensation
Bradycardia 
Decreased AV conduction 
Cold extremities 
Worsening peripheral vascular disease 
Uterus contraction in pregnancy 
Hypoglycemia 
Hyperlipidemia 
Increased potassium levels 
Sleep disturbance 
Depression

Abrupt discontinuation can give increased risk of ischemic heart disease

30
Q

Lipid solubility of beta blockers

A

High lipid solubility:

  • propranolol
  • nebivolol

Low lipid solubility

  • atenolol
  • sotalol
  • acebutolol
31
Q

Action of beta blockers on ion channels

A

Weak LA effect (Na+ channel block):

  • propranolol
  • pindolol
  • metoprolol
  • acebutolol

Block k+ channel
- sotalol - antiarrhythmic drug (I and II)

32
Q

Beta blockers with additional vasodilator effect (3rd gen)

A

Block of a1

  • labetalol
  • carvediol

NO- mediated relaxation

  • nebivolol
  • antihypertensive indication
33
Q

Half-life beta blockers

A 
Ultra-short acting 
1. esmolol
— b1 selective 
— 10 min half life 
— critically ill patients

Long half life

  1. Nadolol - 16-20h
  2. Betaxolol- 14-20h
  3. Bisoprolol- 10-12 h
  4. Nebivolol - 10 h
34
Q

Alpha receptor antagonists

A
  • selective a1 receptor antagonist
  • non-selective a receptor antagonist
    — synthetic compound: phenoxybenzamine and phentoamine, (tolazoline)
    — ergot alkaloids
35
Q

Therapeutic interest of a receptor antagonist

A

Smooth muscle relaxation
Antihypertensive action
Peripheral vascular disease
Benign prostate hyperplasia

Selective a1 antagonists cause less tachycardia than the non-selective ones.

36
Q

A2 receptor agonist

A

Sympatholytic effects due to negative feedback on autoreceptor

  • clonidine
  • guanabenz
  • Guanfacine
  • moxinidine
  • rilmenidine
  • methyldopa
  • dexamedetomidine - sedation
  • tizanidine - centrally acting muscle relax
  • apraclonidine, brimonidine - glaucoma
37
Q

Clonidine

A

A2 receptor agonist

  • Sympatholytic effects due to negative feedback on autoreceptor
  • imidazoline derivative
  • moa: enhances negative feedback on presynaptic a2 autoreceptors, stimulates postsynaptic a2 receptors in medulla (BP regulation) and stimulates imidazoline 1 receptors in the medulla.
  • indication: HT (acute, mild to moderate), alcohol and opioid withdrawal, peri anesthetic medication, sedation and analgesia in ICU, diarrhea in DM, ADHD, glaucoma

Adverse effects; sedation, dry mouth, bradycardia, orthostatic hypotension, mental depression.

Abrupt withdrawal can cause HT crisis and increased sympathetic activity

38
Q

Guanabenz and guanfacine

A

A2 receptor agonist

  • Sympatholytic effects due to negative feedback on autoreceptor
  • centrally acting antihypertensive drugs
  • clonidine like action but different structure
39
Q

Moxonidine and rilmenidine

A

A2 receptor agonist

  • Sympatholytic effects due to negative feedback on autoreceptor
  • newer imidazoline derivatives with clonidine like structure
  • more sensitive to imidazoline receptor 1 in adrenal medulla
  • less affinity to a2?
  • indication: HT
  • sedation and dry mouth occurs less frequently than with clonidine
40
Q

Methyldopa

A

A2 receptor agonist

  • Sympatholytic effects due to negative feedback on autoreceptor
  • false substrate is FOPA-decarboxylase
  • methylNE= a2 agonist
  • slow onset of action
  • indication: mild to moderate HT, and HT in pregnancy
  • adverse effects: sedation, dry mouth, hyperprolactinenia, extrapyrimidal symptoms, depression, +Coombs test, immune hemolysis, liver toxicity
41
Q

Selective a1 receptor antagonists

A 
Prazosin
Terazosin
Doxazosin
Alfuzosin
Tamsulozin
Silodosin
Urapidil
Labetalol
Carvediol
42
Q

Non-selective alpha blockers

A

Phenoxybenzamine
Phentolamine
Tolazoline

43
Q

Prazosin

A

Selective a1 receptor antagonist

Indication: chronic treatment of mild to moderate HT, and BPH

  • orally active
  • short half life: 3x/day
  • side effects; first dose phenomenon (HT and syncope) - start treatment at bed time to avoid, mild and non-spesific: dizziness, palpitations
44
Q

Terazosin and dixazosin

A

Selective a1 receptor antagonist

  • prazosin like with longer half life
  • indication; HT and BPH
45
Q

Alfuzosin, tamsulosin, and silodosin

A

Selective a1 receptor antagonist

  • urinary tract
  • BPH
46
Q

Urapidil

A

Selective a1 receptor antagonist

  • weak a2 agonist, 5-HT1a agonist, and beta antagonistic action
  • hypertensive crisis
47
Q

Labetalol and carvediol

A

Selective a1 receptor antagonist.

Also beta antagonist

48
Q

Phenoxybenzamine

A

Non-selective synthetic alpha blocker

  • irreversible a blocker, long duration (14-18h)
  • indication: pheochromocytoma
49
Q

Phentolamine and tolazoline

A

Non-selective synthetic alpha blockers

  • reversible a blocker
  • strong
  • pheochromocytoma (diagnosis and treat)

Tolazoline - weak, vasodilation

50
Q

Ergot alkaloids groups

A
  • produced by fungus: claviceps purpurea
  • lysergic acid derivatives (LSD)
  • 2 major families of natural compounds
    1. Amine alkaloids
  • ergometrine
    2. Peptide alkaloids
  • ergotamine
  • ergocryptine
  • ergocrystine
  • ergocornine

Agonist, partial agonist or antagonist action on several receptors, especially a and 5-HT and D

51
Q

Main effect of ergot alkaloids

A

Vasoconstriction
Vasospasm

Powerful stimulation of pregnant uterus

CNS action

52
Q

Structurally related drugs if ergot alkaloids

A

Dihydro-derivatives: more selective for a receptors (antagonist)

Methysergid: more selective for 5-HT receptor (antagonist)

Bromocryptine, cabergoline; more selective for D receptors (agonist)

Lysergic acid diethylamine(LSD); peripheral agonist on5-HT in CNS

53
Q

Therapeutic indication of ergot alkaloids

A

Postpartum hemorrhage

  • ergometrine, ergotamine
  • never before delivery

Migraine
- ergotamine

54
Q

Therapeutic indication of ergot derivatives

A

Hyperprolactinemia

  • bromocryptine
  • cabergoline

Parkinson’s
- bromocryptine, cabergoline

Migraine
- dihydro ergotamine

Peripheral vascular disease
- dihydro- derivatives

55
Q

Side effects of ergot alkaloids

A 
Nausea
Vomiting 
Diarrhea
Prolonged vasospasm
CNS disturbances
56
Q

Drugs with alpha blocking side effects

A
  1. Several (mostly tricyclic) antidepressants
    - amitriptyline
    - imipramine
  2. Several antipsychotics
    - phenothiazines
    - chlorpromazine
    May cause HT and reflex tachycardia
  3. Quinidine
    - antiarrhythmic drug
    - to rapid iv infusion may cause BP fall
57
Q

Adrenergic neuron blockers

A 
Quanethidine
Debrisoquine
Bretylium
Reserpine
Tetrabenazine
Methyltyrosine
58
Q

Quanethidine and debrisoquine

A
  • adrenergic neuron blockers
  • inhibit NE release from synaptic nerve terminals
  • antihypertensive indication
  • adverse effects; postural HT, diarrhea, impaired ejaculation, sodium and water retention, nasal stiffness
59
Q

Bretylium

A
  • adrenergic neuron blockers
  • inhibit release of ne from synaptic nerve terminals
  • blocks potassium channels on the heart - antiarrhythmic indication
  • adverse effects: initial release of ne can precipitate arrhythmia, sympatholytic action
60
Q

Reserpine

A
  • adrenergic neuron blockers
  • blocks the uptake of biogenic amines into the synaptic vesicles, they are not stored in the vesicles, broken down by MAO
  • enters the brain - depletion of me, dopamine, serotonin in both several and peripheral neurons
  • theoretical indication; HT And psychosis
  • side effects: sympatholytic action, mental depression, Parkinsonism
61
Q

Tetrabenazine

A

Adrenergic neuron blockers

Huntington
Tourette

62
Q

Methyltyrosine

A

Block the norepinephrine synthesis

Adrenergic neuron blocker

63
Q

Chronic ergot poisoning

A 
Hallucinations 
Convulsions 
Prolonged vasospasm 
Gangrene 
Burning pain 
Abortion in pregnancy

Pharmacology (14 decks)

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