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Pharmacology > Sympathetic Neurotransmission and Adrenoceptor Agonists > Flashcards

Sympathetic Neurotransmission and Adrenoceptor Agonists Flashcards

1
Q

alpha1-adrenoceptor - MoA and Location

A

Phospholipase C activation, increased IP3 and release of Ca

Smooth muscle at sympathetic neuroeffector junctions, exocrine glands, CNS

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2
Q

alpha1-adrenoceptor - Effect

A

Smooth muscle contraction (vascular, iris dilator, bladder, urethra, prostate), exocrine gland secretion, neuronal excitation
–> Vasoconstriction increased BP

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3
Q

alpha2- adrenoceptor - MoA and Location

A

Inhibition of adenylyl cyclase and decreased cAMP

Distributed in presynaptic neurons, blood platelets, and tissues (ocular/adipose/intestinal/hepatic/renal/endocrine)

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4
Q

alpha2- adrenoceptor - Effect

A

Sympathetic postganglionic neurons: Autoreceptors, activation –> feedback inhibition of norepinephrine release from nerve terminals
Blood platelets: platelet aggregation
Pancreas: inh of insulin secretion
Eyes: decreased secretion of aqueous humor
CNS effects

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5
Q

Beta adrenoceptors - MoA

A

Adenylyl cyclase activation, increased cAMP, protein kinase A activation
–> phosphorylation of other proteins and enzymes.

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6
Q

Beta1- adrenoceptor - Effect

A

Cardiac stimulation:
Positive chronotropic (increased HR), inotropic (increased contractility), dromotropic (increased impulse conduction velocity).
Kidney:
Increased Renin secretion from juxtaglomerular cells.

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7
Q

Beta2- adrenoceptor - Effect

A

Smooth muscle:
Relaxation ( bronchi, uterus, vascular)
Skeletal muscle: potassium uptake
Liver: glycogenolysis

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8
Q

Beta3- adrenoceptor - Effect

A

Adipose: lipolysis
Skeletal muscle: thermogenesis
Smooth muscle: relaxation

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9
Q

D1 receptor - MoA

A

Increases cAMP by stimulating adenylyl cyclase. cAMP activates protein kinase A –> phosphorylation of other proteins and enzymes.

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10
Q

D1 receptor - Effect

A

Relaxation of vascular smooth muscle

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11
Q

D2 receptor - MoA

A

Decreases cAMP, increases K currents, decreases Ca influx

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12
Q

D2 receptor - Effect

A

Modulation of neurotransmission in the sympathetic and CNS

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13
Q

Imidazoline receptors - MoA and Location

A

Activated by adrenoceptor agonists that possess an imidazoline structure

CNS, peripheral tissues

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14
Q

Imidazoline receptors - Effect

A

Natriuresis and decrease of symp outflow from CNS

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15
Q

Catecholamines - Indications

A

Shock
Hypovolemic shock (inadequate blood V)
Cardiogenic shock (inadequate cardiac function)
Rogenic shock/Neurogenic
Septic shock (massive vasodilation secondary to production of toxins)
Anaphylactic shock (hypotension, difficulty breathing)

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16
Q

Catecholamines - Adverse effects

A

Excessive vasoconstriction –> tissue ischemia and necrosis.

Excessive doses: reduce blood flow to vital organs such as kidneys or cause excessive cardiac stimulation –>
Tachycardia
Arrhythmias

Beta adrenoceptor agonists can cause:
hyperglycemia, esp diabetes patients.

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17
Q

Direct acting catecholamines

A 
Dobutamine
Dopamine (both)
Epinephrine
Norepinephrine
Isoproterenol
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18
Q

Norepinephrine - MoA and Effects

A

Vasoconstriction and increased BP (alpha1)

Greater affinity for beta1 adrencoceptors then for beta2. –> constricts all blood vessels

Cardiovascular effect: primarly results from activation of alpha1 adrenoceptors. Leads to vasoconstriction and increases peripheral resistance, which in turn increases the systolic and diastolic blood pressure.

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19
Q

Norepinephrine - Indication

A

Hypotension
Septic shock
Cardiogenic shock when response to dopamine is inadequate or tachycardia

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20
Q

Norepinephrine - Adverse effects

A

Reflex bradycardia if blood pressure increases sufficiently to activate the baroreceptor reflex.

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21
Q

Epinephrine - MoA and Effects

A

Potent agonist at all alpha and beta adrenoceptors –> constricts some blood vessels and dilates others.
Increases systolic blood pressure, but can increase or decrease diastolic

Vasoconstriction (alpha1), cardiac stimulation (beta1) and bronchodilation (beta2)

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22
Q

Epinephrine - Indications

A

Anaphylactic shock
Cardiac arrest
Ventricular fibrillation
Reduction in bleeding during surgery (vasoconstrictor)
Prolongation of action of local anesthetics
Local anesthetic formulation (vasoconstrictor) –> limits systemic absorption of local anesthetic –> increases duration of action + decreases adverse effect

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23
Q

Epinephrine Lower dose VS Higher dose

A

Lower dose: greater beta2 receptors than alpha1 in vascular beds of skeletal muscle –> vasodilation and decreases diastolic BP
Higher dose: more vasoconstriction –> increases dia and sys BP

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24
Q

Dopamine - MoA and Effects

A

Activates D1 receptors, beta1 and alpha receptors, unlike the other catecholamines, dopamine also stimulates the release of norepinephrine from sympathetic neurons.

Renal vasodilation (D1), cardiac stimulation (beta1), increased BP (beta1, alpha1)

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25
Q

Dopamine - Indications

A 
Cardiogenic shock 
Septic shock
Heart failure
Hypotension
Adjunct to fluid administration in hypovolemic shock
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26
Q

Dopamine - Higher dose VS Lower dose

A

Low doses: dopamine selectively activates D1 in renal and other vascular beds, thereby cause vasodilation and an increase in renal blood flow –> NOT effective in treating/preventing acute renal failure
Higher doses: it activates beta1 in the heart–> stimulating cardiac contractility and increasing cardiac output and tissue perfusion.
At even higher doses: activates alpha1 and causes vasoconstriction

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27
Q

Isoproterenol - MoA and Effects

A

Selective beta1and beta2 adrenoceptor agonist, because it has little affinity for alpha receptors.

Cardiovascular:
Produces vasodilation and cardiac stimulation (beta1). Lowers diastolic pressure, but it can increase systolic pressure by increasing heart rate and contractility.
Respiratory: bronchodilation (beta2)

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28
Q

Isoproterenol - Indication

A

Atrioventricular block
Bradycardia
Asthma

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29
Q

Isoproterenol - Adverse effects

A

Potent chronotropic effect –> Tachycardia, Cardiac arrhythmias

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30
Q

Dobutamine - MoA and Effects

A

Primarily stimulates beta1 receptor (cardiac stimulation), with smaller effects on beta2 (vasodilation) and alpha receptors.

Cardiovascular:
Selectively increases myocardial contractility and stroke volume while producing a smaller increase in heart rate –> increase CO if heart failure
Reduces vascular resistance by activating beta2, thereby reducing the impedance to ventricular ejection.
Respiratory:vasodilation

31
Q

Dobutamine - Indication

A

Short-term management of Acute heart failure
Cardiogenic shock
Cardiac stimulation during heart surgery

32
Q

Direct - Acting Noncatecholamine

A 
Albuterol
Brimonidine
Apraclonidine
Clonidine
Dexmedetomidine
Midodrine
Oxymetazoline
Phenylephrine
Pributerol
Terbutaline
33
Q

Phenylephrine - MoA and Effect

A

Activates alpha1 adrenoceptors and causes smooth muscle contraction. This produces vasoconstriction and increases vascular resistance and blood pressure.

Ocular adm leads to contraction of the iris dilator muscle and dilation of pupil(mydriasis)

34
Q

Phenylephrine - Indication

A 
Nasal decongestant(inhibits vasodilation) in patient with viral rhinitis
Allergic rhinitis
Allergic conjunctivitis( used as ocular decongestant) 
Induce mydriasis (opthalmoscopic examination)
Hypotension and shock (IV) caused by decreased peripheral vascular resistance(hypotension by excessive doses of vasodilator drugs, drug induced shock, septic shock, neurogenic shock from spinal cord injury)
Maintain blood pressure during surgery.
35
Q

Brimonidine - MoA

A

Decreases aqueous humor formation (alpha2)

36
Q

Brimonidine - Indication

A

Postop control of intraocular pressure: open-angle glaucoma and ocular hypertension

37
Q

Midodrine - MoA

A

Selectively activates alpha1 adrenoceptors in the arteriolar and venous circulation, leading to increased systolic and diastolic BP in the standing, sitting and supine position.

38
Q

Midodrine - Indication

A

Postural(orthostatic) hypotension(people who have BP decreased when standing) ex, in diabetic autonomic neuropathy pt)
Hypotension caused by infection in infants or induced by psychotropic agents.
Hypotension in person undergoing renal dialysis.

39
Q

Midodrine - Adverse effects

A

Hypertension when persons are supine.

40
Q

Albuterol, Terbutaline and Pributerol - MoA

A

Selective beta2-adrenoceptor agonists. Causes smooth muscle relaxation. Produces bronchodilation

41
Q

Albuterol, Terbutaline and Pributerol - Indication

A

Asthma
Chronic obstructive lung disease
Terbutaline - Preterm labor –> before 37th week of gestation. Relaxes uterus and maintains pregnancy for 24 to 48h –> Tocolysis)

42
Q

Albuterol, Terbutaline and Pributerol - Adverse effects and Contraindication

A

Tachycardia
Muscle tremor
Nervousness
Terbutaline: not used in pregnant women for prevention or prolong treatment –> fatal maternal heart problems

43
Q

1st group imidazoline drug

A

Oxymetazoline

44
Q

Oxymetazoline - MoA

A

Activates alpha1-adrenoceptors and cause vasoconstriction.

45
Q

Oxymetazoline - Indication

A

Topical nasal and ocular decongestant.
Local anesthetic formulation (vasoconstrictor) –> limits systemic absorption of local anesthetic: increased duration of action + decreased adverse effect

46
Q

Oxymetazoline - Adverse effects

A

Increased BP
CNS and cardiovascular depression (if absorbed into systemic circulation and distributed to the brain)
Rebound congestion

47
Q

2nd group imidazoline drugs

A

Apraclonidine

Brimonidine

48
Q

Apraclonidine, Brimonidine - MoA

A

Activate ocular alpha2 –adrenoceptor in the ciliary body and thereby reduce aqueous humor secretion.

49
Q

Apraclonidine, Brimonidine - Indication

A

Short-term presurgical and postop control of intraocular pressure.
Open-angle glaucoma and ocular hypertension

50
Q

Apraclonidine, Brimonidine - Adverse effects

A

High rate of tachyphylaxis( rapid development of tolerance)

51
Q

3rd group of imidazoline drugs

A

Clonidine, Dexmedetomidine

52
Q

Clonidine, Dexmedetomidine - MoA

A

Activates alpha2 –adrenoceptors and imidazoline receptors in CNS. Leads to reduction in sympathetic outflow from the vasomotor center in the medulla

53
Q

Clonidine - Indication

A

Hypertension
Sedative and analgesic
Pediatric procedures/surgery: Sedation & decreased anxiety and anesthetic requirements
ADHD (attention deficit/hyperactivity disorder) in children and adolescent (by decreasing firing rate of neurons releasing norepinephrine in the prefrontal cortex –> decreases impulsivity and hyperactivity)
Drug dependence (facilitates withdrawal and abstinence from opioids, benzodiazepines, alcohol and cocaine)

54
Q

Dexmedetomidine - Indication

A

Sedative and analgesic
Sedation of intubated and mechanically ventilated patients during treatment in an intensive care setting.
Adjunct to anesthesia during surgical procedures (analgesic and sedative effect, prevent delirium during emergence from anesthesia)

55
Q

What is the advantage of dexmedetomidine?

A

Does not cause respiratory depression

56
Q

Mirabegron - MoA and Effect

A

Selective agonist of beta3-adrenoceptor.
Effect:
Detrusor muscle relaxation –> increased urinary bladder capacity

57
Q

Mirabegron - Indication

A

Overactive bladder with symptoms urge urinary incontinence, urgency, and urinary frequency.

58
Q

Mirabegron - Contraindication and Adverse effects

A

Contraindication:
Uncontrolled hypertension

Angioedema
increased BP

59
Q

Droxidopa - MoA

A

Precursor to norepinephrine and effectively increases the amount of norepinephrine produced and released –> norepinephrine acts on alpha1- receptors in the blood vessels –> vascular smooth muscle constriction –> increased BP

60
Q

Droxidopa - Indication

A

Orthotension

61
Q

Amphetamine - MoA

A

Increase in NE release, CNS stimulation

Transported into the sympathetic nerve terminal by catecholamine transporter. Once inside the sympathetic neuron, it inh storage of norepinephrine by neuronal vesicles –> increased cytoplasmic concentration of norepinephrine –> reverse transport into synapse by catecholamine transporter.

62
Q

Amphetamine - Indication and Effects

A

Narcolepsy, attention-deficit disorder

Effects: vasoconstriction, cardiac stimulation, increased BP, CNS stimulation

63
Q

Tyramine - MoA and effect

A

Rapidly degraded by MAO(monoaminooxidase) in the gut and liver.

Sympathomimetic effect: increased BP

64
Q

Cocaine - MoA

A

Inhibits catecholamine transporter located in the plasma membrane of presynaptic sympathetic neuron –> decreases neuronal reuptake of norepinephrine and increases its synaptic concentrations

65
Q

Cocaine - Effects

A 
Acts as local anesthetic 
Stimulates SNS (by blocking neuronal reuptake of norepinephrine at both peripheral and central synapses)
Produces vasoconstriction and cardiac stimulation and elevates BP.
Blocks reuptake of dopamine
66
Q

Cocaine - Adverse effects

A 
Due to vasoconstriction: ischemia, necrosis of the nasal mucosa in people who abuse cocaine. 
Severe hypertension
Cardiac damage(abuse)
67
Q

Mixed- acting adrenoceptor agonists

A

Ephedrine, Pseudoepherine, Dopamine

68
Q

Mixed- acting adrenoceptor agonists - MoA

A

Indirectly increase synaptic concentrations of norepinephrine in a manner similar to amphetamine.

69
Q

Mixed- acting adrenoceptor agonists - Indications

A

Nasal decongestant in the treatment of allergic and viral rhinitis

70
Q

Mixed- acting adrenoceptor agonists - Contraindication

A

cough and cold medications should not be used in children under 6yo

71
Q

Mixed- acting adrenoceptor agonists - Adverse effects

A 
Tachycardia
Increased BP
Urinary retention
Contraction of the sphincter muscle of bladder (esp in men w prostatic hypertrophy)
CNS stimulation and insomnia
Weight loss, appetite suppressant
72
Q

Ephedrine and pseudoephedrine - MoA

A

Activates alpha and beta adrenoceptors by direct and indirect mechanisms. They produce vasoconstriction, bronchodilation.

alpha1: vasoconstriction
beta: broncodilation

73
Q

Ephedrine and pseudoephedrine - Indication

A

Nasal decongestant in treatment of colds and allergies –> restricted in many countries due to its usage to make methamphetamine.
Bronchodilation
Hypotension
Ephedra- appetite suppressor

74
Q

Tizanidine - MoA and Indication

A

Alpha 2 agonist.

Muscle relaxant, Multiple sclerosis

Pharmacology (55 decks)

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