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Pharm II Unit I > 3 Adrenergic Stimulants > Flashcards

3 Adrenergic Stimulants Flashcards

1
Q

How is NE created?

A

Tyrosine hydroxylated to become I-dopa, which is then decarboxylated to dopamine (DA), which either stays as DA or is hydroxylated to NE (converted to Epi in adrenal medulla)

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2
Q

What is the rate limiting step in the synthesis of NE?

A

Conversion of tyrosine to I-dopa

This is blocked by metyrosine (Demser)

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3
Q

Drugs such as tyramine and amphetamine only have an effect if noradrenergic innervation is intact. Why?

A

Because they cause or increase the release of NE from the presynaptic terminal. No innervation, no NE to release.

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4
Q

What is the main mechanism for termination of action of NE?

A

Reputable by the presynaptic terminal

Blocked by many drugs, including antidepressents and cocaine

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5
Q

How can we measure the metabolism of NE and Epi?

A

By evaluating the concentrations of the metabolites VMA and HVA in a 24-hour urine sample

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6
Q

The sympathetic nervous system has important effects on …

A

Heart and blood vessels

Activated in response to physical activity, stress, and blood loss, to help return to homeostasis

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7
Q

The effects of sympathomimetic drugs are similar to those of SNS activation:

A

Stimulation of smooth muscle causing constriction of blood vessels in skin, kidneys, and mucous membranes (a1)

Relaxation of blood vessels supplying skeletal muscles (B2)

Stimulation of sweat and salivary glands (a, muscarinic)

Relaxation of smooth muscles in the gut and bronchial tree (B2)

Increase in rate and force of contraction of the heart (B1, B2)

Increased glycogenolysis (B2, B3)

Modulation of insulin, Renin, and pituitary hormones (B1, a)

CNS stimulation

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8
Q

Alpha1 receptors are _______ and stimulation leads to …

A

Excitatory - stimulation leads to formation of IP3, increasing Ca2+, and DAG —> activates protein kinase C

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9
Q

Alpha2 receptors are _______ and often found ________ where they act to _______ neurotransmitter release

A

Inhibitory, found presynaptically, reduce NT release

Inhibit adenylyl cyclase and decrease intracellular cAMP (Gi-protein)

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10
Q

What is the selective agonist for Alpha1 receptors?

A

Phenylephrine

Causes vasoconstriction, increased PVR, esp in small vessels

Causes vasoconstriction in nasal mucosa, decreasing congestion

Dilated pupil —> mydriasis

Causes constriction of the prostate gland

Stimulate pilomotor smooth muscle, causing erection of hair

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11
Q

What is the selective agonist for Alpha2 receptors?

A

Clonidine

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12
Q

NE and Epi have about equal affinity for ____ receptors but Epi has a higher affinity for ____ receptors.

A

B1 for both, B2 for epi

NE has little effect on B2 receptors

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13
Q

All subtypes of beta receptor activate adenylyl cyclase through a ___________

A

Gs protein —> increased intracellular cAMP

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14
Q

Selective agonist for B1 receptors?

A

Dobutamine

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15
Q

What do B2 receptors effect?

A

Increase the force and rate of contraction of the heart (positive inotropic and chronotropic effect)

Increase AV conduction velocity and automaticity

Increase renin secretion from kidney

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16
Q

Selective agonist for B2 receptors?

A

Albuterol!

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17
Q

What do B2 receptors effect?

A

Less pronounced cardiac effects that B1

Relax respiratory, uterine, GI smooth muscle

Relax blood vessels supplying skeletal muscle

Promote potassium uptake into skeletal muscle

Increase glycogenolysis and gluconeogenesis in liver

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18
Q

B3 receptors have ONE FUCKING JOB. What the fuck is it?

A

Increase lypolysis in fat cells

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19
Q

Dopamine receptors are of particular importance in ______ and _______

A

The brain and renal and splanchnic vasculature

D1: usually stimulates adenylyl cyclase —> dilation of renal blood vessels

D2: inhibit adenylyl cyclase —> open K+ channels and decrease Ca2+ influx —> inhibits release of NTs

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20
Q

Alpha receptor stimulation in the CV system:

A

Increases arterial resistance —> increase BP

The increased BP stimulates baroreceptors, which then increase vagal input to slow the heart

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21
Q

In people with _______ the baroreceptors may be impaired and the effects of the alpha agonist on BP may be magnified

A

Atherosclerosis

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22
Q

Effects of alpha agonists on the eye

A

Mydriasis (b/c radial muscle contraction)

Also increase the removal of aqueous humor, decreasing intraocular pressure - hence their use in glaucoma!

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23
Q

Effects of alpha agonists on the Respiratory tract

A

Blood vessels in the upper airway and mucous membranes contain alpha receptors —> vasoconstriction by decongestants serves to decrease nasal stuffiness

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24
Q

Effects of alpha agonists on GU tract

A

Constrict the bladder, sphincter and prostate, and promote continence

Also necessary for ejaculation

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25
Effects of beta agonists on the CV system:
Increase rate, contractility and increased conduction velocity (positive chronotropic, inotropic, and dromotropic effect) - may be counteracted to some extent by reflex responses (baroreceptors) O2 demand and consumption increased Coronary blood flow also increased B2 relax smooth muscles in blood vessels to skeletal muscle Although CO increased, dilation of blood vessels results in decreased diastolic blood pressure (systolic may increase slightly)
26
Effects of beta agonists on the eyes
Increase production of aqueous humor —> increased intraocular pressure
27
Effects of beta agonists on respiratory tract
B2 agonists relax bronchial smooth muscle and widely used to treat asthma
28
Effects of beta agonists on GU tract
Relaxation of the uterus by B2 receptors useful for treating premature contractions B2 have small degree of relaxation of the urinary bladder wall B3 relax the detrusor smooth muscle during the storage phase of the urinary bladder
29
Metabolic/endocrine effects of beta agonists
Renin secretion increased (B1) B2 promote glycogenolysis and uptake of potassium and insulin secretion B3 stimulate lipolysis in fat cells
30
Norepinephrine (Levophed) stimulates ____ and ____ receptors with little effect on ____ receptors
Alpha and B1, little effect on B2 Must be injected, very short duration due to rapid metabolism Primary effect is on BP, with slight reflexive bradycardia
31
If atropine is given prior to NE, the _______ is inhibited
Vagal reflex The baroreceptors effect will not occur, so HR will increase
32
NE can cause severe _________ at the infusion site
Vasoconstriction —> necrosis
33
Epinephrine (Adrenalin) which receptors?
Alpha, B1 and B2 —> complex effect Must be injected SC or IV and has a short duration of action due to rapid metabolism Effect depends on the dose administered
34
Dose dependence in Epi administration
If a low dose is infused slowly, b1 receptors will increase HR and conduction, coronary blood flow will increase and CO and O2 consumption increased; alpha receptors will constrict vessels —> increased BP and increased pulse pressure If a rapid infusion of high dose epi, BP will increase substantially but with less increase in HR
35
Epi is used for the treatment of ____________ to restore BP, decrease bronchospasm, decrease congestion and angioedema, and reverse CV collapse
Anaphylactic shock Used in emergency treatment for cardiac arrest and heart block as well
36
Vasoconstrictor property of epi is used to ...
Decrease diffusion of injected drugs such as local anesthetic
37
Epi can be distilled in the eye in glaucoma to ...
Increase removal and decrease production of aqueous humor
38
Epi toxicities
Tremor, throbbing headache, increased BP, and tachycardia, +/- angina
39
When is epi injection contraindicated?
People taking beta-blockers, since unopposed effects on alpha receptors may lead to severe hypertension
40
How is ephedrine different from epi?
Similar to epi but less pronounced High bioavailability and long duration (may last hours) Excreted in urine CNS stimulant, increases HR and may increase BP Causes bronchodilation
41
Phenylpropanolamine, a component of many OTC decongestants and weight loss drugs was taken off the market because...
Hemorrhagic stroke in women
42
Phenylephrine (neofrin) is a _____ selective agonist
Alpha 1 Causes vasoconstriction and increases peripheral vascular resistance —> increase in BP with reflexive decrease in HR May be used in hypotensive emergency to raise BP Also effective as a decongestant (but rebound effect) People with HTN should use caution Produces mydriasis
43
Phenylephrine does what to the eyes?
Produces mydriasis and may be used topically to dilate the eye for exam without affecting accommodation
44
How is pseudoephedrine different from phenylephrine
Also an alpha agonist and widely used OTC decongestant More effective orally than phenylephrine but people use it to make meth, so there’s that.
45
Direct acting alpha agonist which causes vasoconstriction and can be used on nasal mucosa and in the eye
Oxymetazoline (Afrin) - used as nasal spray to decrease congestion Rebound effect occurs with chronic use (down-regulation) Acts on alpha2 and could cause hypotension if large quantity absorbed systemically The eye versions (tetrahydrozoline - Visine, and naphazoline - Privine) are all contraindicated in narrow-angle glaucoma and hypertension patients
46
Oral prodrug in the same family as afrin and visine, used to treat symptomatic orthostatic hypotension
Mid o drink
47
_______ is a selective a2 agonist that acts in the brain to decrease the release of NE and other NTs, reducing overall sympathetic output to the periphery
Clonidine (Catapres) Reduced sympathetic tone —> decreased BP Administered orally or by transdermal patch for the treatment of hypertension Appears to reduce craving in recovering opioid addicts and alcoholics and decreases withdrawal Sx Patch can help decrease hot flashes in menopause May be used as a pre-anesthetic med Side effects: dry mouth, sedation, ED in men
48
What will happen if clonidine is withdrawn too abruptly?
Hypertension
49
Other alpha 2 agonists besides clonidine?
Methyldopa Apraclonidine used in eye to reduce pressure Dexmedetomidine Tizanidine has less effect on BP but is good at reducing muscle spasticity
50
___________ is a very potent select B1 and B2 agonist that increases the rate and force of contraction of the heart, with vasodilation in skeletal muscle as well as in renal and mesenteric vascular beds.
Isoproterenol (Isuprel) Systolic pressure may rise initially due to increased CO but dilation of skeletal blood vessels will lead to a decrease in BP with a reflex increase in HR Used in EM tx for cardiac arrest and complete heart block Large doses —> tachycardia, palpitations, and arrhythmias
51
Dobutamine is a _____ agonist with some effect on alpha receptors
B1 Prominent positive inotropic effect in the heart Increases CO and cardiac contractility Frequently used in cardiac stress tests if patient cannot exercise Half-life is only 2 min so effect is short
52
Terbutaline, albuterol (ventolin) are selective _______
B2 agonists with little effect on B1 receptors in normal doses Widely used for asthma H/a, tachycardia, and skeletal muscle tremor common side effects
53
Example of a beta-3 agonist
Mirabegron Used for patients with overactive bladder Side effects: nausea, headache, HTN, diarrhea, constipation, dizziness, and sinus tachycardia
54
Low doses of __________ activate receptors in renal vascular beds —> vasodilation and increasing renal blood flow, GFR, and sodium secretion
Dopamine (via D1 receptor) At high concentrations, stimulates B1 receptors in the heart, producing positive inotropic and chronotropic effect (good for cardiac shock b/c increases CO without vasoconstriction)
55
What is Fenoldopam (Corlopam)?
Select D1 receptor agonist Causes dilation of vascular beds, decreasing BP Mainly used for rapid decrease in BP in severe HTN
56
Amphetamine, Cocaine, and Tyramine are all examples of ...
Indirect acting sympathomimetics
57
Amphetamine works by ...
Increasing release of NE (and DA) esp in the CNS Used as a CNS stimulant Side effects: tremor, tachycardia, and HTN, possibly psychosis Can cause cerebral hemorrhage, convulsions, and coma at high doses Can treat enuresis because it causes strong contraction of the urinary bladder sphincter
58
Other drugs similar to amphetamine
Methamphetamine - more central actions and fewer peripheral effects; major drug of abuse Methylphenidate (Ritalin) - used in ADHD where they cause a paradoxical decrease in hyperactivity Amphetamine like compounds have been used for weigh loss but long term effect is minimal
59
How does cocaine work again?
Inhibits re-uptake of DA and NE into nerve terminals Shorter acting and more intense than amphetamine May cause severe HTN and stroke
60
How does Tyramine work?
Indirectly acting compound that will increase release of catecholamines from nerve terminals —> displace NE in storage vesicles Normally, hydrolyzed by MAO
61
In patients treated for depression with MAO inhibitors, ingestion of __________ may cause a severe ____________
Large amounts of tyramine —> severe hypertensive crisis

Pharm II Unit I (4 decks)

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