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General - Pharmacology πŸ’Š > L5: Sympathomimtics > Flashcards

L5: Sympathomimtics Flashcards

1
Q

What are adrenergic agonists?

A

These drugs act either directly or indirectly (by the release of norepinephrine stored), to activate adrenergic receptors and mimic the effects of endogenous catecholamines (sympathetic stimulation)

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2
Q

Do all Sympathomimetics activate adrenergic receptors by the Same degree?

A
  • Not all sympathomimetic drugs activate the adrenergic receptors to the same degree.
  • some drugs have a higher affinity towards certain receptor classes (selectivity) depending on the ultrastructure of these receptors; however, in large doses, this selectivity is lost.
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3
Q

What is the classification of adrenergic receptors?

A

❖ According to the chemical structure
❖ According to the mechanism of action
❖ According to selectivity

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4
Q

What are adrenergic agonists classified into according to chemical structure?

A

I. Catecholamines (contain catechol nucleus)
οƒœ Natural: adrenaline, noradrenaline, dopamine
οƒœ Synthetic e.g Isoprenaline

II. Non-Catecholamines
οƒœ phenylephrine οƒœ amphetamine

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5
Q

What are adrenergic agonists classified into according to MOA?

A

A. Direct acting: e.g. E, NE, and dopamine
B. Indirect acting: e.g. amphetamine
C. Both direct and indirect: e.g. ephedrine

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6
Q

What are adrenergic agonists classified into according to selectivity?οΏΌ

A

A. Drugs acting mainly on Ξ±1 receptors: e.g. NE, phenylephrine

B. Drugs acting mainly on Ξ² receptors:
 On Ξ²1 mainly: e.g. dobutamine
 On Ξ²2 mainly: e.g. salbutamol and terbutaline
 On both Ξ²1 and Ξ²2: e.g. isoprenaline

C. Drugs acting on Ξ± and Ξ² receptors: e.g. adrenaline, ephedrine

D. Drugs acting on Ξ±, Ξ², and dopamine receptors: dopamine

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7
Q

What is the nature of epinephrine?

A

Natural alkaloid synthesized by the adrenal medulla.

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8
Q

What is the pharmacokinetics of adrenaline?

A

 It is ineffective when given orally. It should be given IM or SC.

 IV injection is highly dangerous and is likely to precipitate ventricular fibrillation (tachyarrhythmia)

 It does not cross BBB(highly polar)

 Because of the extensive metabolism (MAO, COMT) of the drug, little is excreted unchanged in the urine.

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9
Q

What is the pharmacodynamics of adrenaline?

A

Mechanism of action:
 Epinephrine Stimulates all Ξ±1,Ξ±2,Ξ²1,Ξ²2,Ξ²3 receptors.
οƒœ Ξ±1-adrenoceptors activation leads to an increase in intracellular IP3& DAG(Gq).
οƒœ Ξ²-adrenoceptors activation leads to an increase in intracellular cAMP (Gs).
οƒœ Ξ±2-adrenoceptors activation leads to decrease intracellular cAMP (Gi).

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10
Q

what are the pharmacological effects of epinephrine on the eyes?

A

οƒœ Local adrenaline: no effects (destroyed by the alkalinity of the tears).
οƒœ Local dibivalyl adrenaline (pro-drug):↓ IOP (due to VC of ciliary BV β†’ ↓ aqueous humor secretion) by a different mechanism from physostigmine

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11
Q

what are the pharmacological effects of epinephrine at CVS?

A

 Heart: Increase rate (chronotropic effect) and force (inotropic effect) of the cardiac muscle (Ξ²1)

 BP: (small dose = VD)
οƒœ Increases systolic pressure due to positive inotropic and chronotropic effects (Ξ²1),
οƒœ decreases diastolic pressure (because VD of skeletal muscle blood vessels (Ξ²2) overcomes the VC produced by Ξ±1 receptors in the skin and splanchnic vascular beds).

 Blood vessels : (Large (therapeutic) dose = VC)
οƒœ At high doses, VC (Ξ±1) of all vascular beds predominates leading to an increase in both systolic and diastolic BP.
οƒœ Increase coronary blood flow due to increased cardiac work (accumulation of metabolites), and Ξ²2 stimulation (VD).

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12
Q

what are the pharmacological effects of epinephrine on the respiratory system?

A

οƒœ Relaxation of bronchial smooth muscle (Ξ²2). = Bronchodilation
οƒœ Decrease bronchial secretions (due to VC)(Ξ±1). =bronchial decongestion.

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13
Q

What are the pharmacological effects of epinephrine on the GIT and urinary system?

A

οƒœ Wall: relaxation (Ξ²2).

οƒœ Sphincters: contraction (Ξ±1).

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14
Q

What are the pharmacological effects of epinephrine on the exocrine glands?

A

Sweat glands: sympathetic sweating (forehead and palms) (Ξ±1).

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15
Q

What is the metabolic action of epinephrine?

A

οƒœ Liver β†’ ↑ glycogenolysis (Ξ²2). (Even though insulin secretion is increased by beta two but the net effect is in favor of glycogenesis)
οƒœ Kidney β†’ ↑ renin secretion (Ξ²1)
οƒœ Fat cells β†’ ↑ lipolysis ( Ξ²3)

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16
Q

What are the local effects of epinephrine?

A

Decongestant (hemostatic), Delay absorption of drugs given SC (Toprolongs the action of anesthetics and it is due to vasoconstriction)

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17
Q

Which one causes higher VC?

Adrenaline or noradrenaline

A

Noradrenaline does, because it only affects alpha receptors and has no effect on beta receptors

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18
Q

What are the therapeutic uses of adrenaline?

A

Anaphylactic shock
Acute bronchial asthma
Cardiac arrest
Local uses

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19
Q

What are anaphylactic shocks?

A

It is a life-threatening condition (acute hypersensitivity reaction) resulting from the massive release of histamine from inflammatory cells in response to exposure to an allergic substance (e.g. penicillin). Histamine causes severe hypotension and bronchoconstriction by its effect on histamine (H1) receptors.

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20
Q

How are anaphylactic shocks treated?

A

Injection of epinephrine immediately dilates the bronchi (Ξ²2), decreases bronchial secretions (Ξ±1), and elevates BP (VC); so, epinephrine is considered the β€œphysiological antidote” of histamine as it can reverse all its effects by actions on different receptors.

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21
Q

Use of adrenaline for acute bronchial asthma

A

within minutes after s.c. administration, epinephrine:
 induces bronchodilation (Ξ²2)
 decrease airway edema (Ξ±1 )

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22
Q

Use of adrenaline for cardiac arrest

A

early i.v. epinephrine administration, during cardiopulmonary resuscitation (CPR), can restore cardiac activity (Ξ²1) and improve vascular tone collapse (Ξ±1).

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23
Q

Local uses of adrenaline

A
  • In acute epistaxis (nasal bleeding) to produce VC of nasal BV.
  • Injected locally with local anesthetics: To prolong the duration of local anesthetics due to local VC…
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24
Q

What are the adverse effects of adrenaline?

A
  1. Severe hypertension and cerebral hemorrhage.
  2. Tachycardia, palpitations, and ventricular fibrillation.
  3. Acute heart failure.
  4. Gangrene of fingers when used with local anesthetics in high concentrations (due to VC).
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25
Q

What are the contradictions of adrenaline?

A
  1. Heart diseases & Hypertension.
  2. Hyperthyroidism
  3. During general anesthesia with halothane or cyclopropane because they increase the sensitivity of the sympathetic receptors.
  4. With local anesthesia in fingers and toes
26
Q

What are the receptors for NE?

A

It activates Ξ± (mainly) and Ξ²1-receptors, It has little activity on Ξ²2-receptors

27
Q

What is the effect of NE?

A

increase both systolic and diastolic BP with reflex bradycardia.

28
Q

What is NE used for?

A

It is used as VC (by slow i.v. infusion) in acute hypotensive states.

29
Q

What is the nature of dopamine?

A

It is a natural catecholamine

30
Q

How is dopamine given?

A

Continous I.V

31
Q

What is the effect of dopamine in low (therapeutic) doses?

A

stimulates dopamine D1 receptors in renal and mesenteric vascular beds leading to VD and increase renal and hepatic blood flow

32
Q

What s the effect of dopamine in intermediate doses?

A

stimulates cardiac Ξ²1 receptors leading to increase contractility and COP.

33
Q

What is the effect of dopamine in large doses?

A

stimulates vascular Ξ±1 (stronger than D1) receptors leading to VC and ↑↑ BP

34
Q

What are the therapeutic uses of dopamine?

A

❖ Shock states: restores adequate tissue perfusion by increasing COP (Ξ²1) and increasing renal blood flow (RBF) and glomerular filtration rate (GFR; D1).

35
Q

What is the nature of dobutamine?

A

synthetic catecholamine

36
Q

What is the method of administration of dobutamine?

A

I.V infusion because of its short duration (2 min).

37
Q

What are the receptors that are affected by dobutamine?

A

It activates mainly cardiac Ξ²1-receptors with no effect on dopamine receptors leading to increase COP with little or no vascular effects.

38
Q

What are the therapeutic uses of dobutamine?

A

οƒœ cardiogenic shock(a complication of left ventricular infarction)
οƒœ It is given by continuous i.v. infusion in
οƒœ to reverse myocardial depression and increase COP (Ξ²1).

39
Q

What is the nature (chemistry) of salbutamol, terbutaline?

A

synthetic non-catecholamines

40
Q

What are the pharmacodynamics of salbutamol, terbutaline?

A

greater selectivity at Ξ²2 receptors

41
Q

What are the effects of using salbutamol, terbutaline?

A

leading to relaxation of bronchial smooth muscles, Bronchodilatationin bronchial asthma

42
Q

What are the side effects of salbutamol, terbutaline?

A

TTT

 In high doses, selectivity on Ξ²2 receptors is lost, leading to tachycardia and even arrhythmia (Ξ²1).
 Tremors
 Tolerance

43
Q

What are the nature and receptors targeted by isoprenaline (isoproterenol)?

A

Synthetic catecholamine predominantly stimulates both Ξ²1 and Ξ²2 receptors.

44
Q

What are the effects of isoprenaline?

A

It increases HR and contractility, and relax bronchial smooth muscles.

45
Q

What are the uses of isoprenaline?

A

used as a bronchodilator (rarely used)

46
Q

What is the nature of Phenylephrine, methoxamine, and midodrine? And what is their duration?

A

non-catecholamines have a long duration of action.

47
Q

What are Ξ±-adrenoceptor agonists?

A

Phenylephrine, methoxamine, midodrine, clonidine, and tizanidine.

48
Q

What is the effect of Phenylephrine, methoxamine, and midodrine?

A

They selectively stimulate Ξ±1-receptors leading to VC and increase both systolic and diastolic pressures with reflex bradycardia. (Like NE)

49
Q

What causes reflex bradycardia?

A

NE, Phenylephrine, methoxamine, and midodrine

50
Q

What are Phenylephrine, methoxamine, and medodrine Used for?

A
  1. used as vasopressors to correct hypotension.

2. could be used locally as eye or nose drops to produce VC and relieve congestion (i.e. nasal decongestants).

51
Q

What is used o relieve hypotension?

A
  • Phenylephrine, methoxamine, and midodrine

- NE (acute)

52
Q

What is the effect of clonidine?

A

It is a centrally acting Ξ±2 (inhibition of CNS)agonist leading to decrease central sympathetic outflow and blood pressure.

53
Q

What is the effect of tizanidine?

A

οƒœ It is another centrally acting Ξ±2 agonist (congener of clonidine)

οƒœ with a greater effect on presynaptic Ξ±2 in the spinal cord

οƒœ it inhibits neurotransmission

οƒœ reduces muscle spasms with minimal effect on blood pressure.

54
Q

What are the side effects of clonidine?

A

Dry mouth

55
Q

What are the uses of clonidine?

A

Antihypertensive

56
Q

What are the side effects of tizanidine?

A

Minimal SE

57
Q

What are the indirect-acting Sympathomimetics?

A

I. Releasers: Amphetamine

II. Reuptake inhibitors: Cocaine, Tricyclic antidepressants

58
Q

What are the mixed acting Sympathomimetics?

A

Ephedrine

59
Q

What is the method of administration of ephedrine?

A

Effective orally

60
Q

What are the pharmacodynamics of ephidrine?

A

Mixed effect:

  1. Indirect: release of NE from nerve endings.
  2. Direct stimulation of Ξ± and Ξ² receptors
  3. CNS stimulation.
61
Q

What are the uses of mixed-acting sympathomimetics?

A
  1. Ephedrine: nocturnal enuresis

2. Pseudoephedrine is one of the isomers of ephedrine. It is present in many nasal decongestants

62
Q

What are the side effects of ephedrine?

A

Tolerance

General - Pharmacology πŸ’Š (9 decks)

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