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Catecholamine Actions and Adrenoceptor Agonists

Explore the roles of catecholamines, such as Dopamine and Epinephrine, on the cardiovascular and respiratory systems. Learn about the effects, clinical uses, and adverse reactions of adrenoceptor agonists.

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Catecholamine Actions and Adrenoceptor Agonists

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  1. Part 4Adrenoceptor agonists • 1. ,  receptor agonists • 2.  receptor agonists • 3.  receptor agonists

  2. Overview of catecholamine actions on CVS & respiratory systems Bronchial smooth muscle Adrenal medulla

  3. Overview of catecholamine actions on blood presure

  4. Action site of catecholamines

  5. Tyrosine Tyrosine hydroxylase Dopa Dopa decarboxylase Dopamine Dopamine -hydroxylase Norepinephrine Phenylethanolamine N-methyltransferase Epinephrine Catecholamine biosynthesis

  6. Catecholamines (儿茶酚胺) 去甲肾上腺素 肾上腺素 异丙肾上腺素 多巴胺

  7. Structure-activity relationship of catecholamines and related compounds Substitution on the aromatic nucleus COMT, central activity Substitution on the -carbon atom MAO, uptake-1, NE release Substitution on the amino group sensitivity to the subunits of receptors

  8. 1，2

  9. Metabolism of catecholamines

  10. Effect patterns of sympathomimetics

  11. Subtypes of adrenoceptors

  12. Effects of catecholamines（therapeutic doses）

  13. epinephrine  antagonist epinephrine BP Epinephrine reversal （adrenaline reversal）

  14. Epinephrine reversal (adrenaline reversal)

  15. The -adrenoceptor action of epinephrine on cardiovascular system

  16. 1. ,  receptor agonists Epinephrine 肾上腺素, Adrenaline Short action because of rapid metabolism

  17. 1. ,  receptor agonists • 1.1 Pharmacological effects • (1) Cardiac effects • 1: HR , output , • oxygen consumption , inducing arrhythmia • (2) Vascular effects • 1：vasoconstriction, especially at larger doses • 2：vasodilatation of skeletal muscles and coronary vessels

  18. 1. ,  receptor agonists • (3) Blood pressure • SP , DP  (at therapeutic doses) • (4) Bronchodilatation • 2：dilatation of bronchial smooth muscles • 1：reducing congestion and edema of bronchial mucosa • (5) Metabolic effects • blood glucose ; free fatty acids 

  19. 1. ,  receptor agonists • 1.2 Clinical uses • (1) Cardiac arrest • (2) Anaphylactic shock & other sever allergy • (3) Acute bronchial asthma • (4) Local uses • adjuvant for local anesthetics; control of bleeding

  20. Systmatic uses: Cardiac arrest Anaphylactic shock Acute bronchial asthma Topical uses: Adjuvant of local anesthesia Bleeding Clinical uses of epinephrine

  21. 1. ,  receptor agonists • 1.3 Adverse effects • (1) Cardiac arrhythmia:BP , arrhythmia • (2) Excessive rise of BP:cerebral or subarachnoid hemorrhage • (3) Central excitation：anxiety • (4) Contraindications:heart diseases, hypertension, coronary arterial disease, arteriosclerosis, hyperthyroidism

  22. 1. ,  receptor agonists Ephedrine 麻黄碱 Ephedrine 麻黄碱 Epinephrine 肾上腺素

  23. 1. ,  receptor agonists • 1.1 Pharmacological effects • Promoting release of NE, weak agonist effectson 1, 2, 1, 2 receptors • Properties： • chemically stable, orally effective； • central stimulating； • less potent and longer action duration; • tachyphylaxis.

  24. 1. ,  receptor agonists • 1.2 Clinical uses • (1) Prevention of hypotension:anesthetics • (2) Nasal decongestion:nasal drop • (3) Bronchial asthma:mild, chronic cases • (4) Relieving allergic disorders:urticaria, angioneurotic edema

  25. 1. ,  receptor agonists • 1.3 Adverse effects • (1) Central stimulation • (2) CVS effects • (3) Dependence • Pseudoephedrine(伪麻黄碱） • usually used in the compounds for treatment of cold

  26. 1. ,  receptor agonists Dopamine 多巴胺

  27. 1. ,  receptor agonists • 1.1 Pharmacological effects • (1) Cardiac effects：1 receptor, weak • (2) Vascular effects and blood pressure： • DA receptor：dilatation of renal and mesenteric arteries, blood flow (small doses); • 1 receptor：vasoconstriction of skin, mesenteric vessels (larger doses) • (3) Renal effects：renal vasodilatation; natriuretic effects

  28. Effects of dopamine on CVS Vasodilatation (DA receptor) Vasoconstriction (-adrenoceptor)

  29. 1. ,  receptor agonists • 1.2 Clinical uses • (1) Shock • cardiac and septic shock: low output, urinary volume , to be used after fully adequate replacement of intravascular fluid • (2) Acute renal failure • combined with furosemide （呋塞米） • 1.3 Adverse effects • tachycardia, arrhythmia, renal vasoconstriction

  30. 2.  receptor agonists • 2-1 1, 2 receptor agonists Norepinephrine 去甲肾上腺素, noradrenaline

  31. -adrenoceptor-mediated signal transduction

  32. 2.  receptor agonists • 2.1 Pharmacological effects • (1) Vascular effects： • 1：vasoconstriction (skin, renal, brain, hepatic, mesenteric, etc.) • vasodilatation of coronary arteries • 2：inhibiting endogenous NE release

  33. Actions of norepinephrine on post-synaptic (1) and pre-synaptic (2) receptors

  34. 2.  receptor agonists • (2) Cardiac effects： • weak direct stimulation (1); • inhibition via reflex, HR • (3) Blood pressure： • SP , DP (especially at larger doses), • larger doses:pulse pressure , tissue blood flow 

  35. 2.  receptor agonists • 2.2 Clinical uses • (1) Shock • BP , tissue blood flow , tissue damage • used in early phase of some types of shock or BP rise too slow after treatment: small doses and shorter duration

  36. 2.  receptor agonists • (2) Hypotension due to drug poisoning • for example: chlorpromazine • (3) Hemorrhage in upper alimentary tract • orally given after dilution with cold saline

  37. 2.  receptor agonists • 2.3 Adverse effects • (1) Ischemia and necrosis at the site of iv administrationrelieved by filtration with procaine or phentolamine • (2) Acute renal failureavoiding larger doses and longer duration; monitoring urinary volume • (3) Withdrawal hypotension • (4) Contraindicationhypertension, arteriosclerosis, heart diseases, severe urinary volume , microcirculation disorders

  38. 2.  receptor agonists Metaraminol 间羟胺, Aramine • Acting on  receptors directly, promoting NE release indirectly； • Weaker effects and longer duration than NE, • weak for renal vessels; • Used in early phase of shock, hypotension

  39. 2.  receptor agonists • 2-2 1 receptor agonists • used in hypotension, paroxysmal supraventricular tachycardia (by reflex)； • Mydriasis (phenylephrine): pupillary dilator muscles, no or less effect on intraocular pressure, short-acting (for several hours) Phenylephrine 去氧肾上腺素 Methoxamien 甲氧明

  40. 3.  receptor agonists • 3-1 1, 2 receptor agonists Isoproterenol 异丙肾上腺素, Isoprenaline

  41. PKA (cAMP-dependent protein kinase) -adrenoceptor-mediated signal transduction

  42. 3.  receptor agonists • 3.1 Pharmacological effects • (1) Cardiac effects • 1 receptor stimulation • (2) Vascular effects and blood pressure • 2 receptor: dilatation of skeletal muscles and coronary vessels； • SP , DP  or  , pulse pressure 

  43. 3.  receptor agonists • (3) Bronchodilatation • 2 receptor，no effect on edema of mucosa • (4) Metabolism • Promoting effects as epinephrine

  44. Effects of isoproterenol

  45. 3.  receptor agonists 3.2 Clinical uses • (1) Cardiac arrest • (2) A-V block • (3) Septic shock：low-output • (4) Acute bronchial asthma： • generally use 2 receptor agonists

  46. 3.  receptor agonists 3.3 Adverse effects • (1) Heart stimulation, arrhythmia • (2) Contraindications: • coronary heart disease, myocarditis, hyperthyroidism

  47. 3.  receptor agonists • 3-2 1 receptor agonists • Heart failure • Cardiac stimulation Dobutamine 多巴酚丁胺

  48. 3.  receptor agonists • 3-3 2 receptor agonists • Bronchial asthma Salbutemol 沙丁胺醇

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