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Adrenergic (l)
This document discusses catecholamines and their roles in the sympathetic nervous system. It details the pathways of catecholamine synthesis from tyrosine to epinephrine. It describes catecholamine receptors, uptake and metabolism. It lists target organs and effects of norepinephrine, epinephrine, and dopamine. Adrenergic drugs used to stimulate or block catecholamine receptors are also outlined.
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Adrenergic (l)
- 2. Catecholamines Tyrosine Tyrosine hydroxylase L-Dopa Dopa decarboxylase Dopamine (DA) Dopamine hydroxylase Norepinephrine (NE) Phenylethanolamine--N-methyltransferase Epinephrine (Adrenaline)
- 3.
- 4. UPTAKE OF CA: It is an efficient mechanism after the release of NE Axonal uptake (Uptake 1 ) : Transports NE at a higher rate than E. Extra neuronal uptake (Uptake 2 ): CA are taken into other tissues.
- 5.
- 6. METABOLISM : by twoenzyme systems – . NE after Uptake -1 into the axoplasm is acted upon by NE which diffuses into the circulation is acted upon by , mainly in the liver The major metabolites excreted in urine is (Vanillyl mandelic acid)
- 8. • Radial fibers– • contraction –mydriasis EYE • Contraction – • increase peripheral resistance Arterioles and veins • Contraction – • urinary retention Bladder trigone and sphincter – • Glycogenolysis. Liver • Ejaculation. Vas deferens
- 9. ALPHA (α2) Acts byinhibiting adenyl cyclase – cAMP • Aggregation Platelets - • Decrease release of transmitter (NE) Prejunctional receptors – • Decrease insulin release (predominant) Pancrease --
- 10. Beta (β1) Beta receptorsstimulate adenyl cyclase– c AMP • Increase in heart rate, Force of contraction & conduction velocity Heart : • Increase renin release. JG cells in kidney
- 11. Beta (β2)receptors :cAMP • Vasodilation Blood vessels to skeletal muscle • Relaxation Uterus • Dilatation Bronchioles • Tremors Skeletal muscles • Glycogenolysis Liver -
- 12. Word of theDay: SYMPATHOMIMETIC Adrenergic drug which acts directly on adrenergic receptor, activating it. Adrenergic transmission is restricted to the sympathetic nervous system
- 13. Catecholamine Non-catecholamines • Catecholamines •Non-catecholamines Chemical classification
- 14. Norepinephrine -sites: Postganglionicsympathetic sites (except sweat glands , erector pillorie, hair follicles, ) Epinephrine- secreted by adrenal medulla Dopamine- major transmitter in basal ganglia, CTZ, imbic system, anterior pituitary.
- 15.
- 16. AGONIST α1 α2β1 β2 *** *** ** * ** ** *** *** -- -- *** *** ** -- ** -- Dobutamine -- -- ** -- Clonidine Alpha methyl Dopa -- *** -- -- *** -- -- --- -- -- -- ***
- 18. Epi→ β1receptors onventricular myocytes→ ↑ force of contraction Epi→ β1receptors at SA node →↑HR Cardiac output is determined by heart rate and stroke volume CO = HR x SV
- 19. At low plasma concentrationsof Epi, β2 effect predominates→ vasodilation At high plasma concentrations of Epi, α1 effect predominates→ vasoconstriction
- 20. Arterial BP =CO x PVR Epinephrine: ↑ CO Low doses ↓ PVR (arteriolar dilation in skeletal muscle) High doses ↑PVR
- 21. Epinephrine : Acts onα1,α 2 and β1,β2. Epinephrine increase the HR, systolic BP and PP. Its effects on diastolic blood pressure depends on dose.
- 22. Epinephrine At low dose,β2 activation predominates resulting in decrease of diastolic pressure and TPR, although mean BP may not decrease significantly. At medium dose, increase in heart rate, increase in mean blood pressure and increase in pulse pressure due to both β1 and α1 receptor action.
- 23. Norepinephrine It increases TPRand both diastolic and systolic blood pressure. Positive inotropic action results in increase of pulse pressure. Compensatory vagal reflexes tend to overcome the direct chronotropic action of NE -- reflex bradycardia may occur.
- 24. Beta agonists :β1and β2 Isoproterenol It cause a decrease in peripheral resistance, a decrease in mean BP due to β2 receptor action and a reflex increase in heart rate. Systolic blood pressure does not fall significantly as diastolic, due to β1 receptor action, so the pulse pressure increases .
- 25. • ↓arterial BP= ↑COx↓↓PVR • Decreased arterial blood pressure triggers autonomic reflex arc • Reflex tachycardia
- 28. Epi→β2-adrenergic receptors on airway smoothmuscle→ rapid, powerful relaxation→ bronchodilation
- 29. Epi at α1- adrenergic receptorson radial smooth muscle → contraction→ mydriasis Epi at B2- adrenergic receptors→ relaxation of ciliary muscle α1 β2
- 31. • peristalsis isreduced, sphincters are contracted. GIT • detrusors relaxed, trigone contracted Bladder • contracts (alpha action), RBCs are poured Splenic capsule • neuromuscular transmission is facilitated. (Tremors due to beta 2 actions) Skeletal muscle • restlessness , tremors , fall in BP and bradycardia CNS • hyperglycemia, lipolysis Metabolic : • Relaxation at term UTERUS :
- 32. Dopaminergic neurons inbrain, enteric nervous system and kidney Moderate doses DA: Stimulate DA receptors in mesenteric and renal vascular beds →vasodilatation Stimulate β1 receptors in heart →↑HR and ↑force of contraction High doses DA: Stimulate α1 receptors →vasoconstriction
- 33. • ↑ bloodflow to kidney and mesentery • ↑ cardiac output Shock (moderate doses) • Moderate doses ↑ cardiac output without ↑PVR Refractory congestive heart failure
- 34. Stimulates β1- andβ2-adrenergic receptors, but at therapeutic doses, β1-effects predominate Increases force of contraction more than increases heart rate ↑CO = ↑HR x ↑ ↑ SV Therapeutic uses Shock Refractory congestive heart failure
- 35. • Noradrenaline Dopamine •Methoxamine Mephenteramine • Ephedrine Phenylephrine PRESSOR AGENTS (α1 ) : • Epinephrine • Isoproterenol • Dobutamine. CARDIAC STIMULANTS : • Epinephrine Isoproterenol • Salbutamol Terbutaline Salmeterol BRONCHODILATORS :
- 36. • Pseudoephedrine Phenylpropanolamine •Phenylephrine Oxymetazoline • Naphazoline Xylometazoline NASAL DECONGESTANTS : • Amphetamine • Ephedrine CNS STIMULANTS : • Terbutaline • Ritodrine • Isoxsuprine UTERINE RELAXANTS :
- 37. Adrenergic drugs EPHEDRINE : Actsdirectly on alpha and beta receptors and indirectly also. Effective orally - resistant to MAO Crosses the BBB – CNS stimulation. Used in bronchial asthma and hypotension
- 38. Methoxamine Resembles phenylephrine very closely Usedoccassionally as pressor agent Phenylephrine Selective alpha1 agonist Uses: Topically as nasal decongestant For producing mydriasis. Open angle Glaucoma (by constricting ciliary body blood vessells IOP) AE: Rise in BP, After congestion
- 39. Adrenergic drugs PSEUDOEPHEDRINE Used orallyas decongestant of upper respiratory tract, nose, eustachian tube. Provides symptomatic relief in allergic rhinitis, common cold, URTI. AE: rise in BP
- 40. Adrenergic drugs IMIDAZOLINES: Naphazoline,Oxymetazoline, Xylometazoline Topical nasal decongestants After congestion less and are longer acting. Regular chronic use can cause atrophic rhinitis due to persistent vasoconstriction. AE: rise in BP
- 41. Adrenergic drugs Beta 2agonist : Salbutamol Terbutaline Albuterol Formoterol – long acting Salmeterol – long acting Ritodrine, Isoxsuprine : Uterine relaxants Uses: Delay premature labor, threated abortions
- 42. β2-selective adrenergic agonists Preferential affinity for β2- adrenergic receptors, but at sufficiently high doses, can stimulate β1 Terbutaline , Albuterol inhalation aerosol Relax bronchial smooth muscle → Bronchodilation Treatment of asthma, chronic bronchitis β2-adrenergic receptors on bronchial smooth muscle
- 43. Alpha 2 agonist: Clonidine & Alpha methyl dopa CLONIDINE: Suppression of release of NE by presynaptic alpha 2 receptors. Excellent oral bioavailability. Transdermal patches are also available. Uses: . Glaucoma. Hypertension.
- 44. Partial AV block Congestiveheart failure • Electromechanical dissociation • Drowning • Electrocution • Stroke Adam’s syndrome In cardiac arrest (intracardiac inj.Epinephrine)
- 45. • Drug ofchoice in anaphylactic shock (acute asthma). Allergic disorders (s.c ./ im. Inj.epinephrine) • Very rapid, powerful Bronchodilation Acute severe bronchial asthma • Fundus examination • Wide angle glaucoma Mydriatic • Hypotensive states • Delay absorption of local anesthetics • Control superficial bleeding • Reduce nasal congestion Vascular uses
- 46. • Narcolepsy • Obesity •Attention deficit Hyperactivity disorder (ADHD) • Nocturnal enuresis CNS Uterine relaxants
- 47. Epinephrine (contd..) • Palpitation •Restlessness, fear ,anxiety • Tremors • Increase in BP • Arrhythmia ADVERSE EFFECTS : • Hypertensive crisis • Dysrhythmiasis • Angina pectoris • Necrosis following extravasation • Hyperglycemia • IV administration CONTRAINDICATIONS Menu B F
- 48.
Editor's Notes
- #5 UPTAKE 2 (extra neuronal uptake) : CA are taken into other tissues.
- #7 COMT plays a major role in the metabolism of catecholamines particularly in liver.
- #27 Beta 1 agonists increase the HR, stroke volume and cardiac output.Beta 2 agonists decrease the total peripheral resistance.
- #33 EPINEPHRINECNS : Not significant when given IV because of poor penetration of BBB .PHARMACOKINETICS :Epinephrine, Norepinephrine and Dopamine – ORALLY INACTIVE Epinephrine and Norepinephrine are degraded by MAO and COMT of the intestine wall and liver
- #38 Phenyl Propanolamine
- #40 Alkaloid from the plant – ephedra vulgaris.Repeated injections produce tachyphylaxis.
- #44 Beta 2 agonists :Selectivity of the drugs is not absolute.Stimulation of the heart is the major adverse effect of this group.Beta 2 receptors are also seen in the skeletal muscle – tremors