5. adrenergic drugs


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5. adrenergic drugs

  1. 1. Adrenergic drugs (Sympathomimetics( Dr. Heba A. Mahmoud(
  2. 2. Lippincott’s pharmacology 4th edition drugs Adrenergic transmission Adrenergic transmission
  3. 3. Adrenergic receptors The adrenergic receptors are classified as αand β receptors. Both classes have subtypes : • Alpha adrenoceptors (α): α1 adrenergic receptors α2 adrenergic receptors • Beta- receptors (β): Beta 1 (β1) Beta 2 (β2) Beta 3 (β3)
  4. 4. Lippincott’s pharmacology 4th edition Presynaptic β2 facilitate release of noradrenaline β3 Increase lipolysis Major effects mediated by adrenoceptors
  5. 5. Mechanism of action of the adrenergic agonists Direct-acting Indirect- acting Selective Non-selective Ephedrine Amphetamine α1:phenylephrine α2: Alpha methyl Dopa β1:dobutamine β2:salbutamol α1,α2,β1,β2:adrenaline α1,α2,β1: noradrenaline β1,β2: isoprinaline Sympathomimetic drugs Drugs have effects similar to those produced by activity of sympathetic nerve stimulation
  6. 6. Mechanism of action of the adrenergic agonists Mechanism of action of the adrenergic agonists Lippincott’s pharmacology 4th edition
  7. 7. Effects of sympathetic stimulationEffector organs Effects of sympathetic stimulation Eye Mydriasis Heart ↑ heart rate ↑ force of contraction ↑ blood pressure Blood vessels Dilatation of coronary arteries Dilatation of blood vessels supply skeletal muscle Stomach and Intestine Inhibits Peristalsis and the tone of↑ sphincters and inhibits defecation Urinary bladder Relaxes bladder wall ↑ the tone of sphincters inhibits micturation Respiratory system Dilatation of bronchi liver Glycogenlysis
  8. 8. Adrenaline α1, α2, β1 and β2 agonist Can be administered by : -- subcutaneous -- inhalation -- eye drops -- intracardiac Actions similar to sympathetic stimulation Cardiovascular system  Heart : ↑all cardiac properties (↑contractility, heart rate , AV conduction, excitability, automaticity  Blood vessels: • Vasoconstriction (skin, mucous membrane, renal) • Vasodilatation (skeletal muscle, coronary blood vessels)  Blood pressure: • ↑systolic blood pressure, ↓ diastolic blood pressure
  9. 9. Adrenaline actions (cont.) Respiratory system  Bronchodilatation (β2)  Decongestion of bronchial mucosa (α1) urinary bladder and Gastrointestinal tract  Spasm of spincters (α1)  Relaxation of the wall (β2) urinary retention and inhibits defecation Skeletal muscle  Facilitate NM transmission  Vasodilatation (β2)
  10. 10. Adrenaline actions (cont.) Eye  Vasoconstriction of conjunctival blood vessels (decongestion)  ↓intraocular pressure  Mydriasis Antiallergic Adrenaline is Physiological antagonist of histamine Metabolism  Increase blood glucose  Lipolysis  General stimulation of metabolic activity
  11. 11. Adrenaline Uses  With local anesthetic (delay absorption and prolong duration of drugs)  Open angle glaucoma (eye drops)  Epistaxis (haemostatic nasal pack)  Anaphylactic shock  Cardiac resuscitation in cardiac arrest  Acute bronchial asthma
  12. 12. Adrenaline Adverse effects  Gangrene if injected around finger toes  Hypertension , leads to cerebral hemorrhage  Tachycardia, palpitation, angina and arrhythmia Contraindications  Injection Around finger or toe  Hypertension  coronary heart disease  Arrhythmia  Hemorrhagic shock  Thyrotoxicosis
  13. 13. Isoprenaline Non-selective β agonists (stimulate β1 and β2 ): Actions: Myocardium contraction & Tachycardia  ↑ BP Bronchodilatation Uses: cardiogenic shock Asthma
  14. 14. Dopamine Non-selective α , β , D agonists Actions  Small dose:D1»vasodilatation--------------»↑renal blood flow  Moderate dose:D1+β1-------» positive inotropic effect  Large dose:α1 ------»vasoconstriction »↑peripheral resistance Uses  Shock  Resistant heart failure
  15. 15. Dobutamine (dobutrex) Selective β1agonist positive inotropic  ↑ Cardiac output  Used by I.V. infusion in treatment of -Cardiogenic shock, -Resistant heart failure -Resistant heart block. Side effects: Angina and arrhythmias
  16. 16. Phenylephrine Selective α1 – agonists Example : Action stimulates α-receptors leading to VC and ↑ blood pressure VC of mucous membrane blood vessels so promote drainage in nasal passages Uses: Nasal congestion, Hypotensive states (shock) To prolong action of local anesthetics Fundoscopic examination of eye Adverse effects : Mydriasis Urine retention
  17. 17. Alpha methyl Dopa (Aldomet)  Selective α2 – agonists Agonists of α2 receptors in VMC in brain leading to: ↓ sympathetic Outflow from vaso Motor Centre (VMC)  ↓ heart rate, ↓ CO (cardiac out put), ↓ PR  ↓ BP  It inhibits synthesis of catecholamine, dopamine and serotonin . Uses Hypertension especially in: Renal impairment. Pregnancy.
  18. 18. Selective Beta-2 agonists Actions: Bronchodilation e.g. Salbutamol Uterine relaxation Relaxation of uterine smooth muscle e.g. Ritodrine Vasodilatation e.g. Isoxuprine & Ritodrine
  19. 19. Therapeutic uses of selective β2 agonists: Bronchial asthma: acute attack, prophylaxis & status asthmaticus. Congestive heart failure. premature labor Peripheral vascular diseases. Adverse effects (large oral doses)  Tremors, tachycardia, palpitation, flushing  headache , Insomnia and confusion  Hyperglycemia Selective Beta-2 agonists
  20. 20. THANK YOUTHANK YOU Thank you