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Adrenergic drugs 2017
This document discusses adrenergic drugs and their uses. It defines alpha and beta adrenergic receptors, their locations, and functions. Examples of direct and indirect acting sympathomimetic drugs are provided along with their overall actions on the heart, blood vessels, blood pressure, respiration, eyes, and metabolism. Specific drugs discussed in more detail include adrenaline, dopamine, dobutamine, ephedrine, and phenylephrine. Therapeutic uses of adrenergic drugs are outlined for conditions like hypotension, cardiac issues, bronchial asthma, mydriasis, uterine relaxation, attention deficit disorders, and obesity.
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Adrenergic drugs 2017
- 1. ADRENERGIC DRUGS For BSN1stYear Dr. Pravin Prasad 2ndYear Resident, MD Clinical Pharmacology Maharajgunj Medical Campus 14th March, 2017 (Chaitra 1, 2073),Tuesday
- 2. We will bediscussing…. ■ Overview of AdrenergicTransmission ■ Adrenergic receptors ■ Adrenergic Drugs
- 3.
- 4. Adrenergic Receptors Alpha (α)receptors Beta(β) receptors Relative potency of agonists Adrenaline (Adr) ≥ Noradrenaline (NA )> Isoprenaline (Iso) Iso > Adr > NA Antagonists Phenoxybenzamine Propanolol Coupling Protein Go/Gq/Gi Gs Effector Pathway IP3/DAG (↑), cAMP (↓), K+ channel (↑) cAMP (↑), Ca2+ channel (↑)
- 5. Alpha (α) adrenergicreceptors α1 α2 Location Post-junctional on effector organs Prejunctional Post-junctional Extra-junctional Functions • GU smooth muscle contraction • Vasoconstriction • ↑ glandular secretion • Relaxation of gut • Glycogenolysis in liver • Arrhythmia in heart • Inhibitor of transmitter release • Vasoconstriction • Decreased sympathetic flow • Decreased insulin release • Platelet aggregation
- 6. Beta(β) adrenergic receptors β1β2 β3 Location • Heart • JG cells in kidney • Bronchi • Blood vessels • Uterus • Liver • Gastro- intestinal tract • Urinary tract • Eye • Adipose tissue
- 7. Adrenergic responses Alpha (α)receptors Beta (β) receptors Rise in BP Fall in BP Little action on heart, arrhythmia at high doses ↑ rate, force and conduction velocity of heart - Bronchodilation Mydriasis, decreased aqueous secretion No effect on iris, relaxation of ciliary muscles, enhanced aqueous secretion
- 8. Adrenergic responses Alpha (α)receptors Beta (β) receptors Intestinal relaxation, contraction of sphincters Intestinal relaxation Bladder trigone contraction Detrusor relaxation Uterus contraction Relaxation
- 9. Adrenergic responses Alpha (α)receptors Beta (β) receptors Splenic capsule contraction Relaxation NM transmission facilitated Active state prolonged in fast contracting fibres, abbreviated in slow contracting fibres Decreased insulin secretion Augmented insulin and glucagon secretion
- 10. Adrenergic Drugs: Types DirectActing Sympathomimetics Indirect acting sympathomimetic s Mixed action sympathomimetics Adr, NA, Iso, Phenylephrine, Xylometazoline, Salbutamol Tyramine, Amphetamine Ephedrine, Mephentermine
- 11. Adrenergic drugs: overallactions Heart (β1) • Increases HR • Activates latent pacemakers – arrhythmia at higher doses • Force of contraction, cardiac output and oxygen consumption- increased • Increased conduction velocity – may overcome partial heart block
- 12. Adrenergic drugs: overallactions Blood vessels • Vasoconstriction (α1 and α2): cutaneous, mucous membrane, renal beds • Vasodilation (β2): skeletal muscles, liver, coronaries • Action more marked in arterioles and precapillary sphincters Blood Pressure • NA: rise in systolic, diastolic and mean BP (α) • Iso: rise in systolic BP, marked fall in diastolic BP (β1 &β2) • Adr: (slow i.v.) rise in systolic, fall in diastolic, mean BP rises
- 13. Adrenergic drugs: overallactions Respiration • Adr & Iso: potent bronchodilator (β2) • Adr: Bronchial mucosa decongestant • Toxic dose of Adr: pulmonary edema Eye • Mydriasis (α1: radial muscle contraction; poor with Adr) • Reduced aqueous formation and outflow facilitated
- 14. Adrenergic drugs: overallactions Metabolic • Causes glycogenolysis: hyperglycaemia, hyperlactacidemia • Lipolysis: rise in plasma free fatty acids, calorigenesis • Transient hyperkalemia followed by hypokalemia
- 15. Adrenaline: Adverse Effects ■s.c./i.m. injection: – Transient restlessness, headache, palpitation, anxiety, tremor and pallor ■ Marked rise in BP leading to CVA,VT/VF, angina – Large doses or inadvertent i.v. injection of Adr myocardial infarction
- 16. Adrenaline: Contraindications ■ Shouldnot be given: – During general anaesthesia (halothane): risk of arrhythmia – Patients receiving β blockers : marked rise in BP ■ Contraindications: – Hypertension – Hyperthyroid – Angina patients
- 17. Therapeutic Classification: AdrenergicDrugs Therapeutic Class Examples Pressor agents Noradrenaline, Phenylephrine, Ephedrine, Methoxamine, Dopamine, Mephentermine Cardiac stimulants Adrenaline, Dobutamine, Isoprenaline Bronchodilators Isoprenaline, Salmeterol, Salbutamol, Formeterol, Bambuterol,Terbutaline Nasal decongestants Phenylephrine, Naphazoline, Xylometazoline, Pseudoephedrine, Oxymetazoline, Phenylpropanolamine CNS stimulants Amphetamine, Methamphetamine, Dexamphetamine Anorectics Fenfluramine, Sibutramine, Dexfenfluramine Uterine relaxant Ritodrine, salbutamol, Isosuxprine,Terubtaline
- 18. Dopamine ■ Dopaminergic (D1and D2) and adrenergic (α and β1) agonist ■ Increases g.f.r. and exerts natriuretic effects (D1) ■ Normal doses: raises cardiac output and systolic BP ■ Moderately High Doses: Positive inotropic effect ■ Uses – Cardiogenic or septic shock – Severe CHF
- 19. Dobutamine ■ Derivative ofDopamine ■ Selective β1 agonist ■ Uses- ■ As an inotropic agent in pump failure accompanying: – Myocardial Infarction – Cardiac surgery ■ Short term management of severe congestive heart failure
- 20. Ephedrine ■ Mixed sympathomimeticdrug; mainly acts indirectly ■ Shows tachyphylaxis ■ Effective orally ■ Uses – Mild bronchial asthma – Hypotension during spinal anesthesia – Occasionally for postural hypotension
- 21. Phenylephrine ■ Selective α1agonist: raises BP due to vasoconstriction ■ Reduces intra-ocular pressure ■ Can be given orally as nasal decongestants ■ Topical uses: – Nasal decongestants – Mydriasis without Cycloplegia ■ Side effects:-After congestion seen
- 22. Nasal Decongestants ■ αagonist- topically produces local vasoconstriction ■ Selective α2 agonists (naphazoline, xylometazoline, oxymetazoline): longer duration of action ■ Lesser after congestion ■ Side Effects: – Initial stinging, – Impairs mucosal ciliary function on prolonged use: atrophic rhinitis and anosmia; – Systemic side effects: CNS depression, fall in BP
- 23. Indications: Vascular Uses ■Hypotensive states (shock, spinal anaesthesia, hypotensive drugs) ■ Along with local anaesthetics ■ Control of local bleeding ■ Nasal Decongestants
- 24. Indications: Cardiac Use ■Cardiac arrest (drowning, electrocution, etc.) – In combination with external cardiac massage ■ Partial or complete A-V block – Isoprenaline as temporary measure ■ Congestive Heart Failure
- 25. Indications ■ Bronchial asthma ■Allergic disorders (histamine mediated) ■ Mydriatic – Fundus examination – Wide angle glaucoma
- 26. Indications ■ Insulin Hypoglycaemia ■Nocturnal enuresis in children and urinary incontinence – Amphetamine ■ Uterine relaxant – Ritoridine: to postpone labour – Isosuxprine: threatened abortion and dysmenorrhoea
- 27. Indications: Central Uses ■Attention Deficit Hyperkinetic Disorders – Amphetamine ■ Narcolepsy – Amphetamine, Modafinil – Imipramine like drugs ■ Epilepsy – Amphetamines ■ Parkinsonism – Amphetamine ■ Obesity – Considered in severe obesity
- 28. Any queries?? ■ NextTopic: – Overview of Anti-adrenergic drugs – Drugs used in Glaucoma ■Thank you!!
Editor's Notes
- #6 Prejunctional on nerve ending; post-junctional in brain, pancreatic β cells; extra-junctional in some vessels, platelets
- #19 Normal doses: raises cardiac output and systolic BP Moderately High Doses: Positive inotropic effect (direct β1 and D1 action + that due to NA release)
- #20 Selective β1 agonist: increased force of cardiac contraction and output
- #24 Hypotensive states (shock, spinal anaesthesia, hypotensive drugs) Along with volume replacement (neurogenic and haemorrhagic shock) To maintain cerebral perfusion Not to be used in shock with marked vasoconstriction Cardiogenic shock: dopamine/dobutamine preferred Anaphylactic shock: Adrenaline 0.5 mg i.m. stat (benefits bronchospasm and laryngospasm as well) Autonomic neuropathy: oral ephedrine Along with local anaesthetics Infiltration, nerve block, spinal anaesthesia Prolonged duration of anaesthesia, systemic toxicity of local anaesthetics and local bleeding minimised Control of local bleeding Epistaxis, gastric erosions, stress ulcers Nasal Decongestants Common colds, rhinitis, blocked nose Blocked Eustachian tube Cautious use in infants and young children; hypertensive and elderly males
- #28 Narcolepsy Amphetamine: possibility of development of tolerance, abuse, behavioural abnormalities Modafinil: less dependent potential Imipramine like drugs can be used