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a presentation about sympatholitic drugs and their mode of actions

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  1. 1.  Have the opposite effect of adrenergic agents Also known as◦ adrenergic antagonists or◦ adrenergic Blocking Agents
  2. 2. Receptor Location Mechanism followedAlpha 1 Blader, radial muscleof eye, blood vesselsGq cause constrictionAlpha 2 Smooth muscles GirelaxationBeta 1 SA, AV node, heart GsIncrease heart rateBeta 2 Blood vessels , liver,smooth musclesGsrelaxationBeta 3 lipocytes Gs
  3. 3. ◦ Synthesis of NE◦ Storage of NE in vesicles◦ Release of NE◦ Binding to receptors◦ Uptake mechanism◦ Function◦ Metabolism◦ Excretion
  4. 4. Classified by the type of adrenergic receptorthey block Alpha1 and alpha2 receptors Beta1 and beta2 and beta 3 receptors
  5. 5. PhenoxybenzamineBlock alpha 1 and alpha 2 by linking covalentlyNon selective block alpha 1 and alpha 2Block is irreversibly and new receptors are made
  6. 6. CVSVasodilatation – arteriolar and venous BPMagnitude dependent on symp. activity at that timeMore in erect that in supine position– postural hypotensionMore marked if hypovolaemia is presentBaroreflex activation– reflex tachycardia– tends to oppose the fall by  HR and CO
  7. 7. OTHER EFFECT↓contraction of trigone and sphincterin blood vessels urine flowinsulin secretion from islet cells(2 blockers)MiosisNasal stuffiness adrenergic sweating
  8. 8. α1 – blockers : Clinical usesReduce blood pressureHypertensive emergenciesLong term treatmentPhaeochromocytomaVasodilatationPeripheral vascular insufficiencyTo reverse vasoconstrictor excessImprove urine flowBenign prostatic hyperplasia
  9. 9. α1 – blockers : Adverse effects•Postural hypotension( less with α1 selective - venodilatation is less)•Reflex tachycardia ( less with α1 selective)•Salt and water retention•Nasal stuffiness•Miosis•Failure of ejaculation
  10. 10. Ergot alkaloids (ergotamine):Partial agonist & blocking propertyAlso affect other receptors (eg. 5-HT, )Therapeutic effects (migraine, uterus) notrelated to  blockade.Uses:Migraine (acute attack)Uterotonic – (methylergonovine) in PPH
  11. 11. Phenoxybenzamine: 1 > 2 ;Irreversible :Covalent binding with receptorLong duration of action (14 - 48 hrs)Also blocks 5-HT, ACh & H1 receptorsInhibits neuronal & extra-neuronal uptake of NAAbsorbed from GIT, low bioavailability
  12. 12. Clinical use:PhaeochromocytomaControl of BPPrior to surgeryAdverse effects:Postural hypotension,Tachycardia,Nasal stuffiness, ejaculationPhenoxybenzamine
  13. 13. Phentolamine : 1 = 2 PVR –  blockade + direct (non adrenergic) HR – Reflex + 2 presynaptic on cardiacsymp. terminalsPoorly absorbed orallyClinical use:PhaeochromocytomaLocal vasoconstrictor excessAdverse effects:Cardiac stimulation :- tachycardia, arrhythmia, anginaGIT Stimulation :diarrhoea;  gastric acid secretion
  14. 14. Tolazoline:Similar to phentolamineSlightly less potentBetter absorption from GITRapidly excreted in urineLimited clinical application:peripheral vasospastic disease
  15. 15. 1 Selective AgentsPrazosin & Terazosin: 1 >>>> 2Effective in management of hypertensionLow affinity for 2Relative absence of tachycardia↓ Triglycerides & LDL, ↑ HDL (favourable)Both are extensively metabolized by liverPrazosin shows high 1st Pass effect (50%)Oral absorption - goodTerazosin :Bioavailability >90%; >18 h actionUses: Hypertension and BPHAdverse effectsFirst dose effectPostural hypotensionSalt & water retention ( long term use)
  16. 16. TamsulosinSelective α1 anatgonistHas greater selectivity for α1A subtypeHas greater efficacy for BPHRelatively smaller effects on blood vesselsDoxazosin:Similar to Prazosin but longer t ½ (22 Hr)Alfuzosin : similar to prazosin
  17. 17. Clinical Uses Of  Blockers•Pheochromocytoma•Hypertensive emergencies•Chronic hypertension – non selective blockersare not used•Peripheral vascular diaease– spastic (Raynauds), not morphological•Local vasoconstrictor excess– phentolamine useful- local infiltration•Urinary obstruction – BPH– prazosin, terazosin, tamsulosin•CHFα2- selective antagonists do not have anyrecognised clinical use
  18. 18.  Block alpha & beta receptor sites(nonselective) direct or indirect acting on the release ofnorepinephrine and epinephrine Use - Cardiac arrthymias (HR), HTN (cardiac output), angina (O2 demand) SE - CHF, bronchospasm, bradycardia,wheezing
  19. 19.  Competative agonist Propanolol Acetabutol
  20. 20.  Sympatholytic1 adrenergic antagonistClass II antiarrhytmic AntihypertensiveAntianginalBronchoconstrictor Symptoms of overdose include extreme bradycardia, advancedatrioventricular block, intraventricular conductiondefects, hypotension, severe congestive heart failure, seizures, andin susceptible patients, bronchospasm, and hypoglycemia
  21. 21.  Sympatholytic1 adrenergic antagonist AntihypertensiveAntiarrhythmicAntianginalBronchoconstrictor Symptoms of an atenolol overdose include a slow heartbeat, shortness ofbreath, fainting, dizziness, weakness, confusion, nausea, and vomiting
  22. 22.  Sympatholytic1 adrenergic antagonist AntihypertensiveGlaucoma medicationBronchoconstrictor Predicted symptoms of overdose includebradycardia, congestive heart failure, hypotension,bronchospasm, and hypoglycemia.
  23. 23.  Sympatholytic adrenergic antagonist Treatment for heart failure Not expected to be toxic followingingestion.
  24. 24.  Sympatholytic adrenergic antagonist Bronchoconstrictor
  25. 25.  Sympatholytic1 adrenergic antagonist AntihypertensiveHeart failure medicationBronchoconstrictor
  26. 26.  Sympatholytic adrenergic antagonist Antihypertensive Symptoms of overdose include abdominalirritation, central nervous systemdepression, coma, extremely slowheartbeat, heart failure, lethargy, low bloodpressure, and wheezing
  27. 27.  Sympatholytic adrenergic antagonist AntihypertensiveBronchoconstrictor Symptoms of overdose includedrowsiness, vertigo, headache, andatriventricular block.
  28. 28.  www. www. Goodman & Gilman’s the pharmacologicalbasis of therapeutics 12th edition Modern pharmacology with clinicalapplications by Charles R.Craig, RobertE.Stitzel 5th edition Textbook of medical physiology 11th editionby Guyton & Hall