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Class antiadrenergic drugs

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ANTI ADRENERGIC
(SYMPATHOLYTIC) DRUGS
DR RAGHU PRASADA MS
ASSISTANT PROFESSOR
DEPT. OF PHARMACOLOGY
SSIMS & RC.

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ANTI ADRENERGIC (SYMPATHOLYTIC) DRUGS
•DRUGS BLOCK THE ACTIONS OF CIRCULATING CATECHOLAMINE (EP & NE)
ON ADRENERGIC RECEPT...

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ADRENERGICRECEP
TOR
ALFA 1 ALFA2
LOCATION POST JUNCTIONAL ON EFFECTOR
ORGANS
PREJUNCTIONAL ON NERVE ENDINGS , ALSO
POST-JU...

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Class antiadrenergic drugs

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Class antiadrenergic drugs

  1. 1. ANTI ADRENERGIC (SYMPATHOLYTIC) DRUGS DR RAGHU PRASADA MS ASSISTANT PROFESSOR DEPT. OF PHARMACOLOGY SSIMS & RC.
  2. 2. ANTI ADRENERGIC (SYMPATHOLYTIC) DRUGS •DRUGS BLOCK THE ACTIONS OF CIRCULATING CATECHOLAMINE (EP & NE) ON ADRENERGIC RECEPTORS •ALSO INHIBITTHE EFFECTS OF ADRENERGIC NERVE STIMULATION
  3. 3. ADRENERGICRECEP TOR ALFA 1 ALFA2 LOCATION POST JUNCTIONAL ON EFFECTOR ORGANS PREJUNCTIONAL ON NERVE ENDINGS , ALSO POST-JUNCTIONAL IN BRAIN, PANCREATIC BETA CELLS AND EXTRA JUNCTIONAL IN BLOOD VESSELS, PLATELETS FUNCTION GI SMOOTH MUSCLES-CONTRACTION GLAND-SECRETION GUT- RELAXATION LIVER-GLYCOGENESIS HEART-ARRHYTHMIAS INHIBITION OF TRANSMITTER RELEASE VASOCONSTRICTION, DECREASED SYMPATHETIC FLOW NEGATIVE FEEDBACK CAUSES LESS NOREPINEPHRINETO BE RELEASED SO BP IS REDUCED DECREASED INSULIN RELEASE PLATELET AGGREGATION SELECTIVE AGONIST PHENYLEPHRINE METHOXAMINE CLONIDINE SELECTIVE ANTAGONIST PRAZOCIN, TERAZOCIN TAMSULOSIN YOHIMBINE, ROUWOLCINE EFFECTIVE PATHWAY IP3/DAG, PHOSHOLIPASEA2 PG RELEASE CAMP K+ channel, Ca CHANNEL, IP3 /DAG
  4. 4. ALPHA ADRENOCEPTOR ANTAGONISTS NONEQUILIBRIUM TYPE: Β-HALOALKYLAMINES: PHENOXYBENZAMINE EQUILIBRIUM: I. NONSELECTIVE: 1. ERGOTS: ERGOTAMINE AND ERGOTOXINE 2. HYDROGENATED ERGOT ALKALOIDS: DHE, DIHYDROERGOTOXINE 3. IMIDAZOLINES: TOLAZOLINE, PHENTOLAMINE 4. SELECTIVE Α-1: PRAZOSIN, TERAZOSIN, DOXAZOSIN AND TAMSULOSIN, ALFUZOSIN SELECTIVE Α-2: YOHIMBINE, IDAZOXAN
  5. 5. PHARMACOLOGICAL EFFECTS •ANTAGONISM OF Α-RECEPTORS OF ARTERIOLES & VEINS  DECREASE PVR, DECREASE BP •2) PREVENT PRESSER EFFECT OF USUAL DOSES OF Α-AGONISTS  DEPRESSOR EFFECT • POSTURAL HYPOTENSIONPOSTURE IS CHANGED FROM SITTINGTO UPRIGHT POSITION SUDDEN FALL IN BP (POOLING OF BLOOD IN EXTREMITIES DUE TO GRAVITY) •4) REFLEX TACHYCARDIA USUALLY BY NON-SELECTIVE BLOCKERS
  6. 6. PHARMACOLOGICAL EFFECTS •NASAL CONGESTION (DILATATION OF BLOOD VESSELS OF NASAL MUCOSA) 2) BLOCKING OF Α 1 RECEPTORS OF DILATOR PUPILLAE MUSCLES MIOSIS+ DECREASED INTRAOCULAR PRESSURE •3) BLOCKING OF Α 1 RECEPTORS OF TRIGONE+SPHINCTOR MUSCLES  RELAXATIONURINARY OUTFLOW
  7. 7. PHARMACOLOGICAL EFFECTS •1)NON-SPECIFIC Α 1+ Α 2 ANTAGONIST •A)PHENTOLAMINE IMIDAZOLINE-DERIVATIVE PHARMACODYNAMICS:MOA BLOCKS BOTH Α 1+ Α 2-RECEPTORS • ANTAGONISM OF Α 1–RECEPTORS (POSSIBLY Α 2) OF VASCULAR SM.MUSCLES  DECREASE PVR AND DECREASE BP  CARDIAC STIMULATION IN RESPONSE TO BAROREFLEX MECHANISM • ANTAGONISM OF PRESYNAPTIC Α 2-RECEPTORS RELEASE OF NE FROM SYMPATHETIC NERVES CARDIAC STIMULATION
  8. 8. PHARMACOLOGICAL EFFECTS •INHIBITS RESPONSE TO SEROTONIN, AGONIST OF MUSCARINIC, H1 & H2 HISTAMINE RECEPTORS •INHIBITIONOF EJACULATION – DUE TO INHIBITION OF CONTRACTION OF VAS DEFERENS AND OTHERS •CLINICAL USE: PHEOCHROMOCYTOMA, CLONIDINE WITHDRAWAL, CHEESE REACTION AND IN EXTRAVASATIONS OF NA AND ADR INJECTION PREVENT TISSUE •NECROSIS & MALE ERECTILE DYSFUNCTION •ADVERSE EFFECTS: TACHYCARDIA, ARRHYTHMIAS, MYOCARDIAL ISCHEMIA, DIARRHOEA, GASTRIC ACID PRODUCTION
  9. 9. PHENOXYBENZAMINE PHARMCODYNAMICS MOA IRREVERSIBLE (COVALENT) BINDING TO Α-RECEPTORS ( SELECTIVE FOR Α1) LONG DURATION (14-48 H) BLOCKADE EFFECTS: INHIBITS REUPTAKE OF NE BY PRE-SYNAPTIC NERVE TERMINALS BLOCKS H1, ACH & 5-HT RECEPTORS BLOCKS CATECHOL-INDUCED VASOCONSTRICTION DECREASE BP DURING HIGH SYMPATHETIC TONE (UPRIGHT POSITION) INCREASE CO  REFLEX EFFECT + BLOCKADE OF Α2 RECEPTORS
  10. 10. PHENOXYBENZAMINE •USUALLY GIVEN ORALLY  WITH LOW STARTING DOSE OF 10-20 MG/D ADVERSE EFFECTS •POSTURAL HYPOTENSION, TACHYCARDIA, NASAL STUFFINESS, INHIBITION OF EJACULATION, FATIGUE, SEDATION AND NAUSEA
  11. 11. SPECIFIC Α1 ANTAGONISTS •PRAZOSIN -PIPERAZINYL QUINAZOLINE, HIGHLY SELECTIVE FOR Α1 RECEPTORS, •LOW AFFINITY FOR Α2 ( TACHYCARDIA ) •MOA BLOCKS Α1 RELAXATION OF ARTERIAL AND VENOUS SM. MUSCLES •EXTENSIVELY METABOLIZED BY LIVER, 50% DRUG IS AVAILABLE AFTER ORAL ADMINISTRATION •TERAZOSIN- MOA REVERSIBLE Α1 SELECTIVE ANTAGONIST •USES HYPERTENSION & BENIGN PROSTATIC HYPERPLASIA (BPH) BIOAVAILABILITY - HALF LIFE IS 9-12 H
  12. 12. DOXAZOSIN •MOA HIGHLY SELECTIVE FOR Α1 RECEPTORS, •LOW AFFINITY FOR Α2 •PK: MODERATE BIOAVAILABILITY, •LONGER HALF LIFE OF ~ 22 H, EXTENSIVELY METABOLIZED •USES HYPERTENSION & BPH TAMSULOSIN MOA: COMPETITIVE Α1 ANTAGONIST, STRUCTURALLY D/F FROM OTHERS, UROSELECTIVE (VASICOSELECTIVE) - Α1A AND Α1D BUT NOT Α1B • VERY HIGH BIOAVAILABILITY, LONG HALF LIFE (9-15H)
  13. 13. TAMSULOSIN NO CHANGE IN BP AND HR AT THERAPEUTICDOSES AND POSTURAL HYPOTENSION PREFERRED DRUG IN BHP ONLY ONCE DOSING REGIME (MR CAPS) USES: EFFECTIVE FOR BPH (Α1A ) ADRS: RETROGRADE EJACULATION AND DIZZINESS
  14. 14. SPECIFIC Α2 ANTAGONISTS •TOLAZOLINE SIMILAR TO PHENTOLAMINE, •RARELY USED CLINICALLY FOR PULMONARY HYPERTENSIONIN NEW BORNE •B) YOHIMBINE -- INDOLE ALKALOID, SELECTIVE Α2 ANTAGONIST , NO CLINICAL ROLE, RESEARCH DRUG ERGOT DERIVATIVES-ERGOTAMINE, DIHYDROERGOTAMINE CAUSE REVERSIBLE Α- RECEPTOR BLOCKADE, NO CLINICAL EFFECT
  15. 15. CLINICAL USES •PHEOCHROMOCYTOMA TUMOR OF ADR.MEDULLA; RELEASES MIX OF EP, NE; PATIENTS HAVE ↑BP, TACHYCARDIA, ARRHYTHMIA •MAJOR CLINICAL USE OF PHENOX. & PHENTOLAMINE •PHENOXYBENZAMINE USED IN A) PREOPERATIVE EPISODE =ORAL DOSE OF 10-20 MG/D INCREASED IN SEVERAL DAYS B) CHRONIC TREATMENT OF INOPERABLE OR METASTATIC CONDITIONC) PHENTOLAMINE USED TO MANAGE ↑BP
  16. 16. CLINICAL USES •2) HYPERTENSIVE EMERGENCIES •LIMITED USE OF Α-ANTAGONIST, ONLY LABETALOL IS USED •3) CHRONIC HYPERTENSION MEMBERS OF PRAZOSIN FAMILY ARE EFFECTIVE FOR MILD TO MODERATE SYSTEMIC HYPERTENSIONMAJOR ADVERSE EFFECT IS POSTURAL HYPOTENSION, DIZZINESS
  17. 17. CLINICAL USES 4) PERIPHERAL VASCULAR DISEASE PHENTOLAMINE,PRAZOSIN,PHENOXYBENZAMINE RAYNAUD’SPHENOMEN; EXCESSIVE REVERSIBLE VASOSPASM IN PERIPHERAL CIRCULATION 5) LOCAL VASOCONSTRICTOR EXCESS PHENTOLAMINE REVERSE INTENSE LOCAL VASOCONSTRICTION CAUSED BY INFILTRATION OF Α-AGONISTS INTO SUBCUTANEOUS TISSUES
  18. 18. CLINICAL USES URINARY OBSTRUCTION PARTIAL REVERSAL OF SM MUSCLE CONTRACTIONIN ENLARGED PROSTATE & IN BLADDER BASE B) EFFECT ON CELLS IN PROSTATE & IMPROVE SYMPTOMS OF BPH E.G. PRAZOSIN, DOXAZOSIN & TERAZOSIN USEFUL FOR BPH + HYPERTENSIVE PATIENTS TAMSULOSIN EFFECTIVE FOR THOSE BPH PATIENTS HAVING POSTURAL HYPOTENSION 7) ERECTILE DYSFUNCTION E.G PHENTOLAMINE
  19. 19. THANK YOU Download slides from slideshare-raghuprasada authorstream-raghuprasada YOUTUBE-raghuprasada

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