NUB Sympatholytics Alpha Blockers PDF

Module I Sympathetic depressants I By Staff Members of Pharmacology department Faculty of Medicine NUB Code of the module 10/11/2019 Issue 1/2018 10/11/2019 10/11/2019 1 Code of conduct Effective int...

Module I Sympathetic depressants I By Staff Members of Pharmacology department Faculty of Medicine NUB Code of the module 10/11/2019 Issue 1/2018 10/11/2019 10/11/2019 1 Code of conduct Effective interaction Switch off Mutual mobile respect phones Smile Appreciate Struggle to our be on time differences Focus on topic 10/11/2019 Intended learning outcomes (40 bold calibri) By the end of the lecture, the students will be able to: Know Classification of Sympathetic depressants Classify alpha Blockers Discuss Pharmacodynamics, uses and side effects of alpha blockers. 10/11/2019 Content Classification of Sympathetic depressants Classification of Alpha Blockers Non-Selective Alpha Blockers Selective Alpha1 Blockers Selective Alpha2 Blockers 10/11/2019  Sympathetic depressants Hypothalamus α2 Adrenergic neuron blockers β Storage Ach Release NA α1 synthesis NA α2 Ganglion blockers Receptor blocker  Non-Selective α Blockers: Selective α1 as Blockers: Selective α2 as Blockers: -Phentolamine, Prazosin, -Phenoxybenzamine Tamsulosin Yohimbine - Ergot alkaloids and doxazosin (Partial agonist)) 10/11/2019 9  Phentolamine (Regitine) *Nonselective α1& α 2 !!! Receptor Antagonist *I.M or I.V HR β1 NA NA NA α2 Ph Ph αα11 Other actions  Muscarinic: ↑G.I.T motility & secretions Histamine release  Anti-serotonin.  Indications: 1) prevention or control of hypertensive episodes of pheochromocytoma 2) Diagnosis of pheochromocytoma. 4) Peripheral Vascular Disease (P.V.D). 5) Phentolamine + papavereine I.V → induce erection  Hypotension → Reflex tachycardia, cardiac arrhythmias & myocardial infarction. G.I.T stimulation → abdominal pain, nausea, and exacerbation of peptic ulcer (M). Bronchospasm (HISTAMINE RELEASE)  Phenoxybenzamine Partially selective α1 > α2 Adrenergic Antagonist Mechanism of Action: Irreversible non-competitive blocking agent. A long-acting, α1 & α2 blocking agent. Cumulative effects for nearly a week. inhibits the reuptake 1&2 of released N.A - Anti-Muscarinic - Anti-H1 histamine - Anti-Serotonin receptors  Pheochromocytoma: for ttt & pre-oprative combined with β-blocker Shock (hypovolemic with correction of hypovolemia) P.V.D Carcinoid tumor  Side Effects  Due to the α1 blocking: Postural hypotension Tachycardia Inhibition of ejaculation Nasal congestion.  Due to the H1 blocking: Drowsiness & sedation.  Due to the Muscarinic blocking: Dry mouth.  Contraindications: conditions where a fall in blood pressure is undesirable  Prazosin Selective α1 competitive Blocker Antihypertensive No reflex tachycardia due to: Prazosin inhibits Phosphodiestrase enzyme (PDE): leads to : increase cAMP ( HR) & cGMP ( HR) The net result is constant HR Indications of prazocin 1- Hypertension. 2- Congestive Heart Failure ( Preload & Afterload) 3- Benign Prostatic Hyperplasia  o First-dose phenomenon; o marked postural hypotension and syncope o Dizziness, orthostatic hypotension o Failure of ejaculation o Salt & water retention 10/11/2019 18 Doxazosin: treat B.P.H Tamsulosin: selective α1A more effective in B.P.H  Yohimbine (Yocon)  Selective Alpha-2 Receptor Blocker  A.D.H Indications: No established clinical role. Aphrodisiac: improve erection & treat impotence Side Effects: may increase anxiety. Revision questions True or False: 1- Reflex tachycardia may occur with Prazosin. 2- Phenoxybenamine is a competitive antagonist of α receptors. 3- Beta blockers can be used alone in Pheochromocytoma. 10/11/2019 10/11/2019