Adrenergic blockers (Sympatholytic Drugs).

1. Adrenergic blockers
Nonselective
α 1 & α 2
phenoxybenzamine Irreversible noncompetitive
phentolamine
the only reversal competitive local anethetic
shorter duration of action
Adverse
effects
postural=orthostatic hypotension on standing(venodilation)
Nasal stuffiness=congestion, nausea, vomiting
Reflex Tachycardia inhibit ejaculation
uses
V.C.=Raynaud syndrome(frostbite,coldness,acrocyanosis)
pheochromocytoma = adrenalmedulla tumor before surgery
to avoid hypertensive crisis
block α1&α2 in blood vessels=V.D.& Reflex tachycardia
block presynaptic α2 = ↑N.E.= +ve ino&chronotropic effects
Epiniphrine Reversal α blocker & EPI=V.D. (β2 effect)
actions of N.E. are not reversed but diminished(decreased)
No effect on isoprenaline actions
miosis
prazosin, terazosin, doxazosin
selective α1
competitive uses
Hypertension
Not subjected to tolerance
1st dose(orthstatic hypotension=syncope less than nonselective)
1/4of dose at bed time
Benign Prostatic Hypertrophy (BPH)
Tamsulosin: potent on α1A on walls of urinary bladder & prostate
↓tone of detrusor muscle (wall relaxation) &↑urine flow
least effect on blood pressure due to higher selectivity to α1A
P.R. (both veno & arteriodilation)
minimal changes on COP, Renal blood flow, GFR
Sideeffects Headache, drowsness, ejaculation dysfunction, nasal congestion
selective α2
competitive
Yohimbine
pass BBB
treat male sexual dysfunction
Replaced by sildenafil
motor activity, tremors, B.P., H.R.
Nonselective
Β1 & β2
Propranolol
COP(-ve ino, chrono & dromotropic effect)
If bradycardia occurs,decrease the dose
Vasoconstriction=coldness of extremities(α1)
Reflex V.C. (block β1: ↓COP due to ↓contractility)
long-term therapy limitsV.C. due to limiting N.E.
Contraindicated to COPD&asthma=bronchoconstriction
‫الناس‬
‫الطبيعية‬
‫مش‬
‫هيحصلها‬
‫ضيق‬
‫فى‬
‫الشعب‬
‫الهوائية‬
‫و‬
‫ال‬
‫ضغطها‬
‫هيقل‬
Na+&H2o retention,plasma volume, V.C.
Give diuretic to prevent retention in hypertensive patients
glycolysis,glucagon=Hypoglycemia
contraindicated to Type1 dependent insulin patients
Insulin
block Isoproterenol actions
V.C. of epinephrine
aq.humor formation=treat chronic glaucoma Timolol
Nadolol
Very long duration of action 24h
uses
Hypertention
COP, Renin, sympathetic out flow from CNS
Hyperthyroidism
Inhibit T4(less active)→T3(active)
Chronic stable angina pectoris
COP, H.R., O2demand
Myocardial Infraction
Prophylactic cardioprotective from second attack
Migraine
prophylactic
Adverse
Effects
Bradycardia, severe arrhythmias=rebound hypertension
Congestive Heart Failure
long-term therapy=Up-regulation,so must be tapered off gradually for 1 week
Vived dreams,hallusination,insomnia,short memory loss, lethargy
prevents counterregulatory effects(tachycardia,tremors,anxiety, sweating)
of catecholamines during fasting hypoglycemia
kinetics
lipophilic=pass BBB= apsorbed from GIT
undergoes first pass effect
secreted in milk&pass placenta
given within meals
selectiveβ1
Esmolol:I.V. only (rapid onset & short duration)in surgery to avoid arrhythmias
Metoprolol,Atenolol,Betaxol,Bisoprolol:I.V. & orally
uses
Hypertension with bronchial asthma
DiapeticHypertension
little effect on respiratory,carbohydrate metabolism& coldness in extremitis
LDL & TG
HDL
partially antagonist
partially agonist
overdose not cause bradycardia, not pure, have Intrinsic Sympathomimetic Activity
For hypertension with bradycardia asthey donot decrease heart rate
Acebutolol(B1)