Which of the following statements is not true regarding DOBUTAMINE?
Ans. a (Agonist of D, and D2 receptors) (Ref. KDT Pharmacology, 6th/l26; Table 9.2)Sympathomimetics EffectApplicationDirect sympathomimetics Epinephrineb>aAnaphylaxis, open angle glaucoma, asthma, hypotension; a effects predominate at high dosesNorepinephrinea1>a2>b1Hypotension (but | renal perfusion)IsoproterenolbElectrophysiologic evaluation of tachyarrhythmias.Can worsen ischaemia.DopamineD1 = D2>b>aUnstable bradycardia, heart failure, shock; inotropic and chronotropic a effects predominate at high dosesDobutamineB1>P2-aHeart failure (inotropic > chronotropic), cardiac stress testingPhenylephrine Hypotension (vasoconstrictor), ocular procedures (mydriatic), rhinitis (decongestant)Albuterol, salmeterol, terbutalineb1>b2Albuterol for acute asthma; salmeterol for longterm asthma or COPD control; terbutaline to reduce premature uterine contractionsIndirect sympathomimetics AmphetamineIndirect general agonist, reuptake inhibitor, also releases stored catecholaminesNarcolepsy, obesity, attention deficit disorderEphedrineIndirect general agonist, releases stored catecholaminesNasal decongestion, urinary incontinence, hypotensionCocaineIndirect general agonist, reuptake inhibitorCauses vasoconstriction and local anesthesia; never give b-blockers if cocaine intoxication is suspected (can lead to unopposed al activation and extreme hypertension)DOPAMINE (DA)# It is a dopamine (D1 and D2) as well as adrenergic a and b1 (but not b2) agonist. The D1 receptors in renal and mesenteric blood vessels are the most sensitive: i.v. infusion of low dose of DA dilates these vessels (by raising intracellular cAMP) increasing g.f.r. and Na+ excretion.# Moderately high doses produce a positive inotropic (b1 action + that due to NA release), but little chronotropic effect on heart. Vasoconstriction (a, action) occurs only when large doses are infused.# At doses normally employed, it raises cardiac output and systolic BP with little effect on diastolic BP.# It has practically no effect on nonvascular a and b receptors; does not penetrate blood-brain barrier - no CNS effects.# Dopamine is used in patients of cardiogenic or septic shock and severe CHF wherein it increases BP and urine outflow.# It is administered by i.v. infusion (0.2-1 mg/min) which is regulated by monitoring BP and rate of urine formation.DOBUTAMINE# A derivative of dopamine, but not a D1 or D2 receptor agonist.# Relatively selective b1 agonist.# Though it acts on both a and b adrenergic receptors, the only prominent action of clinically employed doses (2.5-10 mg/ kg/ min i.v. infusion) is increase in force of cardiac contraction and output.# Causes no significant change in heart rate, peripheral resistance and BP.# Used as an inotropic agent in:- pump failure accompanying myocardial infarction,- cardiac surgery, and- for short-term management of severe congestive heart failure.# It is less arrhythmogenic than adrenaline.Also know:wFeaturesb1b2b31.LocatiodnHeart, JG cells in kidneyBronchi, blood vessels, uterus, g.i.t., urinary tract, eyeAdipose tissue2.Selective agonistDobutamineSalbutamol, terbutalineBRL 373443.Selective antagonistMetoprolol, AtenololICI 118551a-methyl propranololCGP 20712A (also b1)ICI 118551 (also b2)4.Potency of NA as agonistStrongWeakStrong
Agonist of D1 and D2 receptors
Derivative of dopamine
Selective beta-agonistic action
Reduced chances of arrhythmia than adrenaline
A.N.S.