Review of Pharmacology - 9E (2015)

Autonomic Nervous System
have no effect on or β-receptors. Therefore, these may inhibit the effect of sympathetic nerve stimulation but will have no
effect on exogenous adrenaline action.
128. Ans. (b) Dilatation of pupil (Ref: KDT 6/e p143)
Stimulation of α-receptors cause mydriasis whereas tachycardia and vasodilation are due to activation of β-adrenergic
receptors.
129. Ans. (a) Acetylcholine (Ref: KDT 6/e p107)
Whenever blood pressure increases there is reflex stimulation of baroreceptors. These release ACh and depresses the heart.
130. Ans. (b) Asthma (Ref: KDT 6/e p127)
Beta-2 agonists are useful in premature uterine contractions to delay labour and not for delayed labor. Beta blockers are
used in the treatment of angina.
131. Ans. (d) Phenylephrine (Ref: KDT 6/e p127)
• Nor-adrenaline decreases the heart rate due to reflex stimulation of baroreceptors. These reflexes are lost in a
transplanted heart. However, by its β action, it can produce tachycardia.
• Phenylephrine is a selective α 1
agonist. It has no direct effect on the heart but produces bradycardia due to
reflex stimulation of baro-receptors. These reflexes are lost in a translanted heart. Therefore, it produces no
effect on heart.
132. Ans. (a) Cocaine (Ref: KDT 6/e p117)
It is a local anaesthetic agent (acts by inhibiting Na + channel in the axonal membrane) that also possesses indirect
sympathomimetic activity.
133. Ans. (a) Increase heart rate (Ref: KDT 6/e p123)
For explanation see text.
134. Ans. (b) Dobutamine (Ref. KDT 6/e p126)
135. Ans. (c) Patient’s tumor secreting almost pure adrenaline and no noradrenaline (See below)
Urinary excretion of metanephrines in excess suggests the secretion of mainly adrenaline by the tumor (metanephrine is a
metabolite of adrenaline and nor-metanephrine is a degradation product of nor-adrenaline). Adrenaline acts on -receptors
to cause increase in blood pressure (220/160 mmHg inthis case) and on β 1
receptors to cause tachycardia (160/min. in this
patient). However, it also possesses β 2
action that is responsible for vasodilation. This action is suppressed in the presence
of strong α-action. On giving α-blockers like phentolamine, this β 2
-action is unmasked leading to profound hypotension
(36/0 mm Hg in this patient). This phenomenon is known as vasomotor reversal of Dale.
136. Ans. (a) Renal vasodilatory effect (Ref: Katzung 11/e p137)
Dopamine acts on D 1
, β 1
and α 1
receptors. Stimulation of D 1
receptors cause renal vasodilation, which is useful clinically to improve
renal perfusion in shock with oligouria.
137. Ans. (c) Ephedrine (Ref: KDT 6/e p123)
• Ephedrine acts directly as well as indirectly through release of nor-adrenaline. Latter increases systolic (β 1
) as well as
diastolic (α 1
action) blood pressure. This is due to lack of β 2
mediated vasodilation.
• Adrenaline transiently increase diastolic BP which later on decreases due to its β 2
stimulatory action.
tahir99 - UnitedVRG
138. Ans. (a) The usual dose is 0.5-1 mg by i.m. route (Ref: KDT 6/e p129)
• Adrenaline 0.5 ml of 1 : 1000 solution (i.e., 0.5 mg) by i.m. route is drug of choice for anaphylactic shock. It
can also be used by s.c. route
• If not responding, it can be repeated after 5 minutes (not 2-4 hours). In desperate circumstances i.v. route can
be used but it must be diluted 10 times (i.e., 1 : 10000 concentration is used), therefore same solution cannot
be utilized, However, in rare circumstances, i.v. adrenaline can result in cerebral hemorrhage due to uncontrolled
rise in blood pressure.
Autonomic General Pharmacology
Nervous System
139. Ans. (d) 1-2 µg/kg/min (Ref: Harrison 17th/1453)
Dose of Dopamine
Effects
1-2 micro gm/kg/min Renal vasodilation (Renal dose)
2-10 micro gm/kg/min Stimulates β-1 receptors of heart
> 10 µ gm/kg/min Stimulates peripheral α receptor s leading to vasoconstriction
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