Review of Pharmacology - 9E (2015)

Review of Pharmacology
• Brief hyperkalemia followed by hypokalemia is an important adverse effect of these agents.
• β 2
agonists do not cause hypoglycemia.
Autonomic Nervous System
115. Ans. (d) Erectile dysfunction (Ref: KDT 6/e p129, 130)
• Erection of penis requires increased blood supply by means of vasodilatation. This can be produced by α-blockers
and not by agonists. Other drugs for erectile dysfunction are phosphodiesterase inhibitors like sildenafil and tadalafil.
• Sympathomimetic agents are positive ionotropic agents and can be used for the treatment of acute decompensated
heart failure. Dopamine and dobutamine are particularly suited for this purpose.
• These agents can be used for the treatment of hypotension (dopamine) as well as hypertension (clonidine).
116. Ans. (a) IV noradrenaline increases systolic and diastolic BP and causes tachycardia (Ref: Katzung 10/e p132)
Noradrenaline increases blood pressure (both systolic and diastolic) which lead to reflex activation of baroreceptors resulting
in bradycardia. Adrenaline increases systolic BP and cause tachycardia. It has negligible effect on diastolic BP. However
both rise and fall have been noted. For details, see text.
117. Ans. (b) Dobutamine (Ref: Principles of pharmacology by HL Sharma and KK Sharma 2007/172)
• Dopamine, adrenaline and nonadrenaline are endogenous catecholamines.
• Isoprenaline, dipivefrine, dobutamine, ibopamine, dopexamine and fenoldopam are the exogenous (synthetic)
catecholamines.
118. Ans. (b) Methyl dopa (Ref: KDT 6/e p547)
Methyl dopa itself is not an a 2
agonist but it is converted to an active metabolite a-methyl norepinephrine which possesses
a 2
agonistic action. All other drugs listed in the question are a 2
agonists for the treatment of hypertension.
119. Ans. (c) Benign hyperplasia of prostate (Ref: KDT 6/e p146)
a 2
agonists like apraclonidine and brimonidine are useful for the treatment of glaucoma. Clonidine is also used for the
management of hypertension. Dexmedetomidine is a centrally acting α 2
agonist indicated for sedation of initially intubated
and mechanically ventilated patients.
120. Ans. (a) β 1
receptors in heart stimulate its contractions; (c) β 2
-receptors are present in smooth muscles (Ref: KDT 6/e p123)
121. Ans. (d) Indirect sympthomimetics involved (Ref: KDT 6/e p68; Goodmann Gilman’s 11/e p31,162, 170)
• Tachyphylaxis (Tachy-fast; phylaxis-tolerance) is the rapid development of tolerance.
• Mechanism of tachyphylaxis is incompletely understood and thought to be due to depletion of neurotransmitter
in the vesicle.
• Tachyphylaxis is usually seen with indirect acting sympathomimetics, e.g. tyramine, ephedrine, amphetamine
etc.
122. Ans. (c) Intra-muscular adrenaline hydrochloride (Ref: KDT 6/e p129)
123. Ans. (b) Ephedrine (Ref: Goodman & Gilman 11/e p239)
Catecholamines are the drugs having dihydroxybenzene nucleus in its structure. Adrenaline, isoprenaline and dopamine
contain this structure.
124. Ans. (a) Adrenaline (Ref: KDT 6/e p123)
Vasomotor reversal of dale is seen with adrenaline. When this drug is infused quickly, initially there is rise in blood
pressure (due to sitmulation of receptors) followed by prolonged fall (β 2
action). α-blocking drugs inhibit the initial rise
and only fall in blood pressure is recorded. This is known as vasomotor reversal. Nor-adrenaline has no β 2
activity and
isoprenaline lacks activity, therefore cannot demonstrate this phenomenon.
125. Ans. (a) Dopamine (Ref: KDT 6/e p126)
Dopamine has concentration dependent effects on various receptors. When infused at a rate of less than 2 µg/kg/min., it
stimulates only dopamine receptors (resulting in renal vasodilation). At 2-10 µg/kg/min. infustion rate, it stimulates β 2
receptors also and at a rate greater than 10 µg/kg/min. it causes vasoconstriction due to stimulation of -receptors.
126. Ans. (c) Secondary shock (Ref: KDT 6/e p129)
Sympathomimetic drugs are indicated in all types of shock except secondary shock. In this condition, there is reflex vasoconstriction.
Alpha blockers are useful in this type of shock.
127. Ans. (c) Do not block any effect of injected adrenaline (Ref: KDT 6/e p132, 133)
Adrenergic neuron blocking drugs like guanethidine inhibits the release of nor-adrenaline from the neuron. These drugs
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