Review of Pharmacology - 9E (2015)

General Pharmacology
126. Ans. (c) Breakdown of Gtp to Gdp (Ref: KDT 7/e p46)
Alpha subunit of G protein contains GTPase activity and thus dissociates GTP to form GDP. This result in re-uniting
subunit with β and g subunit
127. Ans. (b) Guanylyl Cyclase (Ref: KDT 7/e p47-48)
Remember that guanylyl cyclase is an enzyme while cGMP is a secondary messenger
Types of second messengers
There are three basic types of secondary messenger molecules:
Note: Calcium in the setting of G proteins is considered as the third messenger whereas the drug itself is considered as the first messenger.
128. Ans. (c) Decreases V max
(Ref: KDT 7/e p39)
• Competitive inhibitors increase K m
value whereas non-competitive inhibitors decreases V max
of an enzyme
129. Ans. (c) Activation of protein kinase (Ref: KDT 7/e p46)
• Cyclic AMP exerts most of its effects by stimulating cAMP-dependent protein kinases. These phosphorylate enzymes
resulting in their activation or inhibition.
130. Ans. (d) Pyrimethamine (Ref: KDT 7/e p66)
• Important drugs causing hemolysis in G-6-PD deficiency are
– Primaquine – Dapsone – Sulfonamides
– Nitrofurantoin – Aspirin – Menadione
– Chloroquine – Quinine – Nalidixic acid
• Sulfonamides can cause hemolysis in patients with G-6-PD deficiency and not pyrimethamine.
131. Ans. (c) Insulin (Ref: Katzung 11/e p730)
For Details, see text.
132. Ans. (c) ED 50
of the drug corresponds to the efficacy (Ref: Katzung 11/e p30-31)
ED 50
corresponds to potency of a drug, not its efficacy. All other statements are true.
133. Ans. (b) Binds to the receptor and causes opposite action (Ref: KDT 7/e p40)
134. Ans. (a) Adenosine deaminase deficiency (Ref: KDT 7/e p66)
135. Ans. (a) High affinity (Ref: KDT 6/e p42)
136. Ans. (d) Ceftriaxone (Ref: KDT 7/e p66)
137. Ans. (c) The substrate concentration at half maximal velocity (Ref: KDT 7/e p38)
K m
of an enzyme is similar to potency of a drug. It is the substrate concentration at which the velocity reaches half of the maximum
known as V max.
(similar to efficacy of a drug).Higher is the Km, lesser is the speed of the reaction.
138. Ans. (d) Adrenaline and histamine; (e) Salbutamol and leukotrienes (Ref: Katzung 12/e p20)
General Pharmacology
• Physiological antagonists are those drugs that produce opposite action by acting on different receptors.
• Adrenaline reverses the bronchoconstrictor action of histamine (via. H 1
receptors) by causing bronchodilation
(through β 2
receptors). Therefore, these are physiological antagonists.
• Salbutamol reverses the bronchoconstrictor action of leukotrienes (via cysteinyl leukotriene receptors) through its
action on β 2
receptors. Therefore, it is also a physiological antagonism.
• Isoprenaline (β 1
and β 2
agonist) and propranolol (β 1
and β 2
antagonist) are pharmacological antagonists because
they are acting on same receptors.
• Isoprenaline and salbutamol or adrenaline are not antagonists at all.
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