Review of Pharmacology - 9E (2015)

Review of Pharmacology
111. Ans. (a) 6.25% (Ref: KDT 6/e p32)
112. Ans. (a) Half life of drug (Ref: KDT 6/e p32)
113. Ans. (b) Half life of drug (Ref: KDT 6/e p32)
• After a dosage regimen, concentration of the drug to reach the steady state (when the elimination balances the input)
is called steady state plasma concentration C pss
.
• C pss
is reached in about 4-5 half lives.
• The amplitude of fluctuations in C pss
depends on the dose interval relative to t 1/2
.
114. Ans. (d) Methotrexate (Ref: KDT 6/e p31)
115. Ans. (a) Zero order kinetics (Ref: KDT 6/e p383)
116. Ans. (a) Volume of plasma which is cleared of drug in unit of time (Ref: KDT 6/e p31)
117. Ans. (a) Phenytoin and Theophylline (Ref: KDT 6/e p31, 138)
118. Ans. (a) A constant amount of drug is eliminated per unit time (Ref: KDT 6/e p31)
119. Ans. (a) Clearance remains constant (Ref: KDT 6/e p31)
120. (b) Penicillin (Ref: Harrison 18/e p2735)
Important drugs causing SLE like syndrome include:
S
H
I
P
Sulfonamides
Hydralazine
Isoniazid
Procainamide
General Pharmacology
121. Ans. (c) Seven pass transmembrane receptors (Ref: Goodman and Gilman 12/e p52-53)
These neurotransmitters (A, NA, DA) act through G-protein coupled receptors which are also known as seven-transmembrane
domain receptors, heptahelical receptors and serpentine receptors.
122. Ans. (d) Increased cAMP (Ref: Harper, 28/e p447)
For Details, see text.
123. Ans. (c) Insulin binds to a transmembrane receptor at the outer surface of the plasma membrane, which activates the
tyrosine kinase that is the cytosolic domain of the receptor. (Ref: Goodman and Gilman 12/e p1241)
Enzymatic Receptors have two sites, the drug binds on the extracellular site and the intracellular site has enzymatic activity
(mostly tyrosine kinase). This enzyme can be activated via JAK-STAT pathway. Insulin, growth hormone, prolactin and
cytokines act via enzymatic receptors.
124. Ans. (c) G proteins act as inhibitory and excitatory because of difference in alpha subunit (Ref: Harper 26/e p458; Lippincott
Biochem 3/e p93; Ganong 22/e p41; KDT 6/e p46)
• G proteins are so-called because they bind the guanine nucleotides GDP and GTP. They are heterotrimers (i.e., made
of three different subunits)
• The three subunits are: G, Gβ and Gγ.
• In the inactive state G protein has GDP bound to its G subunit.
• When a hormone or other ligand binds to the associated receptor (GPCR), the GDP is exchanged for GTP.
• GTP activates G causing it to dissociate from GβGγ (which remain linked as a dimer).
• Activated G in turn activates an effector molecule like adenylyl cyclase, which catalyzes the conversion of ATP to
the “second messenger” cyclic AMP).
• Gs, Gi and Gq are different types of G-proteins due to different -subunits.
• Gs and Gq are stimulatory whereas Gi is inhibitory G-protein.
125. Ans. (d) Metoclopropamide (Ref: KDT 7/e p24)
• Important drugs metabolized by acetylation are
S – Sulfonamides including dapsone
H – Hydralazine
I – Isoniazid
P – Procainamide
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