Review of Pharmacology - 9E (2015)

Review of Pharmacology
Cardiovascular System
128. Ans. (a) Isosorbide mononitrate (Ref: KDT 6/e p525)
It is a metabolite of isosorbide dinitrate and is also available as a separate drug. It undergoes least first pass metabolism.
129. Ans. (a) Isosorbide dinitrate (Ref: KDT 6/e p525)
• It can be administered sublingually for the treatment of acute attack of angina whereas by oral route it is used for
prophylaxis.
• Pentaerythrital tetranitrate and diltiazem are used only for prophylaxis of angina.
• Dipyridamole actually worsens angina by causing coronary steal phenomenon.
130. Ans. (b) It preferentially dilates conducting arteries without affecting resistance arterioles (Ref: KDT 6/e p523)
Nitrates cause redistribution of blood flow without affecting total coronary flow. Autoregulatory small vessels remain unaffected
whereas large conducting vessels are dilated. Nitrates are predominantly venodilators, therefore decrease mainly
preload.
131. Ans. (b) Veins express larger quantities of enzymes that generate NO from nitrates (Ref: KDT 6/e p523)
132. Ans. (c) Reduction of cardiac preload (Ref: KDT 6/e p523)
Mechanism of action of nitrates in classical angina is reduction in preload (due to venodilation) and in variant angina is
coronary vasodilation.
133. Ans. (a) Coronary vasodilation (Ref: KDT 6/e p526)
134. Ans. (b) Sublingual nitroglycerine (Ref: KDT 6/e p524, 525)
Tolerance develops to nitrates, when these are present constantly in the blood. Sublingual route leads to immediate action
of nitrates and these act for a short time. Other preparations mentioned in the question are more likely to give consistent
plasma levels of nitrates leading to development of tolerance.
135. Ans. (c) Intramuscular (Ref: KDT 6/e p525)
136. Ans. (d) Sildenafil (Ref: KDT 6/e p525)
Nitrates release NO, that acts by increasing cGMP. Phosphodiesterase inhibitors like sildenafil inhibits the breakdown of
cGMP. Concomitant use of these two drugs may result in profound hypotension.
137. Ans. (b) Nifedipine (Ref: KDT 6/e p531)
Vasodilators and peripherally acting CCBs can cause tachycardia and thus may precipitate acute attack of angina. Risk of
tachycardia is more with short acting drugs like nifedipine than with long acting agents like amlodipine.
138. Ans. (a) It acts by conversion to an active metabolite in the liver (Ref: KDT 6/e p531)
Amlodipine is the longest acting DHP. It undergoes little first pass metabolism and is distributed widely. Metabolites of
amlodipine are inactive.
139. Ans. (c) Verapamil (Ref: KDT 6/e p530)
Both verapamil and propanolol decrease the conduction through AV node and their concomitant use can result in heart
block.
140. Ans. (c) It is an inhibitor of fatty acid oxidation (Ref: Katzung 10/e p194; KDT 6/e p535-536)
141. Ans. (a) Evoke coronary steal phenomenon (Ref: KDT 6/e p535)
142. Ans. (b) Dipyridamole (Ref: KDT 6/e p535)
143. Ans. (c) Amlodipine (Ref: KDT 6/e p529)
144. Ans. (c) Pentaerythrital tetranitrate (Ref: KDT 6/e p526)
145. Ans. (b) Metoprolol (Ref: KDT 6/e p527, 528)
Beta blockers act in angina by decreasing exercise induced myocardial work. These do not cause vasodilation. Nitrates and
CCBs act by causing vasodilation.
146. Ans. (d) Nitroglycerine (transdermal) (Ref: KDT 6/e p525)
Continous presence of nitrates in blood will result in tolerance.
147. Ans. (d) Slow i.v. infusion (Ref: KDT 6/e p527)
Nitrates can be used in acute LVF by slow i.v. infusion.
148. Ans. (c) Conversion of hemoglobin to methemoglobin by sodium nitrite (Ref: KDT 6/e p527)
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