Review of Pharmacology - 9E (2015)

Review of Pharmacology
EXPLANATIONS
Cardiovascular System
1. Ans. (d) Milrinone (Ref: Goodman and Gilman, 11/e p575, Harrison 17/e p1455)
Inotropic drugs are not used for treatment of right sided heart failure where the major treatment is diuretics and
vasodilators. Milrinone being a phosphodiesterase inhibitor act as an inodilator. Thus, this is the only inotropic drug that
should be used in right sided failure due to its ability to produce vasodilation. It is indicated in right heart failure with
pulmonary hypertension.
2. Ans. (b) Paroxysmal atrial tachycardia with fast ventricular rate (Ref: Critical care toxicology 4/e p395, Blueprint medicine by
Vincent B Young et al/28 (E-book available at internet)
Digitalis characteristically cause atrial tachycardia (paroxysmal or non-paroxysmal) with AV block, it does not cause atrial tachycardia
with fast ventricular rate.
• Ventricular premature beats and bigeminy are the most common arrhythmias caused by digitalis.
• In a patient having atrial fibrillation (AF), P waves are completely absent when no organized atrial activity is present.
Uncontrolled AF result in irregular tachycardia with ventricular rate of 80 to 140 beats per min. This is clinically
demonstrated by irregularly irregular pulse seen in AF. However, regularization of atrial fibrillation means that
complete heart block (block in conduction from atrium to ventricle) is present and thus no atrial impulse is conducted
and ventricles start to beat according to their intrinsic rate (i.e. ventricles take over the function of pacemaker).
Therefore, a regular heart rate of 40 to 60 beats per minute is seen. This regularization of atrial fibrillation is highly
suggestive of digitalis toxicity.
• Bidirectional ventricular tachycardia is an unusual tachyarrhythmia that usually resolves spontaneously after a few
seconds to a few minutes. It is often associated with severe structural heart disease or digoxin toxicity. It is also
known as biventricular tachycardia.
• Arrhythmias characteristically pointing towards the diagnosis of digitalis toxicity are non-paroxysmal atrial
tachycardia with atrio-ventricular block (Most characteristic), paroxysmal atrial tachycardia with atrioventricular
block, bidirectional ventricular tachycardia and regularization of atrial fibrillation.
3. Ans. (a) They should be started with optimum doses (Ref: Goodman and Gilman, 11/e p1336)
Clinical use of β adrenergic receptor antagonists in heart failure
• These are now recommended for routine use in patients with an ejection fraction < 35% and NYHA class II or III
symptoms in conjunction with ACE inhibitor or angiotensin-receptor antagonist, and diuretics.
• These should be initiated at very low doses, generally less than one tenth of the final target dose.
• NYHA Class IIIB and IV patients should be approached with a high level of caution; and in recently decompensated
heart failure, beta-blockers should not be used until the patients are stabilized for several days to weeks.
4. Ans. (a) Decreased activity of Na + /Ca ++ exchanger causing decreased influx of sodium and decreased efflux of Ca ++ in
the sarcolemma (Ref: Goodman and Gilman 12/e p802-803)
5. Ans. (d) Trimetazidine (Ref: CMDT – 2010/362-364)
Trimetazidine is a partial fatty acid oxidation inhibitor used for angina pectoris’
6. Ans. (b) Hyperkalemia (Ref: Katzung 11/e p216)
Digoxin toxicity can be exacerbated by:
↓ K + Quinidine Renal Failure
↓ Mg 2+
↑ Ca 2+
Verapamil
Thiazides
7. Ans. (c) Nitroprusside (Ref: Katzung 10/e p173-174; KDT 6/e p540)
• Hydralazine, minoxidil and nifedipine are primarily arteriolar dilators whereas nitroprusside is a mixed arteriolar
and venous dilator, therefore best answer here seems to be nitroprusside.
8. Ans. (c) It can be administered orally (Ref: CMDT 2014/396; KDT 6/e p507)
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