Page 7 - RxExam's Naplex Theory Review Part-1

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1. INOTROPIC AGENTS

Definition: Inotropic agents affect the contraction of the heart muscle. Positive inotropes stimulate and
increase the strength of heart muscle contraction causing the heart rate to increase. Negative inotropic
agents weaken the force of muscular contractions.

Classification:

Digoxin = Lanoxicaps, Lanoxin, Digitek
Dobutamine = Dobutrex
Milrinone = Primacor

Dose Special Notes

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Digoxin 0.125 mg to 0.25 1). Digoxin (Lanoxin) inhibits Na K ATP ase pump activity. This causes
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(Injection) mg once a day. an increase in the intracellular Ca levels, which increases the force of
(Elixir) contraction of the heart (positive inotropic action).
(Capsule)
(Tablet) 2). It is indicated for the treatment of heart failure, cardiogenic shock,
atrial flutter and fibrillation.

3). Cardiac arrhythmia (in infants) whereas anorexia, abdominal pain
and upset stomach (in adults) are early signs of Digoxin toxicities.

4). A normal therapeutic serum concentration: 0.7 to 1.4 ng/ml.

5). Hypokalemia, hypomagnesemia and hypercalcemia increase
toxicities of Digoxin.

6). Digoxin (Lanoxin) elixir contains 10% alcohol, and should be
carefully prescribed to patients on disulfiram therapy, or on drugs that
may produce disulfiram-like reactions with alcohol, such as
Chlorpropamide (Diabinese), Metronidazole (Flagyl), Cefoperazone
(Cefobid), etc.

7). The principal route of Digoxin (Lanoxin) excretion is via kidney,
therefore the administration of Digoxin (Lanoxin) is not recommended
in patients with an impaired renal function.

Dobutamine 2 to 20 1). Dobutamine (Dobutrex) is a direct acting inotropic agent with a
(Injection) mcg/kg/min. beta-1 receptor stimulation property.

2). Dobutamine (Dobutrex) is indicated for the short-term treatment
of patients with cardiac decompensation due to depressed contractility,
resulting either from organic heart disease or from cardiac surgical
procedures.

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