2. • Cardiotonics are the drugs which increase the
contractility of the cardiac muscle without
increase in the myocardial oxygen demand.
• Also called as ionotropic drugs.
• Commonly used for patients with heart failure.
5. Introduction
• The word digitalis is used to mean cardiac
glycosides.
• William Withering, an English physician first
described the clinical effects of digitalis in CCF in
1785.
• Obtained from the foxglove plant family.
• Digoxin is the only cardiac glycoside used
clinically, because of its favorable pharmacokinetic
properties.
6. Mechanism of action
Inhibit the enzyme Na+K+ATPase (also called sodium
pump) present on the cardiac myocytes
Accumulation of intracellular Na+
Prevents extrusion Increase Ca++ entry
of Ca++ through Ca++ channels
Increase intracellular Ca++
Increase force and velocity of contraction
Positive ionotropic effect
8. 1. Cardiac actions
• Positive inotropic effect:
▫ Increases force of contraction of heart increases
stroke volume increases cardiac output.
▫ The systole is shortened and the diastole is prolonged
which allows more rest to the heart.
▫ The ventricles are more completely emptied because of
more forceful contractions.
• Heart rate is reduced.
• Effects on electrophysiological properties
▫ Digitalis depresses AV conduction and enhances
automaticity of the ventricles and the Purkinje cells.
• Blood pressure:
▫ No significant effects in CCF patients.
▫ Pulse pressure may increase.
• Improves Coronary circulation
▫ Due to increased cardiac output and prolonged
diastole during which the coronaries get filled better.
9. 2. Extracardiac actions
• Kidney
▫ Diuresis occurs which relieves edema in CCF
patients.
• CNS
▫ High doses stimulate CTZ resulting in nausea and
vomiting.
10. Pharmacokinetics
• Digoxin can be given both oral and parenteral route.
• Digoxin is well-absorbed orally.
• Rapid onset of action within 30-120 minute (orally)
and 5-30 minutes (IV).
• Presence of food in the stomach delays absorption.
• Widely distributed throughout the body and gets
concentrated in heart, skeletal muscles, liver and
kidney.
• Primarily excreted unchanged in the urine, so
precautions to be taken for renal impairment patients.
16. Dose
• Inamrinone
▫ Loading dose is 0.5 mg/kg IV bolus, followed by the
maintenance dose of 5 – 10 μg/kg/min IV infusion,
(max 10 mg/kg in 24 hrs).
• Milrinone
▫ More potent & short lasting with fewer side effects.
▫ Loading dose is 50 mcg/kg IV bolus over 10
minutes, followed by the maintenance dose of
0.375 – 0.75 mcg/kg/min IV infusion.
17. Indications
• Short term management of severe heart failure
• Heart failure refractory to other treatments.
