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
10. 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.
11. 2. Extracardiac actions
• Kidney
▫ Diuresis occurs which relieves edema in CCF
patients.
• CNS
▫ High doses stimulate CTZ resulting in nausea and
vomiting.
12. 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.
13. Dose
• The loading dose is 0.75 – 1.25 mg orally or
0.125 – 0.25 mg IV, followed by the maintenance
dose of 0.125 – 0.25 mg/day, orally.
14. Administration
Dilution of digoxin injection:
• Digoxin injection can be administered undiluted
or diluted. Dilute 1 mL of digoxin in 4 mL of
sterile water for injection, D5W, or 0.9% NaCl.
15. Loading dose
• One-half the loading dose given immediately IV
or PO
• One-fourth the loading dose given 8 to 12 hours
later IV or PO
• The remaining one-fourth loading dose given
after an additional 8 to 12 hours IV or PO
• Administer IV slow push over 5 to 10 minutes
• Obtain ECG 6 hours after digitalizing dose to
assess for toxicity
Maintenance dose
• should be started 12 hours after the loading dose
is completed
16. Indications
• CCF
• Arrhythmias
▫ Atrial flutter - reduces the ventricular rate
▫ Atrial fibrillation - reduces the ventricular rate
▫ Atrial tachycardia- digoxin is an alternative to
verapamil.
17. Contraindications
• Hypokalemia - enhances toxicity
• MI, thyrotoxicosis patients and elderly - more
prone to arrhythmias.
• Acid base imbalance - prone to toxicity
19. Digoxin toxicity
• The usual therapeutic range is 1–2 ng/ml.
• Toxic plasma level is above 2.4 ng/ml.
20. Symptoms
• Anorexia
• Nausea
• Vomiting
• Diarrhea
• Palpitation
• Irregular heart block,
Bradycardia, Junctional
tachycardia
• Confusion
• Lethargy
• Visual changes
▫ Halos or rings of light
around objects
▫ Seeing lights or bright
spots
▫ Changes in colour
perception –especially
yellow, green
▫ Blind spots in vision
21. Treatment of digoxin toxicity
• Stop digitalis.
• Stop diuretics if given concurrently.
• Determine serum digoxin level
• Determine electrolytes, particularly serum K,
Mg, and Ca, and treat any abnormalities
• Oral or parenteral K+ supplements are given.
• Obtain continuous ECG monitoring and treat
arrhythmias
22. • Ventricular arrhythmias are treated with IV
lignocaine.
• Bradycardia is treated with IM/IV atropine.
• Supraventricular arrhythmias is treated with IV
propranolol.
• Gastric lavage for acute toxicity to limit digoxin
absorption.
• In severe toxicity - antidigoxin
immunotherapy (antidigoxin antibodies) IV
infusion (digoxin Fab - digibind) which is an
antidote.
• Digibind IV over 30 minutes.
23. Drug interactions
• Drugs that enhance digoxin toxicity
▫ Diuretics (due to hypokalaemia)
▫ Quinidine
▫ Calcium
▫ Verapamil
▫ Methyldopa
• Drugs that reduce digoxin levels
▫ Antacids, neomycin, metoclopramide- decrease
absorption
▫ Rifampicin, phenobarbitone - accelerate metabolism
due to enzyme induction
28. 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.
29. Indications
• Short term management of severe heart failure
• Heart failure refractory to other treatments.
31. Nursing implication
• Serum digoxin estimation at least 4 hrs after IV
dose and 6 hrs after oral dose.
• IV digoxin slowly over 5 minutes.
• Assess the manifestations of digoxin toxicity.
• Hold the digoxin if the heart rate below 60
beats/min.
• Assess electrolyte levels especially potassium,
magnesium.
• Monitor for drug interactions.
32. • Monitor apical pulse for 1 minute before
administering the drug to monitor for adverse
effects.
• Maintain emergency equipment ready.
• IM injection of digoxin should be discouraged,
as absorption is only 80% compared to IV; local
irritation, muscle damage, and necrosis may also
occur
