Digoxin, Serum/Plasma


The main pharmacological property of the cardiac glycosides is their ability to increase the force and velocity of myocardial systolic contraction-positive inotropic (affecting the force of muscle contraction) action. The currently accepted mechanism of action of digoxin is its inhibitory action on the Na+/K+ transporting ATPase transmembrane pump of the sarcolemma. The major indication for digoxin use is the combination of congestive heart failure and atrial fibrillation. Acute left ventricular failure is usually treated with load reduction before therapy with digoxin is instituted. Another indication for use of this drug is chronic congestive failure with sinus rhythm that has failed to respond to diuretics alone.


Monitoring the drug level is performed to maintain an effective dose and avoid toxicity. The elimination half-life of digoxin in healthy subjects varies between 26 and 45 hours. Toxic effect as a result of overdose include sickness, vomiting, purging, giddiness, confused vision, objects appearing green and yellow; increased secretion of urine, slow pulse, cold sweats, convulsions, syncope and death.

Sample Type, Quantity & Conditions

1 ml Serum 1 ml K2, K3-EDTA or Na, Li-Heparin Plasma Stability: 48 Hours at Room Temperature 48 Hours at 2-8 °C 6 Months at -20 °C or Colder

Special Precautions

Usual sampling time is 6-24 Hrs after dose. Time to reach peak serum concentration for oral dose is 60-90 minutes after dosage. For I.V. peak serum concentration is reached immediately after dose administration. Separate serum or plasma from the clot or RBCs as soon as possible. Avoid grossly haemolysed samples.

Normal Range

Therapeutic Range: 0.8-2.0 ng/mL 1.02-2.56 nmol/L Toxic Level: > 2.0 ng/mL > 2.56 nmol/L

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