Digoxin Testing

Digoxin Test Results: What are they?

Digoxin is a naturally occurring substance found in the body. It is used in medicine, food processing, and industrial purposes. It was first discovered in Japan during the Edo period (1603-1867). Since then it has been widely used worldwide for its medicinal properties.

Digoxin is classified into two groups: Dibenzoylmethane (DBM) and Dibenzo[a]pyrene (BZP). DBM is known to cause cancer, while BZP causes birth defects. They have different biological activity.

Degradation of either group results in formation of other compounds called free radicals. These free radical molecules damage cellular components such as DNA and proteins causing cell death or changes in normal functions.

The most common form of digoxin toxicity is acute poisoning caused by ingestion of large amounts of DBMs. This type of toxic effect occurs within hours after exposure and may result in coma, seizures, respiratory failure, liver failure and even death. BZPs are usually absorbed through the skin or mucous membranes and accumulate in tissues.

Acute poisoning from these substances causes similar symptoms to those seen with DBMs but may take longer to develop.

Long-term exposure to digoxin also affects the heart by increasing the risk of arrhythmias. Severe poisoning causes changes in the electrical activity of the heart that may lead to an irregular heartbeat or even sudden cardiac arrest.

Who can be exposed to digoxin?

Anyone who has been recently exposed to this toxin is at risk, but certain people are at higher risk than others. This includes people who use or have used medication containing digoxin, people who work in a laboratory where this substance is used, and healthcare professionals.

How digoxin testing is done?

The lab results will show up in the form of a numerical value that indicates the presence and concentration of digoxin in the sample. A high value may indicate exposure, whereas a lower number may mean no or little exposure.

Whether or not lab values are actually useful in providing information about poisoning symptoms is still under debate. It is known that the concentration of digoxin in an individual’s body can vary according to age, weight, medical and diet history, medication used, exposure to broken or damaged pharmaceutical vials, and even stress. In addition, the presence of other drugs or the level of alcohol in the system may interfere with test results.

How long does digoxin stay in your body?

Digoxin has a half-life of 3 to 4 days, which means that the level decreases by half within this period. The clearance from the body is primarily renal (70% – 80%). In some people, digoxin is also excreted in the bile.

Digoxin toxicokinetics

The initial step in digoxin toxicokinetics is uptake from the blood into the tissue, which mainly occurs in the liver, gallbladder, kidney and intestines. This uptake process may take 2 to 3 days and can be interrupted by other drugs that are fat soluble.

The second step is known as biotransformation, in which the digoxin molecule is changed into several different compounds (a process also known as pharmacokinetic optimization). These compounds are mainly glucuronide conjugates. Biotransformation occurs mainly in the liver and takes about 1 to 2 days to complete.

This step can be interrupted by other drugs.

The final step in toxicokinetics is excretion of digoxin from the body, mainly through the urine. This process takes about 3 days and can be interrupted by certain drugs or dietary components such as high-fat foods, fiber containing foods and some herbal supplements.

Reviewed by April Cashin-Garbutt, BA Hons (Cantab)

Further Reading

Sources & references used in this article:

Comparison of serum digoxin level measurement with acetyl strophanthidin tolerance testing by MD KLEIN, B Lown, I Barr, F Hagemeijer, H Garrison… – Circulation, 1974 – Am Heart Assoc

Three-years’ experience in interlaboratory testing of commercial digoxin kits. by JR Hansell – American journal of clinical pathology, 1976 – europepmc.org

A unitized enzyme-labeled immunometric digoxin assay suitable for rapid testing by RG Sommer, TL Belchak, ML Bloczynski… – Clinical …, 1990 – academic.oup.com