Digitoxin Unit Conversion

Digitoxin belongs to the family of steroidal cardio‑active glycoside drugs which exert a positive inotropic effect by increasing the intracellular Ca²⁺ concentration in cardiac muscle cells.

Several molecular mechanisms of drug actions have been discussed, with the most widely accepted that digitoxin acts by binding and inhibiting the membrane - bound Na⁺ /K⁺ ‑ATPase which ultimately increases the intracellular Ca ²⁺ concentration. As a result, both the heart’s ability to contract and its contraction amplitude increase, resulting in a greater volume of blood being transported with each beat of the heart.

Digitoxin is used to treat cardiac insufficiency. Additional indications include treatment of pronounced arterial hypertension in older patients, in preoperative settings for hypertension patients with coronary insufficiency, and for treatment of angina pectoris patients with an enlarged heart and a tendency for diastolic ventricular pressure to increase. Digitoxin is contraindicated in patients with severe ventricular arrhythmia and certain forms of pericarditis.

The therapeutic range of digitoxin is approximately 10‑25 ng/mL (13‑33 nmol/L) with 30 ng/mL (39 nmol/L) being the threshold to toxicity. In general, digitoxin exhibits much stronger protein binding than digoxin. As digitoxin has a long distribution phase blood samples should be taken 5‑6 hours after the last drug intake.

Since the digitalis effect depends on a number of factors, the therapeutic and the toxic concentration range can overlap. Serum values should therefore be interpreted only within the context of the entire clinical picture.

Digitoxin is eliminated with a half - life of 6‑8 days. It is metabolized largely in the liver. In this process, digoxin is produced out of about 10 % of the administered dose. Approximately 30 % of the digitoxin administered is eliminated by renal excretion.

Determination of the serum concentration is indicated, e.g. for digitalis therapy monitoring, for monitoring a patient’s dosing regimen, for confirming suspicion of intoxication, and in patients in which a digitalis effect was not detected in an electrocardiogram.

In the literature, the mean therapeutic serum level for digitoxin is indicated as being 13‑33 nmol/L or 10‑25 ng/mL.

Since the therapeutic and the toxic serum level can overlap, the monitoring of the glycoside levels as well as the clinical findings must be taken into consideration to clarify a possible digitalis intoxication.