Digoxin

Clinical Chemistry

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Description

Digoxin is a potent cardiac glycoside widely prescribed for the treatment of patients suffering from congestive heart failure, as well as some types of cardiac arrhythmias. Digoxin intoxication is a common and serious problem in the clinical setting. Digoxin has a narrow therapeutic window, and individual response to the same dosage of drug varies greatly, often resulting in unpredictable serum drug levels. Intoxication symptoms are often indistinguishable from the original condition for which the drug was prescribed (e.g. arrhythmias) or may be non-specific (e.g. nausea and vomiting, headache). It may not be immediately apparent whether the patient has been under or overdosed, hence serum concentrations are useful in guiding treatment.

Where dose changes are being considered, the patient should ideally be at steady-state (a minimum of 7 to 21 days after initiation of therapy or last dose change, depending on renal function) prior to sample collection.

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Indications

Measurement of digoxin may be useful in the following circumstances: - dose optimisation - persistent symptoms or suspected toxicity - renal impairment - in patient populations with greater metabolic variability/polypharmacy (children, pregnancy, elderly, severe intercurrent illness) - where the formulation of the drug is altered - where there is the possibility of drug interactions N.B. the digoxin assay does NOT measure plant cardioglycosides or digitoxin.

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Sample Type

Serum, SST/Gel, minimum 2 mL (1 mL separated serum). At least 6 hours after an oral dose. Time to steady state 1 - 2 weeks.

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Reference Range

Reference ranges are provided on the report. Alternatively, please contact the laboratory for current ranges.

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Turnaround Time

Within 1 day

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Testing Frequency

Daily

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External Notes

Ideally sample 6 to 8 hours post-dose for therapeutic drug monitoring (TDM) purposes. In cases of suspected toxicity, please indicate time of last dose and sample collection.

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Patient Preparation

Blood samples should be taken at least 6-8 hours post-dose.

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Please note: the above information is subject to change and we endeavour to keep this website up to date wherever necessary.