Digoxin: The Dispensing Safety Checklist

📋 First Dispense Essentials

Mandatory items to issue

• Confirm the indication: usually atrial fibrillation (AF), atrial flutter, or heart failure. Record the indication, dose, and formulation on the pharmacy medication record.^1,4,5
• Confirm from the prescription record, discharge letter, shared care record, or prescriber confirmation that baseline blood tests were completed before starting treatment: urea and electrolytes (U&E) including potassium and sodium, serum creatinine, calcium, magnesium, and thyroid function tests.^2,3
• If a serum digoxin level is requested, the sample must be taken no less than 6 hours after the last dose, and ideally 8 to 12 hours after. Samples taken earlier give falsely elevated results and are a common source of unnecessary dose reductions. Routine serum digoxin level monitoring is not recommended.²
• Check that the dose is prescribed and dispensed in micrograms, not milligrams. Three tablet strengths are available: 62.5 microgram, 125 microgram, and 250 microgram. These are not interchangeable without prescriber instruction.⁴

Baseline clinical checks

• Serum potassium: low potassium greatly increases the risk of digoxin toxicity and can cause serious arrhythmias even when the digoxin level appears normal.⁴
• Serum magnesium: hypomagnesaemia also predisposes to toxicity. Long-term use of proton pump inhibitors (PPIs) is a recognised cause of low magnesium and should prompt more frequent monitoring.²
• Calcium: hypercalcaemia increases digoxin toxicity risk. Hypocalcaemia may indicate low magnesium.⁴
• Renal function: digoxin is largely cleared by the kidneys. Even a modest decline in kidney function can cause levels to rise rapidly.³
• Thyroid function: hypothyroidism increases sensitivity to digoxin and may require a lower dose. Hyperthyroidism causes relative resistance, and the dose may need to be higher. Thyroid status should be reassessed whenever digoxin appears ineffective or unexpectedly toxic.⁴

Key risks and lifestyle traps

• Amiodarone can substantially increase digoxin concentrations by inhibiting renal excretion. When amiodarone is started, confirm that the prescriber has reviewed the digoxin dose and arranged a monitoring plan. This interaction is frequently missed when patients are started on amiodarone in hospital and discharged without a digoxin review.⁴
• Verapamil and diltiazem both raise digoxin levels and cause additive slowing of the heart rate and atrioventricular (AV) conduction. If either is newly prescribed alongside digoxin, monitor closely for bradycardia and signs of toxicity.⁴
• Loop diuretics (furosemide) and thiazide diuretics cause hypokalaemia, which potentiates digoxin toxicity. Many patients on digoxin are also on diuretics. Confirm that potassium monitoring is current or has been arranged by the prescriber, and act on any reported falls promptly.⁴
• Spironolactone inhibits the renal tubular secretion of digoxin and raises levels. A dose change in spironolactone should prompt vigilance for toxicity signs.⁴
• Macrolide antibiotics (erythromycin, clarithromycin) can increase digoxin levels in some patients by eradicating gut bacteria that normally inactivate digoxin before absorption. This effect is unpredictable. Do not automatically withhold supply if the antibiotic is clinically urgent: contact the prescriber or pharmacist to review the interaction, and counsel the patient to report any toxicity symptoms promptly.⁴
• St John's Wort induces P-glycoprotein and can reduce digoxin concentrations, potentially reducing efficacy. Check for herbal medicines and supplements at every dispense.⁴
• Tablet and oral liquid (elixir) formulations of digoxin are not directly interchangeable: strengths differ and bioavailability varies. Confirm the formulation on every prescription and record it on the pharmacy medication record.⁴
• Do not interpret a serum digoxin level in isolation. Always assess it alongside symptoms, renal function, potassium, magnesium, thyroid status, sample timing, and any new interacting medicines before deciding on action.²
• If a serum digoxin level is being checked after a dose change, sampling should take place around 7 days after the change, or once steady state is reached, according to local or prescriber guidance.²

First dispense script

🔄 Repeat Dispense Screen

Mandatory documentation

• Record the dose and formulation dispensed on every occasion. Note any dose changes and the reason.
• Confirm that electrolyte, renal function, and thyroid monitoring is current or has been arranged by the prescriber. Document any interventions made if monitoring appears overdue.
• Note any newly started or recently stopped interacting medicines.

Ongoing clinical checks

• Urea and electrolytes (including potassium) and renal function: at least annually, and more frequently in elderly patients, those with renal impairment, or those on diuretics. Confirm monitoring is current or has been arranged by the prescriber. Consider magnesium monitoring in patients at higher risk of deficiency, including those on long-term proton pump inhibitors.^2,3
• Thyroid function: annually. Thyroid status affects digoxin requirements and can change over time.⁴
• Serum digoxin level: not required routinely. Check if toxicity is suspected, renal function has deteriorated, a new interacting medicine has been started, or around 7 days after any dose change. Always interpret the result alongside symptoms, renal function, electrolytes, sample timing, and current interacting medicines.²
• Check for any newly prescribed interacting medicines, especially amiodarone, verapamil, diltiazem, spironolactone, diuretics, and macrolide antibiotics.⁴

Ask the patient at the counter

• "Have you noticed any nausea, loss of appetite, vomiting, diarrhoea, or changes in your vision, particularly blurring or seeing yellow or green around lights?"
• "Has your heart felt very slow, or have you noticed an irregular heartbeat or new dizziness?"
• "Have you started any new medicines or had any change to your existing medicines recently?"
• "Have you been unwell with vomiting, diarrhoea, or poor fluid intake recently? These can raise digoxin levels."

Lifestyle and surgical alerts

• Dehydration, vomiting, and diarrhoea raise digoxin levels by reducing renal clearance. During any such illness, patients should contact their prescriber promptly rather than waiting for the next scheduled review.
• Any significant change in kidney function, including following acute illness or surgery, may require a digoxin dose review and level check.
• Patients should not stop digoxin suddenly without prescriber advice. Loss of rate control may follow abrupt discontinuation in atrial fibrillation.
• Advise patients to keep an up-to-date medicines list or carry a digoxin alert card so that any treating clinician is aware of the interaction risk and monitoring requirements.

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