Users

Digoxin Monitoring

Affected Drug

• C01AA05 Digoxin

Baseline

Baseline: SCr/BUN, electrolytes, recent ECG

Follow-up

Follow-up: SCr/BUN, electrolytes 1-2 weeks following addition of any drugs affecting renal function or electrolytes (ex. Diuretics, ACE inhibitors/ARBs, potassium supplements, etc.). Serum Levels: Routine measurements not recommended. If indicated, measure trough at least 8 hours following dose. Serum levels may be indicated in the following circumstances: 1. Suspected toxicity (especially if toxicity confounded by other agents such as beta-blockers) 2. Significant changes in renal function (consider pre-emptive dose reduction) 3. Addition of drug with significant interaction potential (consider pre-emptive dose reduction) 4. Assessment of compliance Target serum levels (if measured): CHF: 0.6-1.0 nmol/L Atrial Fibrillation: No target level, dose should be adjusted to target heart rate

Important Interactions

• Drugs: C01BD01 Amiodarone
  Interaction Increased risk of digoxin toxicity (reduce dose by 50%)
• Drugs: C03CA01 Furosemide
  Interaction May cause hypokalemia and increase risk of toxicity (measure electrolytes and renal function during diuretic therapy)
• Drugs: J01FA01 Erythromycin
  Interaction increased digoxin levels and increases risk of digoxin toxicity
• Drugs: J01FA09 Clarithromycin
  Interaction increased digoxin levels and increases risk of digoxin toxicity
• Drugs: C03BA04 Chlortalidone
  Interaction May cause hypokalemia and increase risk of toxicity (measure electrolytes and renal function during diuretic therapy)
• Drugs: diuretics
  Interaction May cause hypokalemia and increase risk of toxicity (measure electrolytes and renal function during diuretic therapy)
• Drugs: C03AA03 Hydrochlorothiazide
  Interaction May cause hypokalemia and increase risk of toxicity (measure electrolytes and renal function during diuretic therapy)
• Drugs: J02AB02 Ketoconazole
  Interaction Increases risk of digoxin toxicity (reduce dose by 50%)
• Drugs: J02AC02 Itraconazole
  Interaction Increases risk of digoxin toxicity (reduce dose by 50%)
• Drugs: C01BC03 Propafenone
  Interaction Increases risk of digoxin toxicity (reduce dose by 50%)
• Drugs: C01BA01 Quinidine
  Interaction Increases risk of digoxin toxicity (reduce dose by 50%)
• Drugs: C08DA01 Verapamil
  Interaction Increases risk of digoxin toxicity (reduce dose by 50%)

Details

Conditions	System	Monitoring		ADE	Incidence	Recommendation
		Baseline	Follow-up
	CNS	Physical exam	Physical exam	visual disturbances	Generally sign of toxicity	Measure serum level and hold drug
				fatigue, weakness		Consider ↓ dose
	Cardiac	ECG, physical exam	Physical exam	ventricular arrhythmia, 1st 2nd 3rd degree av block, sinus bradycardia	variable	↓ dose or d/c. If evidence of severe toxicity refer to Emergency for drug levels and possible antidote
	Metabolic	Electrolytes	Electrolytes if electrolyte affecting drug added	hyperkalemia with chronic or acute overdose. hypokalemia precipitates toxicity	variable	treat as per electrolyte abn
	Renal	BUN/SCr	BUN/SCr if renally toxic drug added	not nephrotoxic, but ↑ risk of toxicity with ↓ renal function	variable	Hold drug during acute renal failure. ↓ dose with ↓ renal function
	Gastrointestinal	Physical exam	Physical exam	nausea, anorexia, abdominal pain		Nausea and anorexia may be sign of chronic toxicity – consider ↓ dose

References

• Gray J, editor. Therapeutic Choices, 5th edition. Ottawa: The Canadian Pharmacists Association; 2007.
• DiPiro JT et al, editors. Pharmacotherapy A Pathophysiologic Approach, 6th edition. McGraw Hill; 2005.
• Jessup M et al. 2009 focused update incorporated into the ACC/AHA 2005 guidelines for the diagnosis and management of heart failure in adults. J Am Coll Cardiol 2009;53:e1-e90.