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Dangerous Drug Interaction: Digoxin-Verapamil

digoxin (Lanoxin) verapamil (Calan, Calan SR, Covera-HS, Isoptin, Isoptin SR, Verelan, Verelan PM)
Brand names appear in parentheses above and are trademarks of their respective manufacturers/owners.

Impact: Potential for digoxin toxicity.1

Mechanism of Interaction: Serum digoxin concentration rise by 60-75% due to decreased renal tubular secretion and nonrenal clearance mechanisms.12,13 Biliary clearance of digoxin is reduced by 42-43% when administered with verapamil.14,15 Additionally, there appears to be a synergistic effect of slowing impulse conduction and muscle contractility, leading to bradycardia and possible heart block.8,16

Alternatives to Patient Management: Monitor heart rate and EKG-PR interval. Evaluate selection of verapamil and digoxin. If patient has CHF, note that verapamil has not proven any benefit in mortality or morbidity; furthermore, digoxin offers no additional benefit in mortality, but does improve symptomatology. Digoxin therapy should be cautiously started in patients with hypokalemia, hypomagnesemia or hypothyroidism due to the potential for adverse drug reactions at lower digoxin levels.10,11

Monitoring/Precautions:

  1. Maintain digoxin level below 2ng/mL (2.6nmol/L).12
  2. Monitor for signs and symptoms of digoxin toxicity (abdominal pain, anorexia, bizarre mental symptoms in the elderly, blurred vision, bradycardia, confusion, delirium, depression, diarrhea, disorientation, drowsiness, fatigue, hallucinations, halos around lights, visual acuity, mydriasis nausea, neuralgia, nightmares, personality changes, photophobia, restlessness, vertigo, vomiting, and weakness).
  3. Monitor heart rate for bradycardia and EKG-PR interval.
  4. Monitor calcium, magnesium and potassium levels.

References: Follow this link for a complete list of references.

The above information serves only as a guide for use by qualified medical practitioners in understanding, handling and avoiding frequent and potentially dangerous drug interactions that occur in long-term care. This presentation is not intended to instruct a practitioner how to treat any medical condition, nor is it intended to replace a practitioner's best clinical judgment. AMDA expressly disclaims responsibility and liability for any adverse effects, damages or other consequences resulting from the use of any of the information contained in this presentation.

 
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