5 Cardiac Glycosides
Learn how digoxin is used to control ventricular rate and manage some heart-failure symptoms, and how to recognize and reduce risks related to toxicity, monitoring, kidney function, electrolytes, and drug interactions.
Therapeutic uses
may be used to control the ventricular rate in chronic atrial fibrillation by slowing conduction through the . Its role in this setting is rate control; the material does not describe it as converting atrial fibrillation to a normal rhythm.
In some adults with heart failure, may improve symptoms and reduce heart-failure-related hospitalizations. It has not been shown to reduce mortality.
Recognizing possible toxicity
has a narrow safety margin, so its clinical effects and potential adverse effects require attention. Possible toxicity may present with gastrointestinal symptoms such as nausea or poor appetite, visual changes such as yellow-tinted vision, bradycardia, or other rhythm and conduction disturbances.
These signs call for prompt assessment and contact with the prescribing clinician. Symptoms and clinical findings matter: toxicity can occur even when a measured is not above 2 ng/mL, so symptoms do not prove that the level has crossed that threshold.
Factors that affect toxicity risk
Assess clinical response, pulse and rhythm, , and electrolytes when monitoring treatment. is primarily excreted by the kidneys. If worsens, clearance can slow and may accumulate, increasing toxicity risk; clinicians consider kidney function when selecting and reassessing the dose.
Low potassium () and low magnesium (hypomagnesemia) can predispose a patient to toxicity. For example, a patient taking with a loop diuretic may be at increased risk if the diuretic contributes to a low potassium level.
Interpreting levels
A blood sample for a should generally be collected at least 6 hours after the last dose, or just before the next dose. An earlier sample can be misleading because needs time to distribute into tissues.
Interpret a level alongside symptoms, treatment response, kidney function, and electrolytes. Do not change a dose based on an isolated level alone.
Drug interactions and combined effects
Medication changes should prompt review of the treatment plan and appropriate monitoring. can increase concentrations, so the prescriber may need to adjust the dose and monitor levels. Other medicines can also affect levels or heart-rate conduction.
taken with a beta blocker can have an additive effect on AV-node conduction. Monitor the clinical response for an excessively slow heart rate or conduction problems, including heart block. Potassium-wasting diuretics can also increase toxicity risk indirectly by lowering potassium.