Digitalis (Digoxin)
A cardiac glycoside that increases contractility and slows heart rate
Definition
Digoxin is a cardiac glycoside derived from the foxglove plant (Digitalis lanata). It has a positive inotropic effect (increases force of contraction) and a negative chronotropic effect (slows heart rate). Used in heart failure and atrial fibrillation with rapid ventricular rate.
Therapeutic Range
0.5 to 2.0 ng/mL (narrow therapeutic window; toxicity common).
Toxicity Signs
- Anorexia, nausea, vomiting
- Visual disturbances (yellow-green halos, blurred vision)
- Bradycardia, heart block, arrhythmias
- Confusion, fatigue
Risk Factors for Toxicity
Hypokalemia (most critical), hypomagnesemia, hypercalcemia, renal impairment, advanced age, dehydration, drug interactions (amiodarone, verapamil).
Nursing Administration
Check apical pulse for 1 full minute before each dose. HOLD if adults less than 60, infants less than 90, children less than 70 bpm. Monitor potassium and drug level. Teach patients to report symptoms immediately, for toxicity, administer Digoxin Immune Fab (Digibind).
NCLEX Relevance
Classic scenario: low potassium + digoxin = toxicity. Yellow-green halos are the visual hallmark.