Cardiovascular Drugs and Medications Q 56
Blurred vision or halos are signs of:
A. Subtherapeutic digoxin levels.
B. Digoxin toxicity.
C. Nothing related to digoxin.
D. Corneal side effects of digoxin.
Correct Answer: B. Digoxin toxicity.
Halos is a hallmark sign of digoxin toxicity. Digoxin exhibits its therapeutic and toxic effects by poisoning the sodium-potassium ATPase. The subsequent increase in intracellular sodium leads to increased intracellular calcium by decreasing calcium expulsion through the sodium-calcium, cation exchanger. A, C and D are incorrect because subtherapeutic digoxin levels have no such effects.
Option A: Digoxin’s therapeutic half-life is between 30 to 40 hours, but this may change in overdose. Digoxin excretion is primarily renal, and for this reason, patients with poor or worsening renal function, such as patients who are elderly or have CKD, are more likely to develop toxicity.
Option C: Digoxin levels start to plateau at 6 hours, which is after tissue redistribution has occurred; earlier levels may thus be misleadingly high. Cardiovascular toxicity may have delayed manifestation of up to 8 to 12 hours post-ingestion.
Option D: Visual side effects might include color changes, also known as xanthopsia. But yellow or green-tinted vision is usually associated with digoxin toxicity. Patients may also highlight blurry vision or photopsia.