Final answer:
Digoxin overdose is characterized by a toxic serum level greater than 2.1 ng/ml, can cause long PR intervals and xanthopsia, but does not cause a long QT interval.
Step-by-step explanation:
The question pertains to the effects and symptoms of digoxin overdose/toxicity. A serum level greater than 2.1 ng/ml is considered toxic (> 2.1 ng/ml is toxic). Digoxin toxicity can manifest various symptoms including long PR intervals, not QT intervals (Causes a long PR interval), and can induce xanthopsia, which is commonly referred to as "yellow vision" (Causes xanthopsia). Moreover, digoxin toxicity is also associated with arrhythmias such as bigeminy, but it does not cause a long QT interval which is typically linked to other conditions or medications (Causes a long QT interval and bigeminy).