Final answer:
The most appropriate action for the nurse to take initially would be to check the patient's serum creatinine level report. Monitoring kidney function is crucial in determining the appropriate dosage of digoxin.
Step-by-step explanation:
In this scenario, the most appropriate action for the nurse to take initially would be option d) Check the patient's serum creatinine level report. Digoxin is primarily excreted by the kidneys, so monitoring the patient's kidney function is crucial in determining the appropriate dosage of the drug. The nurse needs to ensure that the patient's kidney function is within normal limits to prevent digoxin toxicity.