A client has received digoxin 0.25 mg po daily for 2 weeks. Which of the following digoxin levels indicates toxicity?

The accepted therapeutic serum range for digoxin is 0.5 to 2.0 ng/mL. A digoxin level of 3.0 ng/mL is significantly above this range and is considered toxic. Digoxin has a narrow therapeutic index, meaning the dose that is effective is close to the dose that is toxic. Clinical manifestations of toxicity include gastrointestinal symptoms (nausea, vomiting, anorexia), neurological complaints (fatigue, confusion, visual disturbances like yellow-green halos), and life-threatening cardiac dysrhythmias (e.g., bradycardia, heart block). This level requires immediate intervention, including withholding the medication and notifying the provider.

A. 0.5 ng/mL: This level is at the lower end of the therapeutic range (0.5-2.0 ng/mL) and is not indicative of toxicity.

B. 1.0 ng/mL: This level is well within the accepted therapeutic range (0.5-2.0 ng/mL) and represents an effective, non-toxic concentration.

C. 2.0 ng/mL: This level is at the upper limit of the therapeutic range. While it warrants close monitoring, it is not definitively toxic.

1. Shah, R., & Yella, S. (2023). Digoxin. In StatPearls. StatPearls Publishing. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK556025/. In the "Monitoring" section, the article states, "The generally accepted therapeutic range for digoxin is 0.5 to 2 ng/mL...Toxicity is most often associated with digoxin levels over 2.0 ng/mL."

2. Ren, F., Wang, Z., & Wang, J. (2021). Digoxin Toxicity. Cardiovascular Toxicology, 21(1), 1-10. https://doi.org/10.1007/s12012-020-09603-7. This peer-reviewed article discusses that "serum digoxin concentrations (SDCs) >2.0 ng/mL are generally considered toxic" (p. 2).

3. Johns Hopkins University School of Nursing. (n.d.). Cardiovascular Medications. Courseware materials for NR.110.501 Advanced Pharmacology. The curriculum specifies the therapeutic drug monitoring parameters for digoxin, citing the 0.5-2.0 ng/mL range and defining toxicity as serum concentrations exceeding 2.0 ng/mL.