Therapeutic plasma level of digoxin –
**Core Concept**
Digoxin is a cardiac glycoside used in the treatment of heart failure and atrial fibrillation. Its therapeutic plasma level is crucial in determining its efficacy and safety. The therapeutic plasma level of digoxin is typically between 0.5-1.5 ng/mL.
**Why the Correct Answer is Right**
The therapeutic plasma level of digoxin is determined by its binding to digoxin-specific receptors in the heart and other tissues. Digoxin inhibits the sodium-potassium ATPase pump, leading to increased intracellular sodium and calcium levels, which in turn increases the contractility of the heart muscle. The optimal plasma level of digoxin is achieved when the drug's effect on the heart is balanced with its potential toxicity. The therapeutic window of digoxin is narrow, and plasma levels above 2 ng/mL can lead to toxicity.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a valid therapeutic range for digoxin. While digoxin levels above 2 ng/mL are toxic, this option does not provide a safe or effective range.
**Option B:** This option is incorrect because it is too high and suggests a toxic level of digoxin. Plasma levels above 2 ng/mL can lead to digoxin toxicity, which can manifest as nausea, vomiting, confusion, and cardiac arrhythmias.
**Option C:** This option is incorrect because it is too low and suggests a subtherapeutic level of digoxin. Plasma levels below 0.5 ng/mL may not provide adequate clinical benefit for patients with heart failure or atrial fibrillation.
**Clinical Pearl / High-Yield Fact**
The therapeutic plasma level of digoxin is crucial in determining its efficacy and safety. Clinicians should carefully monitor digoxin levels in patients, especially those with kidney or liver disease, to avoid toxicity.
**Correct Answer:** Correct Answer: D