Is a digoxin (digitalis glycoside) blood level of 0.70 ng/mL within the therapeutic range?

Digoxin Level of 0.70 ng/mL: Therapeutic Range Assessment

A digoxin blood level of 0.70 ng/mL is within the therapeutic range and represents an optimal target concentration for most patients with heart failure.

Therapeutic Range Context

• The American Heart Association recommends maintaining digoxin serum concentrations between 0.5 to 1.0 ng/mL for optimal clinical benefit with minimal risk of toxicity 1
• Your level of 0.70 ng/mL falls comfortably in the middle of this recommended range 1
• The European Society of Cardiology suggests a slightly wider range of 0.6 to 1.2 ng/mL for chronic therapy in patients with normal renal function, which also includes your level 1

Evidence Supporting Lower Therapeutic Targets

• Retrospective analyses demonstrate that prevention of worsening heart failure at lower concentrations (0.5 to 0.9 ng/mL) was as effective as higher concentrations 1
• Risk-adjusted mortality actually increased as plasma concentrations exceeded 1.0 ng/mL in the Digitalis Investigation Group trial 1
• The FDA label indicates that about two-thirds of adequately digitalized adults (without toxicity) have serum concentrations ranging from 0.8 to 2.0 ng/mL, though clinical benefits can occur even below this range 2

Clinical Implications at This Level

• At 0.70 ng/mL, the patient is at minimal risk for toxicity while maintaining therapeutic efficacy 1
• This level is particularly appropriate for patients with risk factors including advanced age (>70 years), renal impairment, low lean body mass, or those on interacting medications 1
• No dose adjustment is needed unless clinical response is inadequate or signs of toxicity emerge 1

Important Monitoring Caveats

• Toxicity can occur even within the therapeutic range (0.5-1.2 ng/mL) in the presence of hypokalemia, hypomagnesemia, hypothyroidism, or drug interactions 3, 1
• The serum concentration should always be interpreted in the overall clinical context, not as an isolated measurement 2
• Monitor for clinical manifestations of toxicity including cardiac arrhythmias (especially ventricular tachycardia, AV block), gastrointestinal symptoms (nausea, vomiting, anorexia), and neurological symptoms (confusion, visual disturbances) 3

Timing of Sample Collection

• Sampling should be done just before the next scheduled dose, or at least 6 to 8 hours after the last dose to allow adequate time for equilibration between serum and tissue 2
• On once-daily dosing, concentrations will be 10-25% lower when sampled at 24 versus 8 hours, depending on renal function 2