What is the approximate half-life of digoxin?

What is the approximate half-life of digoxin?

• A. Half-life is about 12 hours
• B. Therapeutic index is extremely high
• C. Half-life is about 1.7 days
• D. Toxicity never occurs

Answer: (C)

Half-life is the time it takes for the drug’s plasma concentration to fall by half, which reflects how long the drug stays in the body. Digoxin is cleared mainly by the kidneys, so in adults with normal renal function its half-life is about 36–48 hours, roughly 1.5–2 days. Saying it is about 1.7 days fits this typical range. This long half-life means dosing changes affect levels slowly, and renal impairment can lengthen the half-life even more, requiring dose adjustments. It also explains why digoxin has a narrow therapeutic index—small shifts in dose or kidney function can push levels into toxicity. Why the other ideas don’t fit: 12 hours would imply much faster clearance than digoxin usually has; saying the therapeutic index is extremely high contradicts digoxin’s known narrow therapeutic window and need for careful monitoring; and toxicity can and does occur, especially with renal impairment, electrolyte disturbances, or drug interactions, so it is not true that toxicity never occurs. So, the approximate half-life is about 1.7 days.

Half-life is the time it takes for the drug’s plasma concentration to fall by half, which reflects how long the drug stays in the body. Digoxin is cleared mainly by the kidneys, so in adults with normal renal function its half-life is about 36–48 hours, roughly 1.5–2 days. Saying it is about 1.7 days fits this typical range.

This long half-life means dosing changes affect levels slowly, and renal impairment can lengthen the half-life even more, requiring dose adjustments. It also explains why digoxin has a narrow therapeutic index—small shifts in dose or kidney function can push levels into toxicity.

Why the other ideas don’t fit: 12 hours would imply much faster clearance than digoxin usually has; saying the therapeutic index is extremely high contradicts digoxin’s known narrow therapeutic window and need for careful monitoring; and toxicity can and does occur, especially with renal impairment, electrolyte disturbances, or drug interactions, so it is not true that toxicity never occurs.

So, the approximate half-life is about 1.7 days.