What is the approximate half-life of methadone?

What is the approximate half-life of methadone?

• A. 2-4 days
• B. 15-30 hours
• C. 6-12 hours
• D. 6-8 hours

Answer: (B)

Methadone has a long elimination half-life compared with many opioids, due to its high lipophilicity and extensive tissue distribution. In adults, the typical terminal half-life is on the order of about a day, often quoted around 24–36 hours. Among common approximate ranges, 15–30 hours best matches this long but not extremely prolonged elimination profile, making it the closest fit to the usual teaching. Shorter ranges (6–12 or 6–8 hours) fit shorter-acting opioids, while a range like 2–4 days would imply a longer half-life than is generally cited for standard methadone pharmacokinetics. This long half-life also explains why methadone can accumulate with repeated dosing and why careful titration is important.

Methadone has a long elimination half-life compared with many opioids, due to its high lipophilicity and extensive tissue distribution. In adults, the typical terminal half-life is on the order of about a day, often quoted around 24–36 hours. Among common approximate ranges, 15–30 hours best matches this long but not extremely prolonged elimination profile, making it the closest fit to the usual teaching. Shorter ranges (6–12 or 6–8 hours) fit shorter-acting opioids, while a range like 2–4 days would imply a longer half-life than is generally cited for standard methadone pharmacokinetics. This long half-life also explains why methadone can accumulate with repeated dosing and why careful titration is important.