What is the duration of action (DOA) of methadone?

What is the duration of action (DOA) of methadone?

• A. 8-12 hours
• B. 4-6 hours
• C. 1-3 hours
• D. 24-36 hours

Answer: (B)

The duration of action measures how long the drug’s analgesic effects last after a dose. For methadone, the analgesic effect typically lasts about 4–6 hours. This can be confusing because methadone has a very long elimination half-life (roughly 24–36 hours), which means the drug stays in the body for a long time and can accumulate with repeated dosing. However, the short-term analgesic effect is governed by how long the plasma concentration stays above the level needed to produce pain relief, which is about 4–6 hours. Clinically, this long half-life explains why methadone can accumulate and why dosing intervals must be managed carefully to avoid prolonged sedation or respiratory depression, even though the immediate analgesic effect is shorter.

The duration of action measures how long the drug’s analgesic effects last after a dose. For methadone, the analgesic effect typically lasts about 4–6 hours. This can be confusing because methadone has a very long elimination half-life (roughly 24–36 hours), which means the drug stays in the body for a long time and can accumulate with repeated dosing. However, the short-term analgesic effect is governed by how long the plasma concentration stays above the level needed to produce pain relief, which is about 4–6 hours. Clinically, this long half-life explains why methadone can accumulate and why dosing intervals must be managed carefully to avoid prolonged sedation or respiratory depression, even though the immediate analgesic effect is shorter.