Intrathecal opioids require about what fraction of IV/epidural doses?

Intrathecal opioids require about what fraction of IV/epidural doses?

• A. Equal to IV dose
• B. One-tenth
• C. One-half
• D. Ten times

Answer: (B)

Intrathecal opioids are far more potent per milligram than systemic or epidural doses because the drug is delivered directly into the cerebrospinal fluid right at the site of the spinal receptors. This proximity to the mu-opioid receptors in the dorsal horn means a much smaller amount is needed to achieve meaningful analgesia, compared with IV or epidural administration where the drug must distribute systemically and diffuse across barriers to reach those receptors. For this reason, the general rule used in practice is that intrathecal doses are about one-tenth of IV or epidural doses. Keep in mind that exact amounts depend on the specific opioid and clinical context, and intrathecal administration can carry risks such as delayed respiratory depression and other opioid-related side effects, so careful monitoring is essential.

Intrathecal opioids are far more potent per milligram than systemic or epidural doses because the drug is delivered directly into the cerebrospinal fluid right at the site of the spinal receptors. This proximity to the mu-opioid receptors in the dorsal horn means a much smaller amount is needed to achieve meaningful analgesia, compared with IV or epidural administration where the drug must distribute systemically and diffuse across barriers to reach those receptors. For this reason, the general rule used in practice is that intrathecal doses are about one-tenth of IV or epidural doses. Keep in mind that exact amounts depend on the specific opioid and clinical context, and intrathecal administration can carry risks such as delayed respiratory depression and other opioid-related side effects, so careful monitoring is essential.