Compared to epidural, intrathecal administration of lipophilic opioids provides which characteristic?

Compared to epidural, intrathecal administration of lipophilic opioids provides which characteristic?

• A. Intrathecal administration increases rostral spread.
• B. Epidural administration avoids rostral spread.
• C. Intrathecal administration avoids rostral spread, reducing the risk of delayed respiratory depression.
• D. There is no difference between routes.

Answer: (C)

Rostral spread within the CSF is the factor being tested. Lipophilic opioids given directly into the intrathecal space rapidly partition into nearby neural tissue and are quickly absorbed into the blood, so they don’t stay in the CSF to diffuse upward toward the brainstem. This limits cephalad (rostral) distribution and lowers the risk of delayed respiratory depression from brainstem exposure. In contrast, administering in the epidural space allows more opportunity for diffusion into the CSF and upward spread, which can increase the likelihood of higher-level exposure if the drug reaches the brainstem, potentially delaying respiration. Thus, intrathecal lipophilic opioids have limited rostral spread and a lower risk of delayed respiratory depression compared with epidural administration.

Rostral spread within the CSF is the factor being tested. Lipophilic opioids given directly into the intrathecal space rapidly partition into nearby neural tissue and are quickly absorbed into the blood, so they don’t stay in the CSF to diffuse upward toward the brainstem. This limits cephalad (rostral) distribution and lowers the risk of delayed respiratory depression from brainstem exposure.

In contrast, administering in the epidural space allows more opportunity for diffusion into the CSF and upward spread, which can increase the likelihood of higher-level exposure if the drug reaches the brainstem, potentially delaying respiration.

Thus, intrathecal lipophilic opioids have limited rostral spread and a lower risk of delayed respiratory depression compared with epidural administration.