Intrathecal Morphine 75 Mcg vs 100 Mcg for Cesarean Analgesia

Key Takeaways

• The trial compared 75 mcg and 100 mcg intrathecal morphine during spinal anesthesia for cesarean delivery.
• Analgesic outcomes included postoperative pain, rescue analgesic use, and time to first analgesic request.
• Common opioid-related adverse effects were also assessed in the dose comparison.

The comparison centered on postoperative recovery after cesarean birth, assessing pain control and adverse-effect outcomes across the two dose groups.

Investigators conducted the randomized double-blind trial in patients undergoing cesarean delivery under spinal anesthesia, using a direct comparison between two intrathecal morphine doses. The study question remained narrowly focused on post-cesarean analgesia within that procedural setting.

The efficacy analysis centered on postoperative analgesic outcomes predefined for the two dose groups. At the primary 12-hour endpoint, pain intensity did not differ significantly, with median VAS scores of 0.0 in the 75 mcg group and 1.0 in the 100 mcg group (p = 0.224). No significant differences were observed at 4, 8, or 24 hours. Non-opioid rescue analgesia was required in 41.7% of patients in the 75 mcg group and 37.5% in the 100 mcg group (p = 0.509), and no patients required opioid rescue analgesia.

Safety assessment accompanied the analgesic comparison, with common opioid-related adverse effects evaluated in the 75 mcg and 100 mcg groups. Adverse effects were similar between groups, including pruritus (25.0% vs 20.8%, p = 0.442), nausea (16.7% vs 8.3%, p = 0.051), and vomiting (4.2% vs 8.3%, p = 0.182).

Overall, a 75 mcg dose of intrathecal morphine was associated with comparable postoperative analgesia to 100 mcg, with no statistically significant differences in pain scores or adverse effects. However, the study was not designed as a noninferiority or equivalence trial, and these findings should not be interpreted as definitive evidence of equivalence between doses.