Background: This study was conducted to avoid the pain of an intramuscular injection of diclofenac after a cesarean section, by modifying it to an intravenous infusion by diluting it with 5% dextrose in 100 mL of water.

Objective: The aim of this study was to determine the efficacy of a single-dose modified diclofenac being given intravenously, instead of intramuscularly, for pain relief after a cesarean section.

Study design: A double-blind, randomized controlled trial was conducted.

Participants: We enrolled 30 patients who underwent cesarean sections with Pfannenstiel skin incision.

Methods: All patients received 2.2–2.5 mL of 0.5% bupivacaine with 0.2 mg morphine for spinal anesthesia. The participants were equally and randomly allocated to two groups to receive intravenous diclofenac or placebo at 12 hours postoperatively. Both groups received the same regimen for postoperative pain control.

Main outcome measurements: The severity of postoperative pain was measured directly using a verbal numerical rating scale (0–10) and a pain-relief scale (1–4), and indirectly from the amount of tramadol used.

Results: The characteristics of the two groups of patients were similar. The mean postoperative pain relief at 24 hours in the study group was better than that in the control group (3.14 ± 0.66 vs. 2.13 ± 0.99; p < 0.05). The severity of postoperative pain at 24 hours and the amount of tramadol used were not different between groups.

Conclusion: Intramuscular diclofenac (75 mg), modified by diluting it with 5% dextrose in 100 mL of water, for intravenous administration in combination with spinal morphine (0.2 mg) provided good analgesia after a cesarean section within 24 hours when assessed by the pain-relief scale; however, the mean pain intensity was not different.