[Intramuscular versus rectal diclofenac associated with low dose spinal morphine for post-cesarean analgesia.]

Diclofenac has been used in combination with spinal opioids to control postoperative pain; however, the best regimen of its administration is not known. This study evaluated the quality of postoperative analgesia of different regimens of diclofenac administration, in patients submitted to Cesarean section under spinal anesthesia with bupivacaine and morphine.

After the end of surgery, patients were randomly allocated into three groups that received diclofenac as follows: G50VR(n=62), 50 mg rectally; G50IM(n=62), 50 mg intramuscularly and G75IM (n=62), 75 mg intramuscularly. Pain was evaluated with a 0-10 cm visual analog scale (VAS) every 30 minutes for six hours and rescue intravenous (iv) meperidine was administered whenever VAS >/= 3 cm.

In the interval between 30 and 150 min after diclofenac administration, mean pain scores in G50VR (0.9 +/- 1.4; 1.4 +/- 1.4; 1.3 +/- 1.5; 1.3 +/- 1.2 and 1.5 +/- 3.3 cm) were higher as compared to G50IM (0.4 +/- 0.8; 0.5 +/- 0.8; 0.7 +/- 1.0; 0.7 +/- 1.1 and 0.7 +/- 1.1cm) and G75IM (0.4 +/- 0.8; 0.7 +/- 1.3; 0.7 +/- 1.1; 0.8 +/- 1.2 and 0.7 +/- 1.0 cm). The need for rescue meperidine (43.5%) and total meperidine consumption (21.3 +/- 28.9 mg) were higher in G50VR as compared to G50IM (21% and 8.2 +/- 18.2 mg) and G75IM (19.4% and 6.8 +/- 16.7 mg) respectively.

When associated with low doses of spinal morphine, intramuscular diclofenac offers better postoperative analgesia than the rectal route. Additionally, a ceiling effect is probably present for this drug, as no advantages were observed with doses larger than 50 mg intramuscularly.