Intravenous diclofenac sodium. Does its administration before operation suppress postoperative pain? Intravenous diclofenac sodium was evaluated in a double-blind randomised trial relative to intramuscular diclofenac, intravenous fentanyl, and intramuscular placebo in 160 patients undergoing extraction of impacted lower third molar teeth. The test drug was administered before operation in an attempt to alleviate postoperative pain. A 10-cm visual analogue scale was used to assess pain at 30 minutes and one day after surgery, if the patients stayed overnight. Patients who received intravenous diclofenac had significantly less pain than the other groups 30 minutes after operation. They also had significantly less pain one day after surgery than the placebo or opioid groups, but not less than the intramuscular diclofenac group. Capillary bleeding time, in comparison with placebo, was significantly prolonged after the use of intramuscular diclofenac, and a similar but nonsignificant trend was observed in the intravenous diclofenac group. No problems were encountered with excessive bleeding in any group. 