Is the sulphonamide radical in the celecoxib molecule essential for its analgesic activity?

In a model of peripherally induced inflammatory pain in rats, selective inhibitors of cyclooxygenase (COX)-2 raised nociceptive thresholds above basal values, an effect referred to as "hypoalgesia". However other, non-selective, inhibitors of COX (indomethacin, piroxicam) or a selective inhibitor of COX-1 did not induce hypoalgesia in this model, implying that COX inhibition was not causally related to the hypoalgesic effect. Here, we have assessed whether other COX-2 inhibitors or other sulphonamides, apart from celecoxib could exhibit hypoalgesia in our model of inflammatory pain.