NSAIDs have an important central antinociceptive activity, parallel and concomitant with their peripheral anti-inflammatory effects. The nociceptive flexion reflex is an experimental model for neurophysiological studies of pain, providing a sensitive evaluation of the nociceptive threshold during various pharmacological treatments in humans. In this research, the analgesic, antinociceptive effects of rofecoxib and nimesulide were compared in a group of normal subjects, using the inhibition of the nociceptive flexion reflex threshold as marker of analgesic activity. Twelve normal male subjects (37.2±8.05 years old) were enrolled in a double-blind, three-treatment, three-period crossover design, comparing 50 mg rofecoxib and 100 mg nimesulide vs. placebo. To prevent carryover effects between treatments, a 72-hour wash-out interval was allowed between drug administrations. Nociceptive flexion reflex threshold from the caput brevis of biceps femoris caput brevis elicited by sural nerve electrical stimulation was studied before drug administration and during a 60 min observation. Nociceptive flexion reflex threshold, expressed in mAmp needed to elicit the response, was recorded every 5 min for the first 30 min and then every 10 min. Nociceptive flexion reflex rate of changes in mA/min was also calculated to define the speed of inhibition during the first 5 min and 10 min after drug administration. Rofecoxib has a better inhibitory effect on the nociceptive flexion reflex than does nimesulide with faster onset of action, a maximal inhibitory effect between 20 min and 30 min. Both drugs provided durable inhibition throughout the 60 min of recording, although nociceptive flexion reflex inhibition brought about by rofecoxib was on average 33% higher than that obtained after nimesulide.
- Nociceptive flexion reflex
ASJC Scopus subject areas
- Clinical Neurology
- Anesthesiology and Pain Medicine