EFFECTS OF FLURBIPROFEN ENANTIOMERS ON PAIN-RELATED CHEMO-SOMATOSENSORY EVOKED-POTENTIALS IN HUMAN-SUBJECTS

1 The aim of the study was to investigate the analgesic effects of flu rbiprofen enantiomers using an experimental pain model based on both c hemo-somatosensory event-related potentials (CSSERP) and subjective pa in ratings. 2 Healthy female volunteers (n = 16, age 23-36 years) part icipated in a placebo-controlled, randomised, double-blind, four-way c rossover study. Single doses of (S)-flurbiprofen (50 mg), (R)-flurbipr ofen (50 and 100 mg) and placebo were administered orally. Measurement s were taken before and 2 h after administration of the medications. D uring each measurement, 32 painful stimuli of gaseous carbon dioxide ( 200 ms duration, interval approximately 30 s) of two concentrations (6 0 and 65% CO2 v/v) were applied to the right nostril. EEG was recorded from five positions and CSSERP were obtained in response to the painf ul CO, stimuli. Additionally, subjects rated the perceived intensity o f the painful stimuli by means of a visual analogue scale (VAS). 3 The CSSERP-amplitude P2, a measure of analgesic effect, decreased after a dministration of both (R)- and (S)-flurbiprofen, while it increased af ter placebo. This was statistically significant at recording positions C4 (P < 0.01) and Fz (P < 0.05). The analgesia-related decreases in e voked potential produced by (R)-flurbiprofen were dose-dependent. Comp aring similar doses of (R)- and (S)-flurbiprofen, the decrease in CSSE RP-amplitudes produced by the (S)-enantiomer was somewhat more pronoun ced, indicating a higher analgesic potency. 4 The present data indicat e that both enantiomers of flurbiprofen produce analgesic effects. Sin ce (R)-flurbiprofen caused only little toxicity in rats as compared wi th the (S)-enantiomer or the racemic compound, a reduction of the quan titatively most important side effects in the gastrointestinal tract m ight be achieved by employing (R)-flurbiprofen in pain therapy.