Antinociceptive effects of (±)-, (+)- and (-)-nefopam in mice

Abstract

The antinociceptive activity of (±)‐, (+)‐ and (‐)‐nefopam in mice has been examined using the hot‐plate, formalin and tail‐flick tests. Nefopam was administered by the intraperitoneal, intracerebroventricular (i.c.v.) and intrathecal (i.th.) routes. Intraperitoneal injection of (±)‐nefopam (10–20 mg kg⁻¹) had powerful analgesic effects in the hot‐plate and formalin tests. In the tail‐flick test it produced a weak, but significant elevation of the response latencies. In spinalized animals, however, the effect was abolished, indicating that nefopam prolonged the tail‐flick latencies by activation of descending pain‐modulating pathways. (±)‐Nefopam (5–20 μg) elicited analgesia in the hot‐plate test after i.c.v. or i.th. injection. These findings suggest that nefopam has both a spinal and a supraspinal site of action. (+)‐Nefopam was significantly more potent than (‐)‐nefopam after both systemic and central administration.