Lappaconitine, isolated from Aconitum sinomontanum Nakai, was characterized as analgesic principle. IC50 value: Target: In vitro: In vivo: Lappaconitine was characterized as analgesic principle by our laboratory. The results suggest that lappaconitine can produce analgesia, possibly through a decrease in cellular calcium availability and PAG may be involved in the Ca2+ antagonistic effect on lappaconitine analgesia [1]. Changes in lappaconitine levels in blood, brain and spinal cord following subcutaneous (s.c.) injection were correlated with the analgesic activity at intervals up to 90 minutes after injection. The equianalgesic doses of lappaconitine (ED50 by the s.c. route and additive ED50 by the i.c.v. plus i.t. route) gave closely similar concentrations of the drug in brain and spinal cord. These results indicate that a simultaneous action of lappaconitine on supraspinal and spinal sites is likely to be important for the analgesia produced by systemically administered lappaconitine [2].