Pregabalin is an analog of gamma aminobutyric acid, and selectively interacts with the alpha-2-delta subunit of the voltage dependent calcium channels. The aims of this study were to investigate the analgesic effects of intrathecal pregabalin in rat formalin tests and to compare between the pre-treatment and post-treatment group.

All experimental animals were randomly divided into pre- and post-treatment groups. In pre-treatment groups, pregabalin (0.003 µg, 0.01 µg, 0.03 µg, 0.1 µg, n = 6 at each group) was administered through the intrathecal catheter 10 min prior to formalin injection. In post-treatment groups, pregabalin (0.01 µg, 0.03 µg, 0.1 µg, 0.3 µg, n = 6 at each group) was administered through the catheter 10 min after formalin injection. Formalin (50 ml, 5%) was injected in the left hind paw. We counted the number of flinching as a pain behavior for 60 min to quantify the nociceptive response.

The withdrawal responses which were represented by flinching count, were decreased dose dependently in the phase 2, in all groups (pre-treatment and post-treatment group), while there were less analgesic effects and ceiling effects in the phase 1. There was more significant decreasing flinching number in the pre-treatment group than that in the post-treatment group.

Intrathecal pregabalin has preemptive analgesic effect and may be useful in the management of inflammation induced hyperalgesia.