Introduction:
The hyperplasia of synovial fibroblasts is considered to be essential for the evolution of joint destruction in rheumatoid arthritis (RA). Previously, we reported that anti-rheumatic drugs, both COX inhibitors and disease-modifying anti-rheumatic drugs inhibit proliferation of synoviocytes in vitro. The presented study investigates the effect of anti-epileptic drugs on the viability and proliferation of synovial fibroblasts in vitro.

Material and Methods:
Experiments were conducted on human synoviocytes derived from an RA patient and rabbit synoviocytes cell line HIG-82. Cell proliferation and viability were assessed by means of BrdU assay and MTT assay, respectively. The IC₅₀ value (the concentration of drug necessary to induce 50% inhibition) together with confidence limits was calculated.

Results:
Carbamazepine inhibited proliferation of human fibroblasts and viability of HIG-82 with IC₅₀ values of 86 µM and 82 µM, respectively. Diphenylhydantoin, valproate and phenobarbital inhibited viability of HIG-82 cells with the IC₅₀ values of 110, 500 and 1031 µM, respectively.

Conclusions:
Based on these findings, it can be suggested that anti-epileptic drugs may have a disease-modifying effect on rheumatoid synovial proliferation.