Introduction: the presence of residual microorganisms after chemical-surgical preparation of root canals suggests the use of effective intracanal medication, biologically compatible with periapical tissues. Objective: compare the cytotoxicity of intracanal medications in gingival human fibroblasts. Methods: an experimental study was conducted with four different groups: control (G1), Clindamycin Hydrochloride 2g associated to dexamethasone phosphate 0.32g (Clindex) vehicled in alcoholic solution (G2), Clindex vehicled in polyethylene glycol 400 (G3), and NDP: paramonochlorophenol associated to dexamethasone phosphate 0.32g vehicled in polyethylene glycol 400 and saline solution (G4). The cells were stimulated with the medications for 24, 48 and 72 hours. Cell viability was evaluated with the technique of MTT analysis. Readings were performed in an ELISA spectrophotometer. Results: the groups were analyzed in terms of mitochondrial activity. G2 had the best results in the three times studied, followed by G3 and G4. A statistical analysis was performed (ANOVA and complemented by Tukey's test). Significant differences of 1% were found when comparing G2 and G3 with G4. Conclusion: the Clindamycin dexamethasone combination, irrespective of the vehicle, showed greater cell viability than paramonochlorophenol associated to dexamethasone phosphate.