Influence of the Vehicle and Antibiotic Formulation on Cytotoxicity of Triple Antibiotic Paste

Introduction The aim of this study was to assess the influence of antibiotic formulations (tablet/capsule [TC] or United States Pharmacopeia [USP]-grade antibiotics) and vehicles (water [H2O] or macrogol + propylene glycol [MP]) on the cytotoxicity and pH of triple antibiotic pastes (TAPs). Methods L929 fibroblasts were exposed to TAPs prepared with TC or USP-grade antibiotics mixed with H2O or MP for 72 hours. Each isolated antibiotic with each vehicle, each isolated vehicle, and the culture medium were used as controls. Cytotoxicity was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and neutral red assays. The pH was measured after 3 and 8 hours of immersion of the pastes in water. Data were analyzed using analysis of variance, the Bonferroni or Tukey posttests (α = 0.05), and the Pearson correlation test (α = 0.05). Results The pastes prepared with TC were less cytotoxic than pastes prepared with USP-grade antibiotics (P < .05), and pastes with the MP vehicle were less cytotoxic than pastes with H2O (P < .05). TC TAP + MP showed the lowest cytotoxicity, whereas USP-grade TAP + H2O showed the highest cytotoxicity (P < .05). All TAPs showed a pH ranging from 4.64–5.20. Irrespective of the vehicle, USP-grade TAP showed a lower pH than TC TAP (P < .05). TAPs with H2O had a lower pH than TAPs with MP (P < .05). Conclusions The vehicle and the antibiotic formulations influenced the cytotoxicity and pH of TAP. The pastes prepared with TC and MP were less acidic and less cytotoxic than the type prepared with USP-grade antibiotics and H2O.