Abstract: AimTo evaluate the hypersensitivity reaction of the blank paclitaxel microemulsion and study the O/W paclitaxel microemulsion′s pharmacokinetics in rats. MethodsAn alternative paclitaxel microemulsion was prepared with small particle size. The hypersensitivity reaction of the blank microemulsion was investigated in guinea pigs. In pharmacokinetic study, 5 rats were given iv Taxol or paclitaxel microemulsion. Blood samples were collected at 0, 0.25, 0.5, 1, 2, 4, 6, 8, 10, 12, 14 h and the concentration of paclitaxel in plasma was determined by HPLC method. The data obtained were processed using 3P87 program. ResultsThe mean size of the microemulsion is 17.2 nm. The preparation of blank microemulsion did not show any hypersensitivity, while the injection of commercial product showed significant hypersensitivity. The concentration-time curve of paclitaxel microemulsion and commercial injection (Taxol) fitted a two-compartment model. The k₁₀,k₁₂,k₂₁ and AUC of paclitaxel microemulsion were 0.571·h^-1, 1.441·h^-1, 3.081·h^-1 and 34.98 mg·h·L^-1. Those of commercial injection were 1.291·h^-1, 1.271·h^-1, 0.511·h^-1 and 21.85 mg·h·L^-1. ConclusionThe blank paclitaxel preparation of micoemulsion reduced the hypersensitivity in guinea pigs compared with the blank commercial injection. The paclitaxel microemulsion has relatively longer circulating time in rats.