OBJECTIVE To analyze pharmacokinetic parameters of sulfadiazine in rabbits.METHODS A single dose of 300 mg·kg^-1 sulfadiazine was given intravenously to 20 healthy rabbits.The concentrations of sulfadiazine in different time and were determined by ultraviolet spectrophotometer and pharmacokinetic parameters were calculated. RESULTS The time-concentration curve of sulfadiazine in rabbit coincided with the two-compartment open model. Slow and fast rate-metabolism for sulfadiazine were distinguished in this study. The pharmacokinetic parameters of slow rate-metabolism were as follows:V_C (0.24±0.09) L·kg^-1,V(0.62±0.22)L·kg^-1,AUC(0.11±0.05)g·h·mL^-1,CL(3.8±1.5) mL·min^-1,t_1/2α(3.3±1.3)min,t_1/2β(122±21)min. The pharmacokinetic parameters of fast rate-metabolism were as follows: V_C(0.19±0.10)L·kg^-1,V(0.45±0.17)L·kg^-1,AUC(0.062±0.022)g·h·mL^-1,CL(6.0±2.4)mL·min^-1,t_1/2α(2.1±0.9) min,t_1/2β(53±5) min. When being compared with that of slow rate-metabolism,AUC,t_1/2β of fast rate-metabolism were significantly decreased,CL of fast rate-metabolism was significantly increased. CONCLUSION Slow and fast rate-metabolism for sulfadiazine in rabbit can be distinguished. This study provides a scientific basis for clinical use of sulfadiazine.