Abstract: AimTo establish an HPLC-MS method for determination of octreotide in plasma and study the relative bioavailability of domestic and imported octreotide injections. MethodsOctreotide in plasma samples were extracted with a Waters solid-phase extraction mini column. HPLC-MS was carried out using a Waters Xetrra C₁₈ column and a mobile phase consisting of CH₃OH-1% HAc (80∶20), the flow rate was 0.2 mL·min^-1, and the internal standard was 6,7,4′-OH-isoflavone, the SIR ions for quantification were m/z 1 014.4 for octreotide and m/z 317.6 for internal standard. A single dose of 200 μg of domestic or imported preparations was intramuscularly given to 18 healthy volunteers in a randomized crossover study. Octreotide concentration in plasma was determined by LC-MS method. The pharmacokinetics and bioavailability were studied. ResultsThe regressive curve was linear (^R=0.999 7) within the range of 0.5-40 μg·L^-1for octreotide. The pharmacokinetics parameters of domestic and imported injection were reply to one compartment model. The mean C_max were (19±10) μg·L^-1 and (19±11) μg·L^-1, t_max were (0.50±0.15) h and (0.52±0.20) h, t_1/2were (1.5±0.8) h and (1.5±0.8) h, AUC_0-7h were (50±25) h·μg·L^-1 and (50±25) h·μg·L^-1, respectively. The relative bioavailability of domestic to imported injection was 101%±10%. ConclusionThe method is accurat and sensible for assay of plasma octreotide concentration. The results of statistics showed the two preparations were bioequivalent.