[Determination of octreotide in human plasma by HPLC-MS with solid-phase extraction and study on the relative bioavailability of domestic and imported octreotide injections].

AIM: To establish an HPLC-MS method for determination of octreotide in plasma and study the relative bioavailability of domestic and imported octreotide injections. METHODS: Octreotide 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 CH3 OH-1% HAc (80 : 20), the flow rate was 0.2 mL x 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 microg 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. RESULTS: The regressive curve was linear (r = 0.9997) within the range of 0.5 - 40 microg x L(-1) for octreotide. The pharmacokinetics parameters of domestic and imported injection were reply to one compartment model. The mean C(max) were (19 +/- 10) microg x L(-1) and (19 +/- 11) microg x L(-1), T(max) were (0.50 +/- 0.15) h and (0.52 +/- 0.20) h, T1/2 were (1.5 +/- 0.8) h and (1.5 +/- 0.8) h, AUC(0-7 h) were (50 +/- 25) h x microg x L(-1) and (50 +/- 25) h x microg x L(-1), respectively. The relative bioavailability of domestic to imported injection was 101% +/- 10%. CONCLUSION: The method is accurat and sensible for assay of plasma octreotide concentration. The results of statistics showed the two preparations were bioequivalent.