Determination of pseudoephedrine in dog plasma by LC-MS and study of its pharmacokinetics

Aim: To establish an LC-MS method for determination of pseudoephedrine in Beagle dog's plasma and to study its pharmacokinetics. Method: After alkalizing with a mixture of 1% NaOH 50 μl and 4% Na₂CO₃ 2.5 ml, the plasma samples, with the addition of phenylpropanolamine, were extracted with 4 ml ether. HPLC analysis was carried out through ODS C₁₈ Shim-pack column (5 μm, 250 mm × 2.0 mm). The mobile phase consisted of acetonitrile-0.2% acetic acid and 0.005 mmol/L ammionium acetate (20:80, v/v) at a flow rate of 0.2 ml/min. The column temperature is 40 °C. Analysis in the mass spectrometer was performed in the selected-ion monitoring model. Pseudoephedrine concentrations in plasma were determined and pharmacokinetic parameters were also estimated. Result: The standard curve was linear in the range of 0.016 ∼ 2.00 μg/ml. Recoveries of pseudoephedrine at 0.062, 0.25 and 2.0 μg/ml were 93.18%, 99.40% and 96.90% respectively. The relative standard derivation of intra-day and inter-day was smaller than 10%. After ig a single dose, the pharmacokinetic parameters of pseudoephedrine were: c_max 0.71 ± 0.16 μg/ml, t_max: 2.3 ± 0.8 h, t_1/2: 7.15 ± 1.08 h, MRT: 11.36 ± 1.54 h, AUC_0-τ: 5.86 ± 0.93 μg · h/ml. Conclusion: The bioanalytical method of LC-MS is suitable for pharmacokinetics study of pseudoephedrine.