Pharmacokinetic study of orphenadrine using high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS)

We developed and validated a simple, rapid, and accurate HPLC–MS/MS method with simple protein precipitation for the determination of orphenadrine. Injection-to-injection running time was 3 min with a retention time of orphenadrine of 1.1 min. The linear assay range was 1–200 ng/mL (r2 > 0.99). The intra- and inter-assay imprecisions were CV 0.6–4.2% and CV 1.6–6.1%, respectively. The accuracy, extraction recovery, specificity and stability were satisfactory. Using the measured plasma concentrations of orphenadrine in 24 healthy subjects, pharmacokinetic profiles of orphenadrine were evaluated (AUC0–72, 1565 ± 731 ng h/mL, Cmax 82.8 ± 26.2 ng/mL, Tmax 3.0 ± 0.9 h, elimination half-life 25.8 ± 10.3 h).