Rapid Determination of Metoclopramide Level in Human Plasma by LC-MS/MS Assay

A rapid liquid chromatographic tandem mass spectrometry (LC-MS/MS) assay for the measurement of metoclopramide level in human plasma was developed and validated. One ml plasma samples containing metoclopramide and 0.25 µg of loratadine as internal standard (IS) were extracted with 5 ml tert-butyl methyl ether and reconstituted in 80 µl of acetonitrile. Analysis was performed on reversed phase Atlantis dC18 column using a mobile phase of 0.4% formic acid (pH=3.0 ± 0.05) and acetonitrile (20:80, v:v) delivered at a flow rate of 0.25 ml/minute. Analytes were quantified multiple reaction monitoring in positive ion mode with transition mass to charge ratio (m/z) of 299.8→226.9 and 383.4→337.2 for metoclopramide and IS, respectively. Retention times of metoclopramide and IS were around 1.4 and 2.1 minutes, respectively. No significant matrix effect was observed on metoclopramide and IS peaks. Detection limit of metoclopramide in plasma was 0.3 ng/ml. Relationship between metoclopramide level and peak area ratio of metoclopramide / IS was linear (R2 ³ 0.9964) in the range of 0.5–100 ng/ml and inter-day coefficient of variations (CV) and absolute bias were ≤ 12.0% and ≤ 6.0%, respectively. Mean extraction recoveries for metoclopramide and the IS were 91% and 88%, respectively. The method was applied to assess stability of metoclopramide under various conditions generally encountered in the clinical laboratory. Stability of metoclopramide was ≥ 94% and ≥ 95% after 24 hours at room temperature or 48 hours at -20 ºC, respectively, in processed samples and 100% and ≥ 99% after 24 hours at room temperature or 12 weeks at -20 ºC, respectively, in unprocessed samples.