Development and validation of a highly sensitive gradient chiral separation of pramipexole in human plasma by LC-MS/MS.

Aim: Development of a high-sensitivity chiral LC-MS/MS method was required to evaluate a combination of pramipexole (S-PPX) and its enantiomer dexpramipexole (R-PPX) in a proposed clinical trial. The previously available methods suffered from low sensitivity for the (S)-enantiomer in the presence of the more abundant (R)-enantiomer. Based on the projected dosing regimen in the clinical trial, a 5000-fold improvement in sensitivity was required for the (S)-enantiomer.

Methodology: Spiked human plasma samples were extracted by liquid-liquid extraction using ethyl acetate and injected onto a CHIRALPAK ID column under pH gradient conditions.

Conclusion: An improved analytical method was developed and validated with a final LLQ for (S)-PPX of 0.1 ng/ml in the presence of 2000 ng/ml of (R)-PPX.