Measurement of neosaxitoxin in human plasma using liquid-chromatography tandem mass spectrometry: Proof of concept for a pharmacokinetic application.

Neosaxitoxin, a member of the saxitoxin family of paralytic shellfish poisoning toxins, has shown potential as an effective, long-acting, anesthetic. We describe the development and validation of a highly sensitive method for measurement of neosaxitoxin in human plasma using liquid chromatography tandem mass spectrometry (LC-MS/MS) and provide evidence for its use in a human pharmacokinetic study. Samples were prepared using cation exchange solid phase extraction followed by hydrophilic interaction liquid chromatography and MS/MS detection in positive electrospray ionization mode.