Analysis of Clozapine and Norclozapine in Plasma using Automated On-line Sample Preparation and LC–MS/MS
The analysis of clozapine and norclozapine in plasma using automated on-line sample preparation and LC–MS/MS
Clozapine is a dibenzodiazepine drug used in the treatment of schizophrenia. It is uniquely effective in patients resistant to therapy with other antipsychotics. In addition to mandatory haematological monitoring to minimize the risk of agranulocytosis, there is a large variation (50-fold) in clozapine dose requirement that complicates dose assessment. Clozapine is metabolized via N-demethylation, N-oxidation, and aromatic hydroxylation, amongst other pathways. N-Desmethylclozapine [norclozapine], accumulates in plasma to concentrations similar to those of clozapine. Clozapine N‑oxide accumulates in plasma to approximately 10% of the plasma clozapine concentration but is not measured routinely. Changes in smoking habit can have a large effect on clozapine dose requirement. On average the clozapine dose for non-smokers is half that required for smokers due to induction of the cytochrome P450 enzyme in CYP1A2 smokers. Accurate measurement of plasma clozapine and norclozapine concentrations may help understand issues related to dose optimization and adherence. Current methodology in our research laboratory for plasma clozapine and norclozapine measurement involves off-line liquid-liquid extraction (LLE) into methyl tert-butyl ether at pH 10.6 with manual transfer of the extract to an HPLC-UV system. Clozapine N-oxide is not extracted.
LCGC’s Year in Review: Highlights in Liquid Chromatography
December 20th 2024This collection of technical articles, interviews, and news pieces delves into the latest innovations in LC methods, including advance in high performance liquid chromatography (HPLC), ultrahigh-pressure liquid chromatography (UHPLC), liquid chromatography–mass spectrometry (LC–MS), and multidimensional LC.
Next Generation Peak Fitting for Separations
December 11th 2024Separation scientists frequently encounter critical pairs that are difficult to separate in a complex mixture. To save time and expensive solvents, an effective alternative to conventional screening protocols or mathematical peak width reduction is called iterative curve fitting.
