LC-MS in Drug Analysis

Kamisha L. Johnson-Davis, JoEtta M. Juenke, Rebecka Davis, Gwendolyn A. McMillin, Johnson-Davis, Kamisha L., Juenke, JoEtta M., Davis, Rebecka, McMillin, Gwendolyn A.

Depression is a psychiatric condition that affects about 120 million people worldwide and can interfere with independence and productivity in essentially all aspects of daily life. Depression is also associated with risk of self-harm, and ultimately suicide. Antidepressant medications are widely used to treat symptoms of depression. While there are several classes of antidepressants, therapeutic drug management (TDM) is most common for the tricyclic antidepressants (TCAs). TDM of TCAs is important due to wide inter-individual variability in pharmacokinetics, production of active metabolites, and a high risk of drug-drug interactions. In addition, TDM of some TCAs can be used to optimize dose, wherein concentration relationships are recognized for both therapeutic response and potentially life-threatening toxicity. In many clinical scenarios, TDM of TCAs is accomplished by currently available point of care or automated immunoassays that provide a "total" TCA concentration. However, these assays may not be adequately specific to meet the needs of all clinical scenarios, and hence, chromatographic separation and quantification of individual TCA parent drugs and active metabolites that may contribute to the "total" TCA concentration is sometimes required. This chapter describes an analytical method designed to detect and/or quantify clinically significant concentrations of nine TCAs (amitriptyline, nortriptyline, imipramine, desipramine, doxepin, nordoxepin, protriptyline, clomipramine, and norclomipramine) in serum or plasma, using ultra pressure liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample preparation employs a rapid protein precipitation with 50:50 MeOH:acetonitrile, high speed centrifugation, and injection of 5 μL of supernatant onto the instrument, with a 5 min run-time.