Quantification of tricyclic antidepressants using UPLC-MS/MS.

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.

Unresolved discrepancies between cannabinoid test results for infant urine.

BACKGROUND: False-positive drug screen results for tetrahydrocannabinol (THC) have been observed. This study investigated the rate of unconfirmed positive screen results in infant and noninfant urine samples and evaluated possible reasons for differences. METHODS: The rate of unconfirmed positive THC screen results for urine samples was determined retrospectively in 2 independent data sets (n = 14,859, reference laboratory; n = 21,807, hospital laboratory) by comparing positive immunoassay-based drug screen results with the associated results of confirmation tests. We then assessed the rate of positive THC screens for samples with varying likelihoods of cannabinoid presence to evaluate the contribution of infant-specific urine constituents to positive results. Finally, a method to detect a THC metabolite (11-hydroxy-Δ9-THC) that occurs in meconium was developed to determine its prevalence in infant urine. RESULTS: Positive screen results failed to confirm more frequently in samples from infants (47%) than in noninfants (0.8%). The hospital laboratory observed a similar discrepancy with a different immunoassay. Infant samples with a high likelihood of containing cannabinoids despite negative confirmatory results had a similar rate of positive screening results (50%, n = 20), whereas all samples with a low likelihood of containing cannabinoids screened negative (n = 23). 11-Hydroxy-Δ9-THC was not detected in any infant urine sample tested (n = 16). CONCLUSIONS: Conventional confirmatory methods for THC may be inappropriate for urine samples from infants. Our results suggest that one or more currently unrecognized THC-associated compounds are responsible for positive THC screen results for infant urine, as opposed to an infant-associated interference.

Patterns of free (unconjugated) buprenorphine, norbuprenorphine, and their glucuronides in urine using liquid chromatography-tandem mass spectrometry.

Patterns of buprenorphine and metabolites were examined in 1946 positive urine samples analyzed by liquid chromatography-tandem mass spectrometry for free (unconjugated) buprenorphine and norbuprenorphine (quantitative, 2 to 1000 ng/mL) and buprenorphine-glucuronide (B3G) and norbuprenorphine-glucuronide (N3G) (semi-quantitative, 5 to 1000 ng/mL). Two distribution patterns predominated with 49.1% positive for norbuprenorphine, B3G, and N3G and 41.6% positive for buprenorphine, norbuprenorphine, B3G, and N3G. Buprenorphine, positive in 45.5% of samples, was mostly < 5 ng/mL (median 6.1 ng/mL), but 9.8% were > 1000 ng/mL. Norbuprenorphine, B3G, and N3G had semi-Gaussian distributions with medians of 64.7, 108, and 432 ng/mL, respectively. With buprenorphine < 100 ng/mL (767 samples) or ≥ 100 ng/mL (19 quantifiable samples), the respective median metabolic ratios (free norbuprenorphine/free buprenorphine) were 25.0 and 0.15. In 12 retested "> 1000 ng/mL" buprenorphine samples, free buprenorphine was 4160 to 39,400 ng/mL and free naloxone 2140 to 9560 ng/mL. In 87 subsequent samples with buprenorphine < 20 ng/mL, naloxone concentrations were < 50 ng/mL. Concentrations of buprenorphine > 100 ng/mL (particularly with low metabolite concentrations) are suspect of urine adulteration with medication (4% in the database) that can be checked in most cases by concurrent analysis for naloxone.