Development and validation of a sensitive and selective LC–MS/MS method for determination of tacrolimus in oral fluids

Tacrolimus Concentration in Saliva of Kidney Transplant Recipients: Factors Influencing the Relationship with Whole Blood Concentrations

OBJECTIVE

The objective of this study was to examine the association between tacrolimus concentration in oral fluids and in whole blood and to investigate the various factors that influence this relationship.

PATIENTS AND METHODS

Forty-six adult kidney transplant recipients were included in the study. Study A (ten patients) included the collection of several paired oral fluid samples by passive drool over a 12-h post-dose period. Study B (36 patients) included the collection of oral fluids pre-dose and at 2 h after the tacrolimus dose under three conditions: un-stimulated, after stimulation with a tart candy, and after mouth rinsing. The tacrolimus concentration in oral fluids was measured by a specially developed sensitive and specific liquid chromatography mass spectrometry method. A salivary transferrin concentration of >1 mg/dL was used as a cut-off value for oral fluid blood contamination.

RESULTS

Rinsing the oral cavity before sampling proved to provide the most suitable sampling strategy giving a correlation coefficient value of 0.71 (p = 0.001) between the tacrolimus concentration in oral fluids and the tacrolimus concentration in whole blood at trough. Mean and 95% confidence interval of tacrolimus concentration in oral fluids at the pre-dose concentration for samples collected after mouth rinsing was 584 (436, 782) pg/mL. The ratio of the tacrolimus concentration in oral fluids to the tacrolimus concentration in whole blood (*100) was 11% (95% confidence interval 9-13) for all sampling times. Oral fluid pH or weight of a saliva sample did not influence the tacrolimus concentration in oral fluids. Tacrolimus distribution into oral fluids exhibited a delay with a pronounced counter-clockwise hysteresis with respect to the time after dose. A multivariate analysis of variance revealed that the tacrolimus concentration in oral fluids is related to the tacrolimus concentration in whole blood and tacrolimus plasma-binding proteins including albumin and cholesterol.

CONCLUSION

An optimal sampling strategy for the determination of the tacrolimus concentration in oral fluids was established. Measuring the tacrolimus concentration in oral fluids appears to be a feasible and non-invasive method for predicting the concentration of tacrolimus in whole blood.

A multidrug LC–MS/MS method for the determination of five immunosuppressants in oral fluid

Aim: This study aimed: to develop and validate an LC–MS/MS method for mycophenolic acid, tacrolimus, sirolimus, everolimus and cyclosporin A in oral fluid (OF), as an essential tool to study the usefulness of OF as an alternative matrix for immunossuppressants’ therapeutic drug monitoring; and to find the best OF collector for these analytes. Materials & Methods: Chromatographic separation was achieved using an XBridge® Shield RP18 analytical column maintained at 65ºC, using 2 mM ammonium formate and 0.1% formic acid in water (A) and acetonitrile (B) as mobile phase. OF sample was extracted with solid phase extraction after sonication and protein precipitation. Results & Conclusions: Method validation met all the acceptance criteria. LODs were 0.05–1 ng/ml, and LOQs 0.1–5 ng/ml. Silanized tubes offered the best recoveries. The method was successfully applied to 31 OF specimens, describing everolimus detection in OF for the first time. Conclusion: The proposed method is sensitive enough for the detection of OF trough concentrations in patients receiving immunosuppressants when using an appropriate OF collector.

Urine and oral fluid drug testing in support of pain management

In recent years, the abuse of opioid drugs has resulted in greater prevalence of addiction, overdose, and deaths attributable to opioid abuse. The epidemic of opioid abuse has prompted professional and government agencies to issue practice guidelines for prescribing opioids to manage chronic pain. An important tool available to providers is the drug test for use in the initial assessment of patients for possible opioid therapy, subsequent monitoring of compliance, and documentation of suspected aberrant drug behaviors. This review discusses the issues that most affect the clinical utility of drug testing in chronic pain management with opioid therapy. It focuses on the two most commonly used specimen matrices in drug testing: urine and oral fluid. The advantages and disadvantages of urine and oral fluid in the entire testing process, from specimen collection and analytical methodologies to result interpretation are reviewed. The analytical sensitivity and specificity limitations of immunoassays used for testing are examined in detail to draw attention to how these shortcomings can affect result interpretation and influence clinical decision-making in pain management. The need for specific identification and quantitative measurement of the drugs and metabolites present to investigate suspected aberrant drug behavior or unexpected positive results is analyzed. Also presented are recent developments in optimization of test menus and testing strategies, such as the modification of the standard screen and reflexed-confirmation testing model by eliminating some of the initial immunoassay-based tests and proceeding directly to definitive testing by mass spectrometry assays.

Saliva: a reliable sample matrix in bioanalytics

Saliva is gaining increasing attention as a bioanalytical sample matrix. Mostly because of the easy and noninvasive collection, it is not only beneficial in endocrinological and behavioral science, but also in pediatrics. Saliva also has the advantage of being the only body fluid which can be collected even during physical exercise, for example, during sportive activities, and there are physiological characteristics that make it superior to serum/plasma or urine for specific scientific questions. This review provides an insight into the physiology of saliva formation, explaining how certain compounds enter this bodily fluid, and gives advice for collection, storage and analytical methods. Finally, it presents a number of reliable and proven applications for saliva analysis from scientific fields including endocrinology, sports medicine, forensics and immunology.