title: Dried blood spot on-card derivatization: an alternative form of sample handling to overcome the instability of thiorphan in biological matrix.
abstract: Thiorphan, the active metabolite of racecadotril, can undergo oxidation in biological matrices such as blood and plasma. In bioanalysis, a general approach for the stabilization of such a molecule is to derivatize the thiol group to a more stable thioether, often requiring complex handling procedures at the clinical site. In this research, the concept of dried blood spot (DBS) on-card derivatization was evaluated to stabilize thiorphan. DBS cards were in-house pre-treated with 2-bromo-3'-methoxyacetophenone and left to dry prior to blood spotting. Thiorphan was shown to be effectively derivatized to thiorphan-methoxyacetophenone once applied on the in-house pre-treated cards. Thiorphan-methoxyacetophenone was extracted by soaking a 6 mm DBS punch in methanol containing the internal standard (thiorphan-methoxyacetophenone-D₅). Chromatographic separation was achieved on a Waters XBridge C₁₈ column with a gradient elution of 5 mM NH₄HCO₃ and methanol in 2.5 min and detection by ESI(+)/MS/MS. A linear (weighted 1/x²) relationship was obtained over a concentration range of 5.00-600.00 ng/mL. The assay met regulatory guidelines acceptance criteria for sensitivity, selectivity, precision and accuracy, matrix effect, recovery, dilution integrity and multiple stability evaluations. The DBS on-card derivatization has shown to be an easy and reliable alternative form of sample collection for the quantification of thiorphan.
authors.affiliation: Algorithme Pharma, Laval, Quebec, Canada.
authors.forename: Jean-Nicholas
authors.initials: JN
authors.lastname: Mess
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Taillon
authors.forename: Cynthia
authors.initials: C
authors.lastname: Côté
authors.forename: Fabio
authors.initials: F
authors.lastname: Garofolo
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods; D059788:Dried Blood Spot Testing / Q000379:methods*; D004355:Drug Stability; D006400:Hematocrit; D006801:Humans; D016018:Least-Squares Analysis; D016014:Linear Models; D053719:Tandem Mass Spectrometry / Q000379:methods; D015244:Thiorphan / Q000097:blood* / Q000737:chemistry*
chemical_list: D015244:Thiorphan