The detection of 19-norsteroids abuse in doping controls currently relies on the determination of 19-norandrosterone (19-NA) by gas chromatography-tandem mass spectrometry (GC-MS/MS). An additional confirmatory analysis by gas chromatography coupled to isotope ratio mass spectrometry (GC-C-IRMS) is performed on samples showing 19-NA concentrations between 2.5 and 15 ng/ml and not originated from pregnant female athletes or female treated with 19-norethisterone.19-Noretiocholanolone (19-NE) is typically produced to a lesser extent as a secondary metabolite. The aim of this work was to improve the GC-C-IRMS confirmation procedure for the detection of 19-norsteroids misuse. Both 19-NA and 19-NE were analyzed as target compounds (TCs), whereas androsterone (A), pregnanediol (PD), and pregnanetriol (PT) were selected as endogenous reference compounds (ERCs). The method was validated and applied to urine samples collected by three male volunteers after the administration of nandrolone-based formulations.Before the instrumental analysis, urine samples (<25 ml) were hydrolyzed with β-glucuronidase from Escherichia coli and extracted with n-pentane. Compounds of interest were purified through a single (for PT) or double (for 19-NE, 19-NA, A, and PD) liquid chromatographic step, to reduce the background noise and eliminate interferences that could have affect the accuracy of δ 13 C values. The limit of quantification (LOQ) of 2 ng/ml was ensured for both 19-NA and 19-NE. The 19-NE determination could be helpful in case of "unstable" urine samples, in late excretion phases or when coadministration with 5α-reductase inhibitors occur.

Prednisone and prednisolone are two anti‐inflammatory steroidal drugs listed by the World Anti‐Doping Agency (WADA) within the class of glucocorticoids, which are prohibited “in competition” and when administered systemically. Their presence in collected urine samples may be attributed, if no exogenous administration has occurred, to an in situ microbial formation from endogenous steroids. In this work, a gas chromatography coupled to carbon isotope ratio mass spectrometry (GC‐C‐IRMS) method was developed and validated to distinguish an exogenous origin from an endogenous one. Eight prednisone/prednisolone pharmaceutical preparations commercially available in Italy were analysed to establish an exogenous δ13C value reference range (−28.96 ± 0.39‰). No more than 25 mL of urine was processed and no derivatization nor intentional steroids structure modifications were performed before the GC‐C‐IRMS analysis. A first HPLC purification step was set up to isolate the three endogenous reference compounds (ERCs) selected (tetrahydro‐11‐deoxycortisol (THS), pregnanediol (PD), and pregnanetriol (PT)), while a second LC purification was necessary to separate prednisone from prednisolone. In the GC‐C‐IRMS analysis, two different GC run methods were set up to guarantee better sensitivity and selectivity for each compound. Both prednisone and prednisolone showed signals (m/z 44) with amplitudes within the method linearity range to a lower urinary concentration of 20 ng/mL (< WADA reporting level, 30 ng/mL). The method was fully validated according to WADA requirements. As a proof of concept, urine samples collected from two excretion studies in healthy male volunteers, after a prednisone or prednisolone administration, were analysed by the proposed method, demonstrating its applicability for the analysis of real samples.

5α‐reductase inhibitors (5‐ARIs) are considered by the World Anti‐doping Agency as potential confounding factors in evaluating the athlete steroid profile, since they may interfere with the urinary excretion of several diagnostic compounds. We herein investigated 5α‐reductase inhibitors from a different perspective, by verifying their influence on the carbon isotopic composition of 5α‐ and 5β‐reduced testosterone and nandrolone metabolites. The GC‐C‐IRMS analysis was performed on a set of urine samples collected from three male Caucasian volunteers after the acute and chronic administration of finasteride in combination with the intake of 19‐norandrostenedione, a nandrolone precursor. The excretion and the isotopic profile of androsterone (A), etiocholanolone (Etio) 5α‐androstane‐3α,17β‐diol (5αAdiol), and 5β‐androstane‐3α,17β‐diol (5βAdiol) were determined as well as those of 19‐norandrosterone (19‐NA) and 19‐noretiocholanolone (19‐NE). Pregnanediol (PD) and pregnanetriol (PT) were also measured as endogenous reference compounds to define the individual endogenous isotopic profile. Our results confirmed the impact of finasteride, especially if chronically administered, on the enzymatic pathway of testosterone and nandrolone, and pointed out the influence of 5‐ARIs on δ13C values of the selected target compounds determined in the IRMS confirmation analysis.

Twenty‐two pharmaceutical formulations containing prednisolone or prednisone commercially available in Italy, Belgium, Spain, Brazil, and India were analyzed through a specific gas chromatography combustion isotope ratio mass spectrometry (GC‐C‐IRMS) method. All of them showed typical non‐endogenous δ13C values, except for the Belgian nasal spray, Sofrasolone®, with a less depleted 13C content (−17.84 ± 0.18‰). Observational studies were performed on two volunteers in therapy with Sofrasolone® to confirm the applicability of the method and to suggest adequate interpretation criteria also in the case of drugs with less negative δ13C values. Urine samples were collected before, during, and within the 36 hours after the administration of the spray. Both δ13C values and urinary concentrations of prednisolone and prednisone were evaluated. All samples were subjected to an adequate pre‐treatment (enzymatic hydrolysis, liquid/liquid extraction, and two sequential HPLC steps) before injection to the GC‐C‐IRMS instrument, according to the method recently developed and validated in our laboratory. Pregnanediol (PD), tetrahydro‐11‐deoxycortisol (THS), and pregnanetriol (PT) were selected as endogenous reference compounds (ERC). The excretion profile was estimated through liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) method used routinely for the quali‐quantitative detection of glucocorticoids. δ13C values and urinary levels of prednisolone and prednisone were also determined after the intake of one single vial of Sintredius®, a prednisolone oral formulation with a conventional more negative δ13C value (−29.28 ± 0.25‰). Finally, the potential masking effect that combined therapy with Sofrasolone® and Sintredius® could induce on the IRMS findings was investigated.