Technical and health governance aspects of the external quality assessment system for classical and new psychoactive substances analysis testing in blood.

New psychoactive substances (NPS) are uncontrolled analogues of existing drugs or newly synthesized chemicals that exhibit psychopharmacological effects. Due to their diverse nature, composition, and increasing prevalence, they present significant challenges to the healthcare system and drug control policies. In response, healthcare system laboratories have developed analytical methods to detect NPS in biological samples. As a Regional Reference Centre, the Sicilian CRQ Laboratory (Regional Laboratory for Quality Control) developed and conducted an External Quality Assessment (EQA) study to assess, in collaboration with the Istituto Superiore di Sanità (ISS), the ability of different Italian laboratories to identify NPS and traditional drugs of abuse (DOA) in biological matrices. Two blood samples were spiked with substances from various drug classes, including synthetic cannabinoids, cathinones, synthetic opiates, and benzodiazepines, at concentrations ranging from 2 to 10 ng/mL. The blood samples were freeze-dried to ensure the stability of DOA and NPS. Twenty-two laboratories from the Italian healthcare system participated in this assessment. The information provided by the laboratories during the registration in an in-house platform included a general description of the laboratory, analytical technique, and the chosen panels of analytes. The same platform was employed to collect and statistically analyze the data and record laboratory feedback and comments. The evaluation of the results revealed that the participating laboratories employed three different techniques for analyzing the samples: GC-MS, LC-MS, and immunoenzymatic methods. Approximately 90 % of the laboratories utilized LC-MS techniques. Around 40 % of false negative results were obtained, with the worst results in the identification of 5-chloro AB PINACA. The results showed that laboratories that used LC-MS methods obtained better specificity and sensitivity compared to the laboratories using other techniques. The results obtained from this first assessment underscore the importance of external quality control schemes in identifying the most effective analytical techniques for detecting trace molecules in biological matrices. Since the judicial authorities have not yet established cut-off values for NPS, this EQA will enable participating laboratories to share their analytical methods and expertise, aiming to establish common criteria for NPS identification.

Principles of conducting alcohol concentration measurements and providing opinions in sobriety cases. / Zasady przeprowadzania pomiarów stezenia alkoholu oraz opiniowania w sprawach trzezwosci.

Recommendations formulated by the Professor Jan Sehn Institute of Forensic Research in Kraków and approved by the Board of the Polish Society of Forensic Medicine and Criminology on November 28, 2023.

Prevention of Substance Use Disorders.

Methods to prevent substance use disorders (SUDs) act on the individual risk factors for addiction. Most adults with SUD initiated substance use during their teenage years, so preventive interventions during adolescence are critical. Antisubstance use messaging, routine screening, and pathways for referral to treatment can be extended into all settings whereby trusted adults interact with adolescents such as sports, mentoring programs, child protective services, and juvenile justice settings. Pediatric primary care is an ideal place to incorporate preventive counseling and screening for substance use. Evidence-based technologic interventions for primary, secondary, and tertiary prevention are needed.

Frequency and type of adverse analytical findings in athletics: Differences among disciplines.

Athletics is a highly diverse sport that contains a set of disciplines grouped into jumps, throws, races of varying distances, and combined events. From a physiological standpoint, the physical capabilities linked to success are quite different among disciplines, with varying involvements of muscle strength, muscle power, and endurance. Thus, the use of banned substances in athletics might be dictated by physical dimensions of each discipline. Thus, the aim of this investigation was to analyse the number and distribution of adverse analytical findings per drug class in athletic disciplines. The data included in this investigation were gathered from the Anti-Doping Testing Figure Report made available by the World Anti-Doping Agency (from 2016 to 2018). Interestingly, there were no differences in the frequency of adverse findings (overall,~0.95%, range from 0.77 to 1.70%) among disciplines despite long distance runners having the highest number of samples analysed per year (~9812 samples/year). Sprinters and throwers presented abnormally high proportions of adverse analytical findings within the group of anabolic agents (p < 0.01); middle- and long-distance runners presented atypically high proportions of findings related to peptide hormones and growth factors (p < 0.01); racewalkers presented atypically high proportions of banned diuretics and masking agents (p = 0.05). These results suggest that the proportion of athletes that are using banned substances is similar among the different disciplines of athletics. However, there are substantial differences in the class of drugs more commonly used in each discipline. This information can be used to effectively enhance anti-doping testing protocols in athletics.

Review of the Current State of Urine Drug Testing in Chronic Pain: Still Effective as a Clinical Tool and Curbing Abuse, or an Arcane Test?

PURPOSE OF REVIEW: Therapeutic use, misuse, abuse, and diversion of controlled substances in managing chronic non-cancer pain remain a major concern for physicians, the government, payers, and patients. The challenge remains finding effective diagnostic tools that can be clinically validated to eliminate or substantially reduce the abuse of controlled prescription drugs, while still assuring the proper treatment of those patients in pain. Urine drug testing still remains an important means of adherence monitoring, but questions arise as to its relevance and effectiveness. This review examines the role of UDT, determines its utility in current clinical practice, and investigates its relevance in current chronic pain management. RECENT FINDINGS: A review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Literature was searched from year 2000 to present examining the relevance and role of UDT in monitoring chronic opioid therapy along with reliability and accuracy, appropriate use, overuse, misuse, and abuse. There are only a limited number of reviews and investigations on UDT, despite the fact that clinicians who prescribe controlled medications for chronic states commonly are expected to utilize UDT. Therefore, despite highly prevalent use, there is a limited publication base from which to draw in this present study. Regardless of experience or training background, physicians and healthcare providers can much more adequately assess opioid therapy with the aid of UDT, which often requires confirmatory testing by a laboratory for clinical and therapeutic prescribing decisions. It has become a strongly recommended aspect of pain care with controlled substances locally, regionally, and nationally. Incorporating UDT for all patients in whom chronic opioid therapy is undertaken is consistent with state and national guidelines and best practice strategies. Practice standards vary as to the frequency of UDT locally, regionally, and nationally, however.

Finding the proverbial needle: Non-targeted screening of synthetic opioids in equine plasma.

Synthetic opioids are a class of compounds that are of particular concern due to their high potency and potential health impacts. With the relentless emergence of new synthetic opioid derivatives, non-targeted screening strategies are required that do not rely on the use of library spectra or reference materials. In this study, product ion searching, and Kendrick mass defect analysis were investigated for non-targeted screening of synthetic opioids. The estimated screening cut-offs for these techniques ranged between 0.05 and 0.1 ng/mL. These techniques were designed to not be reliant on a particular vendor's software, meaning that they can be applied to existing drug screening protocols, without requiring the development and validation of new analytical procedures. The efficacy of the developed techniques was tested through blind trials, with spiked samples inserted amongst authentic plasma samples, which demonstrated the usefulness of these methods for high-throughput screening. The use of a non-targeted screening workflow that contains complementary techniques can increase the likelihood of detecting compounds of interest within a sample, as well as the confidence in detections that are made.

Structure Elucidation of Urinary Metabolites of Fentanyl and Five Fentanyl Analogs using LC-QTOF-MS, Hepatocyte Incubations and Synthesized Reference Standards.

Fentanyl analogs constitute a particularly dangerous group of new psychoactive compounds responsible for many deaths around the world. Little is known about their metabolism, and studies utilizing liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) analysis of hepatocyte incubations and/or authentic urine samples do not allow for determination of the exact metabolite structures, especially when it comes to hydroxylated metabolites. In this study, seven motifs (2-, 3-, 4- and ß-OH as well as 3,4-diOH, 4-OH-3-OMe and 3-OH-4-OMe) of fentanyl and five fentanyl analogs, acetylfentanyl, acrylfentanyl, cyclopropylfentanyl, isobutyrylfentanyl and 4F-isobutyrylfentanyl were synthesized. The reference standards were analyzed by LC-QTOF-MS, which enabled identification of the major metabolites formed in hepatocyte incubations of the studied fentanyls. By comparison with our previous data sets, major urinary metabolites could tentatively be identified. For all analogs, ß-OH, 4-OH and 4-OH-3-OMe were identified after hepatocyte incubation. ß-OH was the major hydroxylated metabolite for all studied fentanyls, except for acetylfentanyl where 4-OH was more abundant. However, the ratio 4-OH/ß-OH was higher in urine samples than in hepatocyte incubations for all studied fentanyls. Also, 3-OH-4-OMe was not detected in any hepatocyte samples, indicating a clear preference for the 4-OH-3-OMe, which was also found to be more abundant in urine compared to hepatocytes. The patterns appear to be consistent across all studied fentanyls and could serve as a starting point in the development of methods and synthesis of reference standards of novel fentanyl analogs where nothing is known about the metabolism.

Analysis of cobalt for human sports drug testing purposes using ICP- and LC-ICP-MS.

Due to the current demands in the fight against manipulation of blood and blood components, commonly referred to as "blood doping" in sports drug testing, specific and sensitive detection methods enabling the detection of prohibited substances and methods of doping are required. Similar to illicit blood transfusions, erythropoiesis stimulating agents have been shown to be misused in sport, aiming at improving an athlete's aerobic capacity and endurance performance. Amongst other strategies, the administration of ionic cobalt (Co2+ ) can increase the number of erythrocytes by stimulating the endogenous erythropoietin (EPO) biosynthesis. Conversely, several organic Co-containing compounds such as cyanocobalamin (vitamin B12) are not prohibited in sports, and thus, an analytical differentiation of permitted and banned contributions to urinary Co-concentrations is desirable. An excretion study with daily applications of either 1 mg of CoCl2 or 1 mg of cyanocobalamin was conducted with 20 volunteers over a period of 14 consecutive days. Urine, plasma, and concentrated red blood cells were analyzed for their cobalt content. The samples were collected starting 7 days before the administration until 7 days after. Total Co concentrations were analyzed by using inductively coupled plasma mass spectrometry (ICP-MS), which yielded significantly elevated levels exclusively after inorganic cobalt intake. Furthermore, a liquid chromatography (LC)-ICP-MS approach was established and employed for the simultaneous determination of organically bound and inorganic cobalt by chromatographic separation within one single run. The analytical approach offers the option to further develop detection methods of illegal Co2+ supplementation in sport.

Excretion of 19-norandrosterone after consumption of boar meat.

The consumption of the offal of noncastrated pigs can lead to the excretion of 19-norandrosterone (NorA) in urine of humans. In doping control, GC/C/IRMS is the method of choice to differentiate between an endogenous or exogenous origin of urinary NorA. In some cases, after the consumption of wild boar offal, the δ13 C values of urinary NorA fulfill the criteria of an adverse analytical finding due to differing food sources of boar and consumer. However, consumption of wild boar's offal is not very common in Germany, and thus, the occurrence of such an analytical finding is unlikely. In contrast, the commerce with wild boar meat has increased in Germany within the last years. Up to 20,000 tons of wild boar meat are annually consumed. In order to probe for the probability of the occurrence of urinary NorA after consumption of wild boar meat, human urine samples were tested following the ingestion of commercially available game. In approximately half of the urine samples, traces of NorA were detected postadministration of 200 to 400 g boar meat. The highest urinary concentration was 2.9 ng/ml, and significant amounts were detected up to 9 h after the meal. δ13 C values ranged from -18.5‰ to -23.5‰, which would have led to at least two adverse analytical findings if the samples were collected in an antidoping context. IRMS analysis on German boar tissue samples showed that δ13 C values for wild boar's steroids are unpredictable and may vary seasonally.

The analytical approach for detection of carbamylated erythropoietin for doping control purposes.

Erythropoietin (EPO) has protective effects in several tissues and could be used for therapeutic purposes, but the doses of EPO that can be beneficial in case of hypoxic-ischemic conditions due to overinduced erythropoiesis could be detrimental in treated patients. Carbamylation of erythropoietin maintains the tissue-protective effects of EPO but without erythropoietic effects. Carbamylated EPO (CEPO) is listed in WADA Prohibited List in class S2 as "Innate repair receptor agonists." The CEPO was synthesized using the method described previously. Digestion with endoproteinase Lys-C was used to distinguish rhEPO from CEPO. The digested samples containing recombinant EPO, urinary EPO (uEPO), or CEPO were analyzed by the SAR-PAGE method (sarcosyl polyacrylamide gel electrophoresis-PAGE). Endoproteinase Lys-C breaks the peptide chains of lysine. Lysine residues, converted to homocitrulline by carbamylation, cannot be cleaved by endoproteinase Lys-C. Therefore, the CEPO protein chain remained unchanged in contrast to rhEPO and uEPO, which allows for easily differentiation of them.

Elimination profiles of microdosed ostarine mimicking contaminated products ingestion.

The possibility of nutritional supplement contamination with minute amounts of the selective androgen receptor modulator (SARM) ostarine has become a major concern for athletes and result managing authorities. In case of an adverse analytical finding (AAF), affected athletes need to provide conclusive information, demonstrating that the test result originates from a contamination scenario rather than doping. The aim of this research project was to study the elimination profiles of microdosed ostarine and characterize the time-dependent urinary excretion of the drug and selected metabolites. Single- and multi-dose administration studies with 1, 10, and 50 µg of ostarine were conducted, and collected urine samples were analyzed by LC-MS/MS following solid-phase extraction or enzymatic hydrolysis combined with liquid-liquid extraction. In the post-administration samples, both the maximum urine concentrations/abundance ratios and detection times of ostarine and its phase-I and phase-II metabolites were found to correlate with the administered drug dose. With regard to the observed maximum levels of ostarine, the time points of peak urinary concentrations/abundance ratios, and detection windows, a high inter-individual variation was observed. However, the study demonstrated that a single oral dose of as little as 1 µg can be detected for up to 9 (5) days by monitoring ostarine (glucuronide), and hydroxylated metabolites (especially M1a) appear to offer a considerably shorter detection window. The obtained data on ostarine (metabolite) detection times and urinary concentrations following different administration schemes support the interpretation of AAFs, in particular when scenarios of proven supplement contamination are discussed and supplement administration protocols exist.

Detection of follistatin-based inhibitors of the TGF-ß signaling pathways in serum/plasma by means of LC-HRMS/MS and Western blotting.

Cytokines of the transforming growth factor beta (TGF-ß) superfamily such as myostatin and activin A are considered as key regulators of skeletal muscle mass. In vivo, their activity is controlled by different binding proteins such as follistatin (FST), whose interaction with the circulating growth factors prevents activation of the activin type II receptors. FST-based protein therapeutics are therefore not only promising drug candidates for the treatment of muscular diseases but also potential performance-enhancing agents in sports. Within this study, two complementary detection assays for FST-based inhibitors of the TGF-ß signaling pathways in doping control serum and plasma samples were developed by using both monomeric FST and dimeric FST-Fc fusion proteins as model compounds. The initial testing procedure is based on immunoaffinity purification, tryptic digestion, and LC-HRMS/MS, offering high specificity by targeting tryptic signature peptides of FST. As the glycoprotein is also produced endogenously, the confirmation method employs immunoaffinity purification, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and Western blotting in order to detect the intact proteins and differentiate synthetic FST-Fc constructs from naturally occurring FST isoforms. Both assays were found to be highly specific with an estimated detection limit of 10 ng/ml. Moreover, a commercial sandwich enzyme-linked immunosorbent assay was used to determine endogenous FST values. The detected FST serum levels of healthy volunteers were found below 5 ng/ml, which is in accordance with reference values from the literature and below the doping control detection methods' limit of detection (LOD). The presented assays expand the range of available tests for emerging doping agents, and the initial testing procedure can readily be modified to include further protein drugs.

Implementation of the HIF activator IOX-2 in routine doping controls - Pilot study data.

Early in 2020, racehorse doping cases revolved around the hypoxia-inducible factor (HIF) activator IOX-2. While the composition of IOX-2 has also been known and monitored in human doping controls for several years, the testing capability of routine sports drug testing methods was revisited for this newly surfaced doping agent. IOX-2 and the analytically well-established HIF activator roxadustat (FG-4592) share identical precursor/product ion pairs, enabling their co-detection in existing initial testing procedures in routine doping controls for the intact unconjugated analytes. In addition, hydroxylated IOX-2 and the corresponding glucuronic acid conjugates were identified as major metabolites in a microdose elimination study, contributing to enhanced initial testing and confirmation procedures.

Detection of a nonerythropoietic erythropoietin, Neuro-EPO, in blood after intranasal administration in rat.

Nonerythropoietic erythropoietins (EPOs) are investigated for their high antioxidant properties. A new drug candidate under clinical investigation to treat brain diseases is Neuro-EPO, produced by selecting EPO isoforms with low sialic acid content. Intranasal administration allows to bypass the blood-brain barrier to get a fast and concentrated delivery to the brain. The aims of this project were to characterize Neuro-EPO with anti-doping methods used to detect conventional recombinant EPOs (isoelectric focusing [IEF] and sodium dodecyl sulfate-polyacrylamide gel electrophoresis [SDS-PAGE]) and to evaluate the window of detection of Neuro-EPO in brain and blood (plasma) after a single intranasal administration in rats. Neuro-EPO drug analyzed by IEF-PAGE presented a very basic profile completely detected only when using a 2-8 or 2-10 pH gradient instead of the conventional 2-6 pH gradient. Its profile consisted in six main bands that did not interfere with endogenous EPO profile from human or rat. After SDS-PAGE, a broad band was detected for Neuro-EPO in the same area as endogenous EPO, making Neuro-EPO identification very difficult by this approach. Therefore, IEF was the method for identification chosen after administration in rats. Neuro-EPO was clearly identified in blood 2 and 6 h after the delivery. Fainter signals were obtained between 12 and 48 h, but some characteristic very basic bands remained detectable. Surprisingly, brain extracts did not show the presence of Neuro-EPO even 2 h after administration, indicating a fast degradation or elimination from the brain to the bloodstream. This experiment indicated that detection of Neuro-EPO after intranasal delivery should be possible for a few days.

Is pain temporary and glory forever? Detection of tramadol using dried blood spot in cycling competitions.

Tramadol is a synthetic opioid drug used in the treatment of chronic and acute pain. An abnormal prevalence of its misuse in elite sport to overcome pain resulting from prolonged physical effort was recently reported. However, besides its antinociceptive effects, tramadol consumption is associated with negative effects such as numbness, confusion, and reduced alertness. This fact prompted the Union Cycliste Internationale to ban the use of tramadol in cycling competitions. Herein, we present the development of a dried blood spot (DBS) sample collection and preparation method followed by a liquid-chromatography mass spectrometry (LC-MS) analysis to rapidly determine the presence of tramadol and its two main metabolites in blood samples. The detection window of each analyte was evaluated and the analysis of performance on various MS platforms (HRMS and MS/MS) was assessed. Tramadol and its two main metabolites were detected up to 12 h after the intake of a single dose of 50 mg of tramadol in positive controls. In professional cycling competitions, 711 DBS samples collected from 361 different riders were analysed using the developed methodology, but all returned negative results (absence of parent and both metabolite compounds). In the context of professional cycling, we illustrate a valid method bringing together the easiness of collection and minimal sample preparation required by DBS, yet affording the performance standards of MS determination. The proposed method to detect tramadol and its metabolites was successfully implemented in cycling races with a probable strong deterrent effect.

Paper spray mass spectrometry - A potential complementary technique for the detection of polar compounds in sports drug testing.

In this proof-of-concept study, paper spray mass spectrometry was investigated as a high-throughput and fully automated technique for the initial testing of particularly polar compounds that are prohibited in sports. The technique allows the ionization of analytes from complex sample matrices such as blood and urine when spotted onto a paper strip. By minimizing sample preparation and omitting chromatographic separation, paper spray mass spectrometry benefits from considerable cost- and time-savings compared with conventional high performance liquid chromatography/tandem mass spectrometry, especially in cases where conventional reversed-phase liquid chromatography offers limited applicability. All but one of the investigated model compounds fulfilled the World Anti-Doping Agency's (WADA's) requirements regarding the applicable minimum required performance limits for initial testing procedures. In addition, the combination of paper spray mass spectrometry and ion mobility separation results in enhanced selectivity and sensitivity and is a particularly valuable analytical configuration.

Alternative markers for Methylnortestosterone misuse in human urine.

Methylnortestosterone is a progestin and synthetic androgenic anabolic steroid, prohibited by WADA. Methylnortestosterone misuse is commonly detected by monitoring the parent compound and its main metabolites, 17α-methyl-5α-estrane-3α, 17ß-diol (M1) and 17α-methyl-5ß-estrane-3α, 17ß-diol (M2), in the glucuronide fraction. In the current study, a direct detection of methylnortestosterone sulfo-conjugated metabolites after ethyl acetate extraction and analysis by LC/Q/TOF-MS in negative ionization mode was performed, detecting two main sulfate metabolites (S1, S2). For the characterization of metabolites, samples from the excretion study, were additionally analyzed by GC-MS, after solvolysis and per TMS derivatization. RT and MS data collected, were compared with RT and MS data from metabolites of 17z-methyl-5α/ß-estrane-3α/ß, 17z-diols structures with prefixed stereochemistry at 3 and 5 positions, synthesized through Grignard reaction from 19-noretiocholanolone, 19-norandrosterone and 19-norepiandrosterone. Confirmed sulfate metabolites were S1, 17α-methyl-5α-estrane-3α, 17ß-diol 3α sulfate (detected up to 72 h) and S2, 17α-methyl-5ß-estrane-3α, 17ß-diol 3α sulfate (detected up to 192 h). Furthermore, applying targeted analysis based on RT and MS data of the synthesized metabolites two additional metabolites M3, 17ß-methyl-5ß-estrane-3α, 17α-diol and M4, 17ß-methyl-5α-estrane-3α, 17α-diol were detected in the glucuronide fraction and one more metabolite (S3) 17ß-methyl-5ß-estrane-3α, 17α-diol was detected in the sulfate fraction in lower abundance until the end of the excretion study (192 h). Interestingly, S2 could also be detected after the direct analysis of non-hydrolyzed steroid by GC-MS/MS as artifact, following normal ProcIV anabolic steroid procedure and using diethylether as extraction solvent.

Evaluation of epiandrosterone as a long-term marker of testosterone use.

Identification and evaluation of long-term markers is crucial in prolonging the detection window for anabolic steroid abuse in sport. Recently, sulfoconjugated epiandrosterone was identified as a potential long-term marker for the abuse of certain endogenous anabolic agents, including testosterone, which continues to be widely used as a performance enhancing agent in sport. To evaluate the applicability of epiandrosterone sulfate as a marker for testosterone use, administration studies were conducted with multiple modes of testosterone administration - transdermal, intramuscular, and subcutaneous. A modified sample preparation method was used to collect both glucuronidated and sulfoconjugated analytes of interest. Carbon isotope ratio measurements from the administration studies are presented here. Epiandrosterone was less effective than the conventionally used target compounds for detection of the low dose application (transdermal gel). With intramuscular administration, epiandrosterone was more diagnostic than with transdermal administration, but it did not prolong the detection window more than the conventional target compounds. With subcutaneous administration, the doses administered to the subjects were varied and the effect on the epiandrosterone values was dependent on the magnitude of the dose administered. Epiandrosterone does not appear to be a useful marker in the detection of low dose testosterone administration. It is responsive to higher dose administration, but it does not provide an extension of the detection window relative to conventional target compounds.

Carbon isotopic characterization of prednisolone and prednisone pharmaceutical formulations: Implications in antidoping 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 δ13 C values, except for the Belgian nasal spray, Sofrasolone®, with a less depleted 13 C 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 δ13 C values. Urine samples were collected before, during, and within the 36 hours after the administration of the spray. Both δ13 C 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. δ13 C 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 δ13 C 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.