LC-MS/MS Tracking of Deflazacort Metabolites for Doping Control

Deflazacort (DEF) is a steroid drug that is banned in sports if taken orally. A joint study conducted by researchers at the Hospital del Mar Research Institute, Universitat Pompeu Fabra, and the University of Barcelona (all in Barcelona, Spain) tracked eight healthy men who each took a single 30 mg oral dose of DEF to determine how the drug and its breakdown products appeared in (and cleared from) their urine and blood, checking whether the World Anti-Doping Agency's (WADA) detection threshold of 30 ng/mL was sufficient to catch DEF use. Urine and plasma samples were collected before and after administration, and DEF and its metabolites were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). A paper based on this study was published in Drug Testing and Analysis.¹

Why is More Research Needed into How DEF is Processed and Cleared by the Body, Particularly in the Context of Anti-Doping?

DEF is a glucocorticoid, which are powerful drugs that fight inflammation and calm down the immune system. They're commonly prescribed for all sorts of health problems. In sports, athletes often use them to deal with everyday illnesses as well as injuries from training or competition.^2,3

As there is little detailed information available regarding how this drug gets flushed out in urine, the research team believes that there is a need for more studies to help with anti-doping checks and set proper limits for it. DEF is basically a starter version of the drug that gets soaked up fast after you take it, then quickly broken down in the blood into its active form, called 21-desacetyl-deflazacort (DES), and then turned into several inactive versions showing up in blood and urine.^4,5

How Does DEF and its Metabolites Behave in the Body After a Single Oral Dose?

The researchers report that tests on urine showed that DEF quickly breaks down into DES in the body, with almost none of the original DEF showing up unchanged. DES and two related forms (6βOHDES and 6αOHDES) appeared in most urine samples over the first two days after dosing. DES hit its peak early, in the first four hours, then dropped below 30 ng/mL after about a day. Meanwhile, 6βOHDES peaked a bit later, between four and eight hours, and stayed above 30 ng/mL for up to 36–48 hours. The 6αOHDES version showed up at lower levels and cleared out fast. In blood samples, DES and 6βOHDES showed up within eight hours, with DES reaching higher peaks and sticking around longer. No DEF was found in the blood at all. The models lined up well between the urine and blood results. Cortisol levels dropped after the dose, showing the drug was active throughout the body, but they bounced back by 72 hours in most people.¹

“The findings,” write the authors of the paper,¹ “support the use of DES as the primary urinary marker for DEF detection, confirm the suitability of the MRL of 30 ng/mL and support the recommendation of a 3-day washout period due to interindividual variability.”

While the results suggest that 48 hours might be enough time for DEF to clear the body after taking it by mouth, the research team pointed out that people metabolize drugs differently. Furthermore, the fact that blood data varied across different ethnic groups also hints that urine results might vary as well, which, in their opinion, is another reason to keep the more cautious approach.¹

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References

1. Coll, S.; Bressan, C.; Monfort, N. et al. Elimination Profile of Deflazacort and Metabolites in Urine and Plasma Following Oral Administration: Relevance to Sports Drug Testing. Drug Test Anal. 2026. DOI: 10.1002/dta.70093
2. Keller-Wood, M. E.; Dallman, M. F. Corticosteroid Inhibition of ACTH Secretion. Endocr Rev. 1984, 5 (1), 1-24. DOI: 10.1210/edrv-5-1-1
3. Henzen, C.; Suter, A.; Lerch, E. et al. Suppression and Recovery of Adrenal Response After Short-Term, High-Dose Glucocorticoid Treatment. Lancet 2000, 355 (9203), 542-545. DOI: 10.1016/S0140-6736(99)06290-X
4. Kong, R.; Ma, J.; Beers, B. et al. Metabolite V, an Epoxide Species is a Minor Circulating Metabolite in Humans Following a Single Oral Dose of Deflazacort. Pharmacol Res Perspect. 2020, 8 (6), e00677. DOI: 10.1002/prp2.677
5. Assandri, A.; Ferrari, P.; Perazzi, A. et al. Disposition and Metabolism of a New Steroidal Anti-Inflammatory Agent, Deflazacort, in Cynomolgus Monkeys. Xenobiotica 1983, 13 (3), 185-196. DOI: 10.3109/00498258309052253