IV-040 Paul Thoueille

Pharmacometrics-based analysis of salmeterol and its metabolite α-hydroxysalmeterol in plasma and urine: practical implications for doping control

Paul Thoueille1,2, Anne Danion3, Morten Hostrup4, Michael Petrou5, Koen Deventer6, Thierry Buclin1, François R. Girardin1,2, Irene Mazzoni3, Monia Guidi1,7,8

1 Service of Clinical Pharmacology, Department of Medicine, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland. 2 Laboratory of Clinical Pharmacology, Department of Laboratory Medicine and Pathology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland. 3 Science and Medicine Department, World Anti-Doping Agency, Montreal, Quebec, Canada 4 Department of Nutrition, Exercise and Sports, The August Krogh Section for Human Physiology, University of Copenhagen, Copenhagen, Denmark. 5 Cyprus Anti-Doping Authority, Makarion Athletic Centre Avenue, Engomi, CY 2400, Nicosia, Cyprus. 6 Doping Control Laboratory (DoCoLab), Ghent University, Department of Diagnostic Sciences (GE32), Ottergemsesteenweg 460, B-9000 Ghent, Belgium. 7 Centre for Research and Innovation in Clinical Pharmaceutical Sciences, Lausanne University Hospital and University of Lausanne, Switzerland. 8 Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, University of Lausanne, Switzerland.

Introduction: Salmeterol is a commonly used β2-agonist included on the List of Prohibited Substances and Methods of the World Anti-Doping Agency (WADA) with a specified dosing limit of 200 µg in any 24h period via inhaled administration.1 An urine concentration minimum reporting level (MRL) of 10 ng/mL currently suggests a potential misuse/doping.2 The aim of this study was to provide the basis for evaluating the ability of the current WADA approach to discriminate between the permitted and prohibited use of salmeterol. To this end, we developed a population pharmacokinetic (popPK) model describing the PK of salmeterol in plasma and in urine after inhalation. We also assessed the PK of its major metabolite, α-hydroxysalmeterol, as salmeterol is extensively metabolized and only accounts for less than 5% of the excreted dose in urine.3

Methods: A total of 1175 concentrations (275 and 398 for salmeterol and 185 and 317 for α-hydroxysalmeterol in plasma and urine, respectively) measured in 92 individuals were obtained from five published4-8 and one unpublished studies. A stepwise procedure (NONMEM) was used to identify the model fitting best the concentrations in both matrices. Urine concentrations were corrected using the urine specific gravity (SG) when available (76 individuals) in accordance with the WADA technical document.9 Because urine volumes were only recorded for 17 subjects, a separate urine compartment was defined to approximate physiologic micturition assuming constant urine production to fit the urine concentrations by dividing drug/metabolite amounts by the volume produced in the corresponding period.10 Multiple levels of random effects (i.e., separate residual errors, individual and study-level between-subject variabilities (BSV)11) were tested. Because the studies included heterogeneous types of individuals (i.e., healthy, chronic asthmatics or athletes/trained individuals), this information was tested for significance on the base PK parameters and incorporated during model development. Finally, model-based Monte Carlo simulations, accounting for both BSV and residual errors, were performed to evaluate the impact of different dosing regimens administered every 12h (BID) (i.e., therapeutic doses: 50 µg and 100 µg, i.e., the maximum dose authorized;1 doping doses: 200 µg and 400 µg) for one week on salmeterol urine concentrations. 

Results: A two-compartment model (i.e., V1 and V2 for the central and peripheral compartments, respectively) assuming intravenous-like bolus absorption kinetics best depicted plasma salmeterol PK, in accordance with previous observations.12 A complete plasma conversion of salmeterol into α-hydroxysalmeterol was assumed (k13),3 while urinary excretion constant rates of salmeterol (k14) and its metabolite (k35) from their respective plasma compartments were described separately. Parameter estimates of the final popPK model with BSV (CV%) were: V1 of 384 L (16.9%), inter-compartmental clearance of 1510 L/h (70.7%), V2 of 907 L (41.4%), salmeterol plasma clearance (CLS) of 188 L/h (29.5%), k13 of 0.292 h-1 (40.4%), α-hydroxysalmeterol plasma clearance of 199 L/h, k14 of 0.00106 h-1 (28.6%), k35 of 0.0168 h-1, and urine production of 0.0775 L/h (73.8% for SG-uncorrected urine concentrations). Athletes/trained individuals had a 66% higher CLS and a 191% increased k14 compared to other subjects, resulting in significantly higher salmeterol urine concentrations. Distinct proportional residual errors per compartment were estimated and combined when found to be similar between studies, while study-level BSV did not improve the fit. Simulations indicated that in a urine sample collected 1 hour after the last inhalation, salmeterol concentrations above the MRL would only be expected in 1.5% and 17.4% of cases after dosing of 200 µg and 400 µg BID, respectively. However, in a sample collected 4 hours post-dose, the probability of detecting salmeterol concentrations above the MRL would be 0.9% after 400 µg BID. 

Conclusion: The MRL for salmeterol in urine is not expected to detect salmeterol concentrations in urine at therapeutic doses. Future analyses will determine if the MRL is surpassed using different combinations of the maximal authorized dose of 200 µg within 24h. Finally, our popPK model suggests that the current MRL could be lowered to correctly evaluate suspected cases of doping.

References:

  1. World Anti-Doping Agency. The Prohibited List. Available from: https://www.wada-ama.org/en/prohibited-list#search-anchor.
  2. WADA. Minimum required performance levels and applicable minimum reporting levels for non-threshold substances analyzed by chromatographic – mass spectrometric analytical methods. WADA Technical Document – TD2022MRPL: World Anti-Doping Agency, 2022.
  3. Cazzola M, Testi R, Matera MG. Clinical Pharmacokinetics of Salmeterol. Clinical pharmacokinetics 2002; 41(1): 19-30.
  4. Jacobson GA, Hostrup M. The salmeterol anomaly and the need for a urine threshold. Drug Testing and Analysis 2022; 14(6): 997-1003.
  5. Jessen S, Becker V, Rzeppa S, et al. Pharmacokinetics of salmeterol and its main metabolite α-hydroxysalmeterol after acute and chronic dry powder inhalation in exercising endurance-trained men: Implications for doping control. Drug Testing and Analysis 2021; 13(4): 747-61.
  6. Jacobson GA, Hostrup M, Narkowicz CK, Nichols DS, Haydn Walters E. Enantioselective disposition of (R)-salmeterol and (S)-salmeterol in urine following inhaled dosing and application to doping control. Drug Test Anal 2017; 9(8): 1262-6.
  7. Hostrup M, Kalsen A, Elers J, et al. Urine concentrations of inhaled salmeterol and its metabolite alpha-hydroxysalmeterol in asthmatic and non-asthmatic subjects. Journal of Sports Medicine & Doping Studies 2012; 2(2).
  8. Deventer K, Pozo OJ, Delbeke FT, Van Eenoo P. Quantitative detection of inhaled salmeterol in human urine and relevance to doping control analysis. Ther Drug Monit 2011; 33(5): 627-31.
  9. WADA. Decision limits for the confirmatory quantification of exogenous threshold substances by chromatography-based analytical methods. WADA Technical Document – TD2022DL: World Anti-Doping Agency, 2022.
  10. Courlet P, Buclin T, Biollaz J, Mazzoni I, Rabin O, Guidi M. Model-based meta-analysis of salbutamol pharmacokinetics and practical implications for doping control. CPT: pharmacometrics & systems pharmacology 2022; 11(4): 469-81.
  11. van Wijk RC, Imperial MZ, Savic RM, Solans BP. Pharmacokinetic analysis across studies to drive knowledge-integration: A tutorial on individual patient data meta-analysis (IPDMA). CPT: pharmacometrics & systems pharmacology 2023; 12(9): 1187-200.
  12. Soulele K, Macheras P, Silvestro L, Rizea Savu S, Karalis V. Population pharmacokinetics of fluticasone propionate/salmeterol using two different dry powder inhalers. Eur J Pharm Sci 2015; 80: 33-42.

Reference: PAGE 32 (2024) Abstr 10947 [www.page-meeting.org/?abstract=10947]

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