Archives of Pharmacal Research

, Volume 41, Issue 4, pp 459–466 | Cite as

RETRACTED ARTICLE: Analysis of loxoprofen in tablets, patches, and equine urine as tert-butyldimethylsilyl derivative by gas chromatography-mass spectrometry

  • Youngbae Kim
  • Chan Seo
  • Suin Oh
  • Juhwan Kwak
  • Sumin Jung
  • Eunsu Sin
  • Hyunbin Kim
  • Moongi Ji
  • Hyeon-Seong Lee
  • Hyung-Jin Park
  • Gwang Lee
  • Jundong Yu
  • Minsoo Kim
  • Wonjae LeeEmail author
  • Man-Jeong PaikEmail author
Research Article


Loxoprofen is a non-steroidal anti-inflammatory drug of the 2-arylpropionic acid type, which has used to treat musculoskeletal disorders in the horse racing industry. However, it has also used illicitly to mask clinical signs of inflammation and pain in racehorses. Thus, its accurate analysis has become an important issue in horse doping laboratories. In this study, an analytical method of loxoprofen was developed as tert-butyldimethylsilyl (TBDMS) derivative by gas chromatography-mass spectrometry (GC–MS). Characteristic fragment ions of [M-15], [M-57], and [M-139] permitted the accurate and selective detection of loxoprofen. Under optimal conditions, this method showed good linearity (r ≥ 0.999) in the range of 10–500 ng/mL, repeatability (% relative standard deviation = 5.6–8.5), and accuracy (% relative error = − 0.3–0.9) with a detection limit of 1.0 ng. When applied to the analysis of loxoprofen in tablet and patch products, loxoprofen was positively identified as TBDMS derivative by GC–MS. The present method provided rapid and accurate determination of loxoprofen in patch and tablet products. Levels of loxoprofen were highest in equine urine at 0.5 and 1 h after oral administration with single dose (3 mg/kg) to three horses, and then rapidly reduced to below the lower limit of quantification at 24 h. Therefore, the present method will be useful for the pharmacokinetic study and doping tests for loxoprofen and other similar acidic drugs in horses.


Loxoprofen tert-Butyldimethylsilyl derivative Gas chromatography-mass spectrometry Tablet Patch Equine urine 



This paper was supported by Sunchon National University Research Fund in 2016.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© The Pharmaceutical Society of Korea 2018

Authors and Affiliations

  1. 1.College of Pharmacy and Research Institute of Life and Pharmaceutical SciencesSunchon National UniversitySuncheonRepublic of Korea
  2. 2.Department of Physiology and Department of Biomedical SciencesAjou University School of MedicineSuwonRepublic of Korea
  3. 3.Racing LaboratoryKorea Racing AuthorityGwacheonRepublic of Korea
  4. 4.Jeonbuk Branch Institute, Korea Research Institute of Bioscience and BiotechnologyJeonbukRepublic of Korea
  5. 5.College of PharmacyChosun UniversityGwangjuRepublic of Korea

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