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.

The authors have retracted this article [1] because after publication they became aware that the equine urine samples analysed for loxoprofen in this study were in fact equine plasma samples. Therefore the results and conclusions of this article cannot be relied upon. All authors agree to this retraction.

Objective: Suicide has recently become an important social problem. Thus, we analyzed prescription drugs that cause suicidal ideation. Methods: Of 156 drugs on the the Minister of Food and Drug Safty (MFDS) EZ-Drug site that had "suicide" listed as a side effect, 78 had "suicide" listed as a warning or contraindication; those 78 drugs were analyzed using data from the 2016 Health Insurance and Review and Assessment Services National Patient Sample (HIRA-NPS). Results: 51 "suicide risk" drugs was identified. Of all patients, 5.2% had received such drugs. The prescription rate was 0.8% of all prescriptions, accounting for 1.6% of all prescription days. From logistic regression analysis, the prescription rate for the drugs was approximately 1.1 times higher for women than for men. With regard to age, the prescription rate for patients 66 years and older was 15.5 times higher than those for patients 25-years and lower. With regard to medical departments, the prescription rates in psychiatry and dermatology departments were 8.1 times higher and 0.6 times lower than those in internal medicine departments, respectively. With regard to region, the prescription rates in Daegu and Jeju were 1.3 times higher and 0.79 times lower than those in Seoul, respectively. Conclusion: Drug-induced suicidal behavior is possible, and therefore efforts are needed to prevent it.