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Featured researches published by Christopher J. Walker.


Drug Testing and Analysis | 2009

Counterfeiting in performance‐ and image‐enhancing drugs

Michael R. Graham; Paul Ryan; Julien S. Baker; Bruce Davies; Non-Eleri Thomas; Stephen-Mark Cooper; Peter Evans; Sue Easmon; Christopher J. Walker; David A. Cowan; Andrew T. Kicman

The current drastic escalation in obesity may be contributing to the exponential rise in drugs used for image enhancement. Drugs such as anabolic-androgenic steroids (AAS) are perceived as a viable method of achieving a perfect physique. They are also the most widely abused drugs in sport. The Internet has encouraged the abuse of expensive drugs, particularly human growth hormone (hGH), resulting in increased importation for personal use. The substantial increase in this market has opened up avenues for counterfeiting, estimated as a multi-million pound business. The acute adverse effects from contaminated vials may result in a variety of pathologies including communicable diseases. In 2007, in the UK, a series of intramuscular abscesses, requiring surgical treatment, led us to study samples obtained from the underground market. The analysis of 38 parenteral samples and 19 oral samples of tablets was performed by a World Anti-Doping Agency (WADA) accredited laboratory, in an attempt to establish the extent of available counterfeit products. Fifty-three per cent (20) of the injectable AAS esters and 21% (4) of the oral tablets were counterfeit. Culture and sensitivity revealed the presence of skin commensal organisms, which may have contributed to the development of the abscesses. Users of AAS and hGH for sport, including bodybuilding, are currently risking their health because of counterfeit and poorly controlled products.


Drug Testing and Analysis | 2015

Anabolic steroids detected in bodybuilding dietary supplements – a significant risk to public health

Vincenzo Abbate; Andrew T. Kicman; Michael Evans-Brown; Jim McVeigh; David A. Cowan; C Wilson; S J Coles; Christopher J. Walker

Twenty-four products suspected of containing anabolic steroids and sold in fitness equipment shops in the United Kingdom (UK) were analyzed for their qualitative and semi-quantitative content using full scan gas chromatography-mass spectrometry (GC-MS), accurate mass liquid chromatography-mass spectrometry (LC-MS), high pressure liquid chromatography with diode array detection (HPLC-DAD), UV-Vis, and nuclear magnetic resonance (NMR) spectroscopy. In addition, X-ray crystallography enabled the identification of one of the compounds, where reference standard was not available. Of the 24 products tested, 23 contained steroids including known anabolic agents; 16 of these contained steroids that were different to those indicated on the packaging and one product contained no steroid at all. Overall, 13 different steroids were identified; 12 of these are controlled in the UK under the Misuse of Drugs Act 1971. Several of the products contained steroids that may be considered to have considerable pharmacological activity, based on their chemical structures and the amounts present. This could unwittingly expose users to a significant risk to their health, which is of particular concern for naïve users.


The Journal of Steroid Biochemistry and Molecular Biology | 1992

Possible indices for the detection of the administration of dihydrotestosterone to athletes

G.J. Southan; R V Brooks; David A. Cowan; Andrew T. Kicman; N. Unnadkat; Christopher J. Walker

Dihydrotestosterone (DHT) can be used by an athlete as an anabolic steroid to evade the current International Olympic Committee approved drug tests. To investigate the possibility of a method for its detection, the heptanoate ester of DHT was administered to two male subjects (150 mg i.m.). Urine samples, collected before and after the injection, were subjected to enzymatic hydrolysis and the excretion rates of DHT, 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol) and testosterone (T) were determined by radioimmunoassay. Relative changes in the excretion of DHT, 3 alpha-diol, 5 alpha-androstane-3 beta,17 beta-diol (3 beta-diol), 5 beta-androstane-3 alpha, 17 beta-diol (5 beta-diol), T and epitestosterone (17 alpha hydroxyandrost-4-en-3-one; Epi-T) were determined by gas chromatography-mass spectrometry (GC-MS). Following administration of DHT, the urinary excretion rates of DHT, 3 alpha-diol and 3 beta-diol increased when compared to those of T, Epi-T, 5 beta-diol and luteinizing hormone (LH). Concentrations of DHT in the plasma increased whereas those of T, LH and follicle stimulating hormone decreased. The changes following such modest doses of DHT suggest that these ratios of urinary hormones may be used for the detection of doping with DHT.


Drug Testing and Analysis | 2015

Running an unknown risk: a marathon death associated with the use of 1,3-dimethylamylamine (DMAA).

John R. H. Archer; Paul I. Dargan; Alfonso Maria Lostia; Jon van der Walt; Katherine Henderson; Nicola Drake; Sanjay Sharma; David M. Wood; Christopher J. Walker; Andrew T. Kicman

Keywords: 1,3 dimethylamylamine (DMAA); sports supplement; Marathon; fatality; 4-methylhexane-2-amine; recreational drug


Steroids | 2009

Doping in sport--1. Excretion of 19-norandrosterone by healthy women, including those using contraceptives containing norethisterone.

Christopher J. Walker; David A. Cowan; Vivian H.T. James; Joanne C.Y. Lau; Andrew T. Kicman

19-Norandrosterone (19-NA) is the principal urinary metabolite of the anabolic steroid nandrolone and its prohormones. The administration of these 19-nor androgens is prohibited in sport by the World Anti-Doping Agency (WADA) but, even so, adverse findings for 19-NA continue to be commonly reported. Little is known about the urinary concentrations of 19-NA that can occur in women who are not using anabolic steroids, including those using oral contraceptives containing the 19-nor progestogen norethisterone. In 2004, WADA lowered the reporting threshold for 19-NA for females from 5 to 2ng/mL. The lack of any substantial data on 19-NA excretion in women prompted this large-scale investigation. In this investigation, single untimed urines collected from 1202 female volunteers, 38 of whom were taking norethisterone containing contraceptives, were analysed for 19-NA. None of the women was a competitive athlete and pregnancy had been excluded by a urinary test for human chorionic gonadotropin (hCG). Only one sample exceeded the 19-NA reporting threshold having a concentration of 4.1ng/mL. This sample was from a user of a norethisterone-containing contraceptive.


Steroids | 2009

Doping in sport—2. Quantification of the impurity 19-norandrostenedione in pharmaceutical preparations of norethisterone

Christopher J. Walker; David A. Cowan; Vivian H.T. James; Joanne C.Y. Lau; Andrew T. Kicman

The finding of measurable amounts of 19-norandrostenedione in norethisterone tablets prompted us to develop an assay to quantify this steroid. 19-Norandrostenedione is an anabolic steroid whose use in sport is prohibited by the World Anti-Doping Agency (WADA). The assay was developed using isotope dilution and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the quantification of 19-norandrostenedione in norethisterone formulations, with [3,4-(13)C(2)]-19-norandrostenedione as the internal standard. The results showed amounts up to 1.01+/-0.01microg (mean+/-S.E.M.) per tablet in those containing 5mg of norethisterone or norethisterone acetate (0.02%, w/w) and up to 0.5+/-0.01microg (mean+/-S.E.M.) per tablet (0.05%, w/w) in oral contraceptive tablets containing 0.35-1.5mg of norethisterone or norethisterone acetate. No tablet tested exceeded the British Pharmacopoeia limit of 0.1% for this impurity.


Steroids | 2009

Doping in sport: 3. Metabolic conversion of oral norethisterone to urinary 19-norandrosterone

Christopher J. Walker; David A. Cowan; Vivian H.T. James; Joanne C.Y. Lau; Andrew T. Kicman

The detection of 19 norandrosterone (19-NA) in a competitors urine sample is taken as prima facie evidence of administration of nandrolone or other 19-norsteroid but a potential problem is that administration of norethisterone, a progestogen used for menstrual disorders and for hormonal contraception, also results in the excretion of 19-NA that can exceed the laboratory reporting threshold of 2ng/mL. The contribution of norethisterone to urinary 19-NA with and without 19-norandrostenedione, a known norethisterone tablet impurity, requires evaluation. Preparations containing, either <2ng or 1microg 19-norandrostenedione impurity per 5mg of norethisterone, administered to female volunteers (n=10) in doses comparable to those used for menstrual disorders (5mg three times daily for 10 days), resulted in maximal 19-NA concentrations of 51 and 63ng/mL, respectively. The maximal concentration of 19-NA, 2h post-administration of a single 1microg dose of 19-norandrostenedione, was 2.4ng/mL. These results prove unequivocally that norethisterone is metabolized to 19-NA and that there is only a minor contribution from the impurity 19-norandrostenedione. Administration to women (n=30) of a single contraceptive tablet containing norethisterone (1mg) with one of the highest proportions of the impurity 19-norandrostenedione ( approximately 0.5microg, 0.05%, w/w) resulted in a urinary 19-NA concentration of 9.1ng/mL, with a maximum concentration ratio of 19-NA to the norethisterone metabolite 3alpha,5beta-tetrahydronorethisterone of 0.36. We provide data that should remove the need for time-consuming follow-up investigations to consider whether doping with 19-norandrogens has occurred.


Drug Testing and Analysis | 2017

Application of testosterone to epitestosterone ratio to horse urine - a complementary approach to detect the administrations of testosterone and its pro-drugs in Thoroughbred geldings

Marjaana Viljanto; James P. Scarth; Pamela Hincks; Lynn Hillyer; Adam T. Cawley; Craig J. Suann; Glenys Noble; Christopher J. Walker; Andrew T. Kicman; Mark C. Parkin

Detection of testosterone and/or its pro-drugs in the gelding is currently regulated by the application of an international threshold for urinary testosterone of 20 ng/mL. The use of steroid ratios may provide a useful supplementary approach to aid in differentiating between the administration of these steroids and unusual physiological conditions that may result in atypically high testosterone concentrations. In the current study, an ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was developed to quantify testosterone (T) and epitestosterone (E). The method was used to analyze 200 post-race urine samples from geldings in order to generate the ratios for the reference population. Following statistical analysis of the data, an upper limit of 5 for T:E ratio in geldings is proposed. Samples collected from 15 geldings with atypical urinary testosterone concentrations (>15 ng/mL) but otherwise normal steroid profile, had T:E ratios within those observed for the reference population. The applicability of an upper T:E ratio to detect an administration was demonstrated by the analysis of a selection of incurred samples from testosterone propionate, dehydroepiandrosterone (DHEA), and a mixture of DHEA and pregnenolone (Equi-Bolic®) administrations. These produced testosterone concentrations above the threshold of 20 ng/mL, but also T:E ratios above the proposed limit of 5. In conclusion, consideration of the T:E ratio appears to be a valuable complementary aid to evaluate whether an atypical testosterone concentration could be caused by a natural biological outlier as opposed to the administration of these steroids. Copyright


Drug Testing and Analysis | 2018

Potency of Δ9–tetrahydrocannabinol and other cannabinoids in cannabis in England in 2016: Implications for public health and pharmacology

David Potter; Kathy Hammond; Shaun Tuffnell; Christopher J. Walker; Marta Di Forti

In 2005 and 2008, studies reported that cannabis in England had become dominated by the sinsemilla (unseeded female) form. The average potency (Δ9 -tetrahydrocannabinol [THC] content) of this material had doubled over the previous decade. Cannabis resin then circulating contained approximately equal ratios of THC and cannabidiol (CBD), whereas sinsemilla was almost devoid of CBD. Despite raised health concerns regarding sinsemilla use and the development of psychotic disorders, no update on street cannabis potency has been published since 2008. A total of 995 seized cannabis samples were acquired from the same 5 constabulary areas included in the 2005 study. The differing forms were segregated, and a representative 460 samples analyzed to assess their cannabinoid content using gas chromatography. The resultant median sinsemilla potency of 14.2% THC was similar to that observed in 2005 (13.9%). In each case, sinsemilla contained minimal CBD. Compared with 2005, resin had significantly higher mean THC (6.3%) and lower CBD (2.3%) contents (p < 0.0001). Although the average THC concentration in sinsemilla samples across the 5 constabularies has remained stable since 2005, the availability of this potent form of cannabis has further increased. Moreover, the now rarer resin samples show significantly decreased CBD contents and CBD:THC ratios, leaving the United Kingdoms cannabis street market populated by high-potency varieties of cannabis, which may have concerning implications for public health.


BMJ | 2015

Potent and untested drugs sold as "dietary supplements".

Andreas Kimergård; Christopher J. Walker; David A. Cowan

A new challenge to public health has recently emerged from potent and untested drugs being sold under the guise of “dietary” supplements.1 2 3 4 Fuelled by growing demand for products promising a better body, enhanced performance, and increased wellbeing, this trend highlights creative marketing strategies used in the illicit supply of drugs. Nine supplements suspected of containing drugs were analysed as part of an investigation for the television programme Spotlight …

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S.K. Tee

King's College London

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