Quantitative assessment of caffeine partial clearances in man.

Lelo, Aznan; Miners, John O.; Robson, RA; Birkett, D. J.

doi:10.1111/j.1365-2125.1986.tb05247.x

Cited by 120 publications

(63 citation statements)

References 11 publications

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“…Corresponding values for paraxanthine were 4.1% and 4.1%. Parax-'Copies of the SSQ may be obtained from Jack E. James. anthine was measured because (a) it is the principal metabolic product of caffeine (Lelo et al, 1986b), (b) it correlates better with observed caffeine intake than other major demethylated metabolites (theobromine, theophylline) (Lelo et al, 1986a), and (c) it has been found to produce slightly better correlations with diary records than those produced by plasma caffeine . The last of these findings is consistent with evidence concerning the pharmacokinetics of caffeine and paraxanthine.…”

Section: Saliva Assaysmentioning

confidence: 99%

Self‐report reliability and symptomatology of habitual caffeine consumption.

James

Bruce

Lader

et al. 1989

Brit J Clinical Pharma

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1 A large body of research on the demography of caffeine use and its potential health consequences has been undermined by the absence of empirical data on the reliability of retrospective self-reports of caffeine consumption. 2 The principal aim of the present study was to use standard bioanalytic methods to assess the reliability of subjects' self-reported caffeine use. Saliva samples were obtained from 142 first-and second-year medical students and assayed for caffeine and paraxanthine. 3 Self-reported caffeine use was found to be significantly correlated with salivary caffeine (r = 0.31, P < 0.001) and paraxanthine (r = 0.42, P < 0.001), thereby providing qualified support for the use of questionnaires to estimate patterns of caffeine consumption. 4 A secondary aim of the study was to extend previous research concerning the symptomatology of caffeine use by examining the association between caffeine exposure and a variety of measures of somatic and psychological health. Caffeine consumption was reliably associated with the self-reported occurrence of somatic symptoms, but not psychological well-being.

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Section: Saliva Assaysmentioning

confidence: 99%

Self‐report reliability and symptomatology of habitual caffeine consumption.

James

Bruce

Lader

et al. 1989

Brit J Clinical Pharma

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“…Both 1MX and 3-methylxanthine (3MX) are formed as References primary metabolites from theophylline but only 1MX is thine [5] which is demethylated further to 1MX and …”

Section: Discussionmentioning

confidence: 99%

“…procedure of Lelo et al [7]. Plasma allopurinol and oxypurinol concentrations were similarly measured by h.p.l.c.…”

Section: Analyticalmentioning

confidence: 99%

“…Moreover, baseline 1MX concentrations in urine are difficult to measure following theophylline administration due to almost complete conversion of 1MX to 1MU [4]. Protocol 1MX is also produced as a secondary metabolic product of Subjects took caffeine 75 mg 8 hourly administered as instant caffeine via 7-demethylation of the primary metabolite coffee ( preweighed) in 100 ml of hot water (with or without paraxanthine [5,6]. In the present study we have investigated milk and sugar) over a 7 day period.…”

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confidence: 99%

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1‐Methylxanthine derived from caffeine as a pharmacodynamic probe of oxypurinol effect

Birkett

Miners

Valente

et al. 1997

Brit J Clinical Pharma

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Aims In the present study we have investigated the use of caffeine, administered in the form of instant coffee, as a prodrug for 1MX to validate the use of the 1MU51MX ratio following caffeine administration as a pharmacodynamic measure of oxypurinol effect on xanthine oxidase. Methods Five healthy volunteers took caffeine 75 mg 8 hourly administered as instant coffee over a 7 day period. They were given allopurinol 600 mg on day 4. Urine was collected in 8 h aliquots from day 1-day 7. The ratio of 1-methyluric acid (1MU) to 1-methylxanthuric (1MX) was determined. Results The relationship between the plasma oxypurinol (the active metabolite of allopurinol) concentration at the midpoint of each caffeine dosage interval and the decrement in the urinary 1MX to 1MU ratio fitted well by a sigmoid E max model. Mean (±s.d.) values of the oxypurinol EC 50 (3.9±1.4 mg l −1 ), EC 90 (8.7±1.8 mg l −1 ) and the exponent, n (3.0±1.2) were similar to those obtained previously following either the direct administration of 1MX or the use of theophylline as a prodrug for 1MX. Conclusions These data indicate that the use of caffeine as a source of 1MX could provide a simple and ethically acceptable method for monitoring oxypurinol effect in patients taking allopurinol for the treatment of gout.Keywords: 1-methylxanthine, caffeine, allopurinol, oxypurinol, xanthine oxidase, pharmacodynamics ratio following caffeine administration as a pharmacodynamic Introduction measure of oxypurinol effect on xanthine oxidase. This would form the basis of a simple and ethically acceptable The hypouricaemic action of allopurinol and its active metabolite oxypurinol is due to direct inhibition of xanthine clinical test using dietary caffeine intake as the source of 1MX. oxidase and to an indirect negative feedback on the rate limiting enzyme for purine synthesis, PRPP synthase. We Methods have shown previously that the extent of inhibition of xanthine oxidase by oxypurinol (the major inhibitory species Subjects present during allopurinol dosing) can be assessed using the ratio of 1-methyluric acid (1MU) to 1-methylxanthine The subjects were five healthy volunteers, two male and (1MX) in urine [1][2][3]. In two of these studies [1, 2] 1MX three female, aged 24 to 32 years and weighing 53 kg to was administered intravenously, and in the other [3] 1MX 82 kg. Six subjects began the study but one was excluded was derived from theophylline administered as a 'prodrug'.because of protocol violations. The subjects were healthy as 1MX is not available as an approved drug product and must assessed by medical examination and standard laboratory be administered intravenously due to poor oral absorption.parameters. Each gave written informed consent to particiThe use of theophylline as a prodrug for 1MX required that pate in the study which was approved by the institutional subjects undertake a methylxanthine (caffeine) free diet.ethical review committee of St Vincent's Hospital. Moreover, baseline 1MX concentrations in urine are difficult to measure following...

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“…Through these literature searches the applicant identified a total of 37 publications as being pertinent to the health claim: 10 human intervention studies (Kuznicki and Turner, 1986;Lieberman et al, 1987a;Griffiths et al, 1990;Silverman and Griffiths, 1992;Mumford et al, 1994;Smith et al, 1999;Smit and Rogers, 2000;Van Dongen et al, 2001;Wyatt et al, 2004;Smith, 2009), 15 human studies on bioavailability or mechanistic studies (Marks and Kelly, 1973;Newton et al, 1981;Bonati et al, 1982;Blanchard and Sawers, 1983;Lelo et al, 1986;Nehlig et al, 1992;Liguori et al, 1997;Fredholm et al, 1999;Magkos and Kavouras, 2005;Specterman et al, 2005;Seng et al, 2009Seng et al, , 2010Arnaud, 2011;Perera et al, 2011;Smith et al, 2013), and 12 non-human studies (Bunker and McWilliams, 1979;Arnaud, 1985;Schiffmann et al, 1991;Okada et al, 1996;Ledent et al, 1997;Wang and Lau, 1998;El Yacoubi et al, 2000;Fredholm et al, 2001;Yamato et al, 2002;Liu and Gao, 2007;Costa et al, 2008;Botton et al, 2010). The applicant also provided four human intervention studies (Rogers, 2011, unpublished;Smith et al, 2011, unpublished;Kennedy, 2011...…”

Section: Scientific Substantiation Of the Claimed Effectmentioning

confidence: 99%

Scientific Opinion on the substantiation of a health claim related to caffeine and increased alertness pursuant to Article 13(5) of Regulation (EC) No 1924/2006

Products¹

2014

EFS2

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Following an application from SmithKline Beecham Limited, submitted for authorisation of a health claim pursuant to Article 13(5) of Regulation (EC) No 1924No /2006 via the Competent Authority of United Kingdom, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver an opinion on the scientific substantiation of a health claim related to caffeine and increased alertness. The food constituent, caffeine, which is the subject of the health claim, is sufficiently characterised. Increased alertness might be a beneficial physiological effect. A claim on caffeine and increased alertness, in the general adult population, for products containing at least 75 mg of caffeine per serving, has already been assessed by the Panel with a favourable outcome. In the present application, the applicant proposed that, in order to bear the claim, a product should contain at least 40 mg of caffeine per serving. In weighing the evidence, the Panel took into account that most studies which measured reaction time in various cognitive tasks found no effect of caffeine at doses < 75 mg. In the particular dose range between 40 and < 75 mg, no effect of caffeine was found on the majority of outcome measures of reaction time. The Panel notes that the majority of studies with caffeine doses of 75 mg or higher showed a significant reduction in measures of reaction time. On the basis of the evidence provided, the Panel reiterates its previous conclusion that, in order to bear the claim, a product should contain at least 75 mg caffeine per serving. The Panel concludes that a cause and effect relationship has not been established between the consumption of caffeine and increased alertness under the conditions of use proposed by the applicant. The scope of the application was proposed to fall under a health claim based on newly developed scientific evidence. The application included a request for the protection of proprietary data.The food constituent that is the subject of the health claim is caffeine, which is a well characterised food constituent and is measurable in foods by established methods. The Panel considers that caffeine is sufficiently characterised.The claimed effect proposed by the applicant is "helps to increase alertness". The target population proposed by the applicant is "the general adult population". Alertness is a well defined construct and can be measured by validated psychometric cognitive tests (e.g. simple reaction time tasks, choice reaction time tasks, and other vigilance tasks measuring reaction time). The Panel considers that increased alertness might be a beneficial physiological effect.A claim on caffeine and increased alertness, in the general adult population, for products containing at least 75 mg of caffeine per serving, has already been assessed by the Panel with a favourable outcome. The conclusion from the Panel was based on the evidence provided by consensus opinions/reports, and by the majority of the studies submitted for the scientific substantiation of the claim, w...

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Quantitative assessment of caffeine partial clearances in man.

Cited by 120 publications

References 11 publications

Self‐report reliability and symptomatology of habitual caffeine consumption.

Self‐report reliability and symptomatology of habitual caffeine consumption.

1‐Methylxanthine derived from caffeine as a pharmacodynamic probe of oxypurinol effect

Scientific Opinion on the substantiation of a health claim related to caffeine and increased alertness pursuant to Article 13(5) of Regulation (EC) No 1924/2006

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