Dose-dependent pharmacokinetics and psychomotor effects of caffeine in humans

Pharmacokinetic, pharmacological, and genotoxic evaluation of deuterated caffeine

Altering caffeine's negative physiological effects and extending its duration of activity is an active area of research; however, deuteration as a means of achieving these goals is unexplored. Deuteration substitutes one or more of the hydrogen atoms of a substance with deuterium, a stable isotope of hydrogen that contains an extra neutron. Deuteration can potentially alter the metabolic profile of a substance, while maintaining its pharmacodynamic properties. d9-Caffeine is a deuterated isotopologue of caffeine with the nine hydrogens contained in the 1, 3, and 7 methyl groups of caffeine substituted with deuterium. d9-Caffeine may prove to be an alternative to caffeine that may be consumed with less frequency, at lower doses, and with less exposure to downstream active metabolites of caffeine. Characterization of d9-caffeine's genotoxic potential, pharmacodynamic, and pharmacokinetic behavior is critical in establishing how it may differ from caffeine. d9-Caffeine was non-genotoxic with and without metabolic activation in both a bacterial reverse mutation assay and a human mammalian cell micronucleus assay at concentrations up to the ICH concentration limits. d9-Caffeine exhibited a prolonged systemic and brain exposure time in rats as compared to caffeine following oral administration. The adenosine receptor antagonist potency of d9-caffeine was similar to caffeine.

Dose-Response of Paraxanthine on Cognitive Function: A Double Blind, Placebo Controlled, Crossover Trial

Paraxanthine (PXN) is a metabolite of caffeine that has recently been reported to enhance cognition at a dose of 200 mg. Objective: To determine the acute and short-term (7-day) effects of varying doses of PXN on cognitive function and side effects. Methods: In a double blind, placebo-controlled, crossover, and counterbalanced manner, 12 healthy male and female volunteers (22.7 ± 4 years, 165 ± 7 cm, 66.5 ± 11 kg, 24.4 ± 3 kg/m²) ingested 200 mg of a placebo (PLA), 50 mg of PXN (ENFINITY™, Ingenious Ingredients, L.P.) + 150 mg PLA, 100 mg PXN + 100 mg PLA, or 200 mg of PXN. With each treatment experiment, participants completed side effect questionnaires and donated a fasting blood sample. Participants then performed a series of tests assessing cognition, executive function, memory, and reaction time. Participants then ingested one capsule of PLA or PXN treatments. Participants then completed side effects and cognitive function tests after 1, 2, 3, 4, 5, and 6 h of treatment ingestion. Participants continued ingesting one dose of the assigned treatment daily for 6-days and returned to the lab on day 7 to donate a fasting blood sample, assess side effects, and perform cognitive function tests. Participants repeated the experiment while ingesting remaining treatments in a counterbalanced manner after at least a 7-day washout period until all treatments were assessed. Results: The Sternberg Task Test (STT) 4-Letter Length Present Reaction Time tended to differ among groups (p = 0.06). Assessment of mean changes from baseline with 95% CI’s revealed several significant differences among treatments in Berg-Wisconsin Card Sorting Correct Responses, Preservative Errors (PEBL), and Preservative Errors (PAR Rules). There was also evidence of significant differences among treatments in the Go/No-Go Task tests in Mean Accuracy as well as several time points of increasing complexity among STT variables. Finally, there was evidence from Psychomotor Vigilance Task Test assessment that response time improved over the series of 20 trials assessed as well as during the 6-h experiment in the PXN treatment. Acute and short-term benefits compared to PLA were seen with each dose studied but more consistent effects appeared to be at 100 mg and 200 mg doses. No significant differences were observed among treatments in clinical chemistry panels or the frequency or severity of reported side effects. Results provide evidence that acute ingestion of 100 mg and 200 mg of PXN may affect some measures of cognition, memory, reasoning, and response time as well as help sustain attention. Additionally, that acute and daily ingestion of PXN for 7 days is not associated with any clinically significant side effects. Conclusions: PXN may serve as an effective nootropic agent at doses as low as 50 mg.

Effects of Caffeine and Caffeinated Beverages in Children, Adolescents and Young Adults: Short Review

The prevalence of ED consumption has increased over the past 10–15 years. Studies describing the effects of caffeine and caffeinated beverages show confusing results, so it seems important to regularly summarize the available facts, and in more detail. By a thorough analysis of more than 156 scientific papers, the authors describe the molecular background of absorption, as well as the positive and negative effects of different dosages of caffeine, just like its effects in physical activity and performance. ED and EDwA consumption is a regular habit of not only adults, but nowadays even of children and adolescents. There are no safe dosages described of caffeine or ED consumption for children. There are no positive short- or long-term effects of these compounds/products concerning developing brain functions, psycho-motor functions, or social development. Instead, there are many unpleasant side effects, and symptoms of regular or higher-dose ED consumption, especially at younger ages. This mini review describes many details of these unpleasant side effects, their severity, and motivations for consuming these compounds/products. In a quantitative research in Hungary (10–26 years, mean age: 15.6 ± 3.8 y, 1459 subjects, randomly chosen population), a survey based on a questionnaire asking people about their ED consumption habits was conducted. According to the data, 81.8% of the participants consumed EDs at least once, and 63.3% tried several products of the kind. A positive correlation was found between age and consumption (p < 0.001). The results show that a high proportion of this group often consumed EDwA, in many cases leading to harmful side-effects of caffeine overdose. In a sample of Hungarian high school and college students (17–26 years), ED consumption matched the international data, and only 19.7% of respondents did not use EDs at all (had never tasted an ED in their life).

Sport supplements and the athlete's gut: a review

Vigorous or prolonged exercise poses a challenge to gastrointestinal system functioning and is associated with digestive symptoms. This narrative review addresses 1) the potential of dietary supplements to enhance gut function and reduce exercise-associated gastrointestinal symptoms and 2) strategies for reducing gastrointestinal-related side effects resulting from popular sports supplements. Several supplements, including probiotics, glutamine, and bovine colostrum, have been shown to reduce markers of gastrointestinal damage and permeability with exercise. Yet, the clinical ramifications of these findings are uncertain, as improvements in symptoms have not been consistently observed. Among these supplements, probiotics modestly reduced exercise-associated gastrointestinal symptoms in a few studies, suggesting they are the most evidenced-based choice for athletes looking to manage such symptoms through supplementation. Carbohydrate, caffeine, and sodium bicarbonate are evidence-based supplements that can trigger gastrointestinal symptoms. Using glucose-fructose mixtures is beneficial when carbohydrate ingestion is high (>50 g/h) during exercise, and undertaking multiple gut training sessions prior to competition may also be helpful. Approaches for preventing caffeine-induced gastrointestinal disturbances include using low-to-moderate doses (<500 mg) and avoiding/minimizing exacerbating factors (stress, anxiety, other stimulants, fasting). Adverse gastrointestinal effects of sodium bicarbonate can be avoided by using enteric-coated formulations, low doses (0.2 g/kg), or multi-day loading protocols.

Acute Paraxanthine Ingestion Improves Cognition and Short-Term Memory and Helps Sustain Attention in a Double-Blind, Placebo-Controlled, Crossover Trial

This study examined the effects of acute paraxanthine (PXN) ingestion on markers of cognition, executive function, and psychomotor vigilance. In a randomized, double blind, placebo-controlled, crossover, and counterbalanced manner, 13 healthy male and female participants were randomly assigned to consume a placebo (PLA) or 200 mg of PXN (ENFINITY™, Ingenious Ingredients, L.P.). Participants completed stimulant sensitivity and side effect questionnaires and then performed the Berg Wisconsin Card Sorting Test (BCST), the Go/No-Go test (GNG), the Sternberg task test (STT), and the psychomotor vigilance task test (PVTT). Participants then ingested one capsule of PLA or PXN treatment. Participants completed side effect and cognitive function tests after 1, 2, 3, 4, 5, and 6 h after ingestion of the supplement. After 7 days, participants repeated the experiment while consuming the alternative treatment. Data were analyzed by general linear model (GLM) univariate analyses with repeated measures using body mass as a covariate, and by assessing mean and percent changes from baseline with 95% confidence intervals (CIs) expressed as means (LL, UL). PXN decreased BCST errors (PXN −4.7 [−0.2, −9.20], p = 0.04; PXN −17.5% [−36.1, 1.0], p = 0.06) and perseverative errors (PXN −2.2 [−4.2, −0.2], p = 0.03; PXN −32.8% [−64.4, 1.2], p = 0.04) at hour 6. GNG analysis revealed some evidence that PXN ingestion better maintained mean accuracy over time and Condition R Round 2 response time (e.g., PXN −25.1 [−52.2, 1.9] ms, p = 0.07 faster than PLA at 1 h), suggesting better sustained attention. PXN ingestion improved STT two-letter length absent and present reaction times over time as well as improving six-letter length absent reaction time after 2 h (PXN −86.5 ms [−165, −7.2], p = 0.03; PXN −9.0% [−18.1, 0.2], p = 0.05), suggesting that PXN enhanced the ability to store and retrieve random information of increasing complexity from short-term memory. A moderate treatment x time effect size (η_p² = 0.08) was observed in PVTT, where PXN sustained vigilance during Trial 2 after 2 h (PXN 840 ms [103, 1576], p = 0.03) and 4 h (PXN 1466 ms [579, 2353], p = 0.002) compared to PL. As testing progressed, the response time improved during the 20 trials and over the course of the 6 h experiment in the PXN treatment, whereas it significantly increased in the PL group. The results suggest that acute PXN ingestion (200 mg) may affect some measures of short-term memory, reasoning, and response time to cognitive challenges and help sustain attention.

Caffeine as a Factor Influencing the Functioning of the Human Body-Friend or Foe?

Nowadays, caffeine is one of the most commonly consumed substances, which presents in many plants and products. It has both positive and negative effects on the human body, and its activity concerns a variety of systems including the central nervous system, immune system, digestive system, respiratory system, urinary tract, etc. These effects are dependent on quantity, the type of product in which caffeine is contained, and also on the individual differences among people (sex, age, diet etc.). The main aim of this review was to collect, present, and analyze the available information including the latest discoveries on the impact of caffeine on human health and the functioning of human body systems, taking into account the role of caffeine in individual disease entities. We present both the positive and negative sides of caffeine consumption and the healing properties of this purine alkaloid in diseases such as asthma, Parkinson's disease, and others, not forgetting about the negative effects of excess caffeine (e.g., in people with hypertension, children, adolescents, and the elderly). In summary, we can conclude, however, that caffeine has a multi-directional influence on various organs of the human body, and because of its anti-oxidative properties, it was, and still is, an interesting topic for research studies including those aimed at developing new therapeutic strategies.

Is Coffee a Useful Source of Caffeine Preexercise?

Caffeine is a well-established ergogenic aid, with its performance-enhancing effects demonstrated across a wide variety of exercise modalities. Athletes tend to frequently consume caffeine as a performance enhancement method in training and competition. There are a number of methods available as a means of consuming caffeine around exercise, including caffeine anhydrous, sports drinks, caffeine carbohydrate gels, and gum. One popular method of caffeine ingestion in nonathletes is coffee, with some evidence suggesting it is also utilized by athletes. In this article, we discuss the research pertaining to the use of coffee as an ergogenic aid, exploring (a) whether caffeinated coffee is ergogenic, (b) whether dose-matched caffeinated coffee provides a performance benefit similar in magnitude to caffeine anhydrous, and (c) whether decaffeinated coffee consumption affects the ergogenic effects of a subsequent isolated caffeine dose. There is limited evidence that caffeinated coffee has the potential to offer ergogenic effects similar in magnitude to caffeine anhydrous; however, this requires further investigation. Coingestion of caffeine with decaffeinated coffee does not seem to limit the ergogenic effects of caffeine. Although caffeinated coffee is potentially ergogenic, its use as a preexercise caffeine ingestion method represents some practical hurdles to athletes, including the consumption of large volumes of liquid and difficulties in quantifying the exact caffeine dose, as differences in coffee type and brewing method may alter caffeine content. The use of caffeinated coffee around exercise has the potential to enhance performance, but athletes and coaches should be mindful of the practical limitations.

Caffeine metabolites are associated with different forms of caffeine supplementation and with perceived exertion during endurance exercise

This investigation compared the urine caffeine metabolites produced from different forms of caffeine supplementation given to runners 15 minutes before a series of 5-km running trials. Fourteen amateur competitive runners completed a series of self-paced outdoor time trials following ingestion of placebo or one of three alternate forms of caffeine supplement. Trials were randomized in a crossover design with equivalent doses of caffeine (4.0 mg.kg-1) administered 15 minutes before each trial via chewing gum, a novel dissolvable mouth strip or tablet. Runners produced a urine sample following each caffeinated trial that was tested for caffeine and its metabolites by high-performance liquid chromatography. The tablet form of caffeine produced a lower (p = 0.04) urinary ratio of the metabolite paraxanthine to caffeine compared with either gum or strip. Independently of caffeine delivery mode, subjects who metabolized a higher proportion of caffeine to paraxanthine recorded a lower (p = 0.01) perceived exertion. We demonstrate that oral swallowed caffeine administered 15 minutes before 5-km running is less metabolized compared with caffeinated products designed to be chewed or dissolved in the mouth. We suggest the metabolism of caffeine to paraxanthine has an inverse relationship with perceived exertion independently of caffeine delivery mode.

Acute caffeine intake in humans reduces post exercise performance in learning and memory

OBJECTIVE

To clarify the acute effect of caffeine on postexercise memory and learning performance.

METHODS

Eight male slow-to-normal caffeine metabolizers, unhabituated to caffeine, were recruited into this randomized, double blind, placebo controlled, cross over study. Caffeine (150 mg) or the placebo was consumed one hour prior to two 30 min submaximal cycling sessions. Blood was collected at the beginning, after 20 and 35 min of exercise and 30 min postexercise. Mature brain-derived neurotrophic factor (BDNF) and proBDNF concentrations were determined. Auditory memory was assessed immediately, 30 min and 24 h postexercise.

RESULTS

Participants averaged lower scores in every measure of learning and memory after ingesting caffeine compared to the placebo. Although the mean did not differ significantly for all measures, significant differences were found between the caffeine and placebo groups for the three indices; learning over time, short-term index and retroactive interference. The ratio of serum mBDNF:proBDNF increased with exercise across all time points. No significant difference in the mBDNF:proBDNF ratio was observed between treatment groups.

CONCLUSION

The consumption of caffeine prior to exercise may impair an unhabituated individual's capacity to learn and recall auditory information postexercise. However it is yet to be elucidated whether this is through caffeine's modulating effects on brain BDNF.

Quantitative In Vitro-to-In Vivo Extrapolation: Nominal versus Freely Dissolved Concentration

Discussions are ongoing on which dose metric should be used for quantitative in vitro-to-in vivo extrapolation (QIVIVE) of in vitro bioassay data. The nominal concentration of the test chemicals is most commonly used and easily accessible, while the concentration freely dissolved in the assay medium is considered to better reflect the bioavailable concentration but is tedious to measure. The aim of this study was to elucidate how much QIVIVE results will differ when using either nominal or freely dissolved concentrations. QIVIVE_nom and QIVIVE_free ratios, that is, the ratios of plasma concentrations divided by in vitro effect concentrations, were calculated for 10 pharmaceuticals using previously published nominal and freely dissolved effect concentrations for the activation of the peroxisome proliferator-activated receptor gamma (PPARγ) and the activation of oxidative stress response. The QIVIVE_nom ratios were higher than QIVIVE_free ratios by up to a factor of 60. The risk of in vivo effects was classified as being high or low for four chemicals using the QIVIVE_nom and for three chemicals using QIVIVE_free ratios. Unambiguous classification was possible for nine chemicals by combining the QIVIVE_nom or QIVIVE_free ratios with the respective specificity ratios (SR_nom or SR_free) of the in vitro effect data, which helps to identify whether the specific effect was influenced by cytotoxicity. QIVIVE_free models should be preferred as they account for differences in bioavailability between in vitro and in vivo, but QIVIVE_nom may still be useful for screening the effects of large numbers of chemicals because it is generally more conservative. The use of SR of the in vitro effect data as a second classification factor is recommended for QIVIVE_nom and QIVIVE_free models because a clearer picture can be obtained with respect to the likelihood that a biological effect will occur and that it is not caused by nonspecific cytotoxicity.

Massive suicidal ingestion of caffeine: a case report with investigation of the cardiovascular effect/concentration relationships

BACKGROUND

Caffeine poisoning may cause life-threatening arrhythmias and hemodynamic failure. We aimed to investigate the toxicokinetics (TK), toxicodynamics (TD) and TK/TD relationships of caffeine in a case of poisoning.

CASE REPORT

A 47-year-old male ingested pure anhydrous caffeine powder (70 g) in a suicide attempt. He developed agitation, tachycardia, and two episodes of ventricular fibrillation treated with defibrillation and tracheal intubation. He was successfully managed using intravenous infusions of esmolol and norepinephrine.

METHODS

We modelled the time-course of plasma caffeine concentration (TK study using online liquid chromatography-tandem mass spectrometry), the time-course of blood lactate concentration and infusion rates of esmolol and norepinephrine (TD studies) and the TK/TD relationships.

RESULTS

Caffeine TK was of first-order peaking at 258 mg/L with an elimination half-life of 46.2 h and clearance of 2.2 L/h. Caffeine-related effects on blood lactate (peak, 10 mmol/L at 1.25 h postingestion) were described by a Bateman-type equation (formation rate, 0.05 mmol/mg.h; elimination rate, 0.9 mmol/mg.h). Esmolol and norepinephrine infusion rates to reverse caffeine-related cardiovascular effects (peaks at 51-h postingestion) fitted well with a sigmoidal E_max model (EC₅₀, 180.0 and 225.9 mg/L, respectively; Hill coefficient, 10.0).

CONCLUSION

Massive caffeine ingestion is characterized by prolonged caffeine elimination. TK/TD relationships are helpful to quantify caffeine-related catecholaminergic effects.

Interactions between reinforcement history and drug-primed reinstatement: Studies with MDPV and mixtures of MDPV and caffeine

Many drugs of abuse are mixed with other psychoactive substances (e.g., caffeine) prior to their sale or use. Synthetic cathinones (e.g., 3,4-methylenedioxypyrovalerone [MDPV]) are commonly mixed with caffeine or other cathinones (e.g., 3,4-methylenedioxy-N-methylcathinone [methylone]), and these "bath salts" mixtures (e.g., MDPV + caffeine) can exhibit supra-additive interactions with regard to their reinforcing and discriminative stimulus properties. However, little is known about relapse-related effects of drug mixtures. In these studies, male Sprague-Dawley rats self-administered 0.032 mg/kg/inf MDPV or a mixture of MDPV + caffeine (0.029 + 0.66 mg/kg/inf, respectively) and then underwent multiple rounds of extinction and reinstatement testing to evaluate the influence of reinforcement history and drug-associated stimuli on the effectiveness of saline (drug-paired stimuli alone), MDPV (0.032-1.0 mg/kg), caffeine (1.0-32 mg/kg), and mixtures of MDPV:caffeine (in 3:1, 1:1, and 1:3 ratios, relative to each drug's ED₅₀ ) to reinstate responding. Dose-addition analyses were used to determine the nature of the drug-drug interaction for each mixture. MDPV and caffeine dose-dependently reinstated responding and were equally effective, regardless of reinforcement history. Most fixed ratio mixtures of MDPV + caffeine exhibited supra-additive interactions, reinstating responding to levels greater than was observed with caffeine and/or MDPV alone. Drug-associated stimuli also played a key role in reinstating responding, especially for caffeine. Together, these results demonstrate that the composition of drug mixtures can impact relapse-related effects of drug mixtures, and "bath salts" mixtures (MDPV + caffeine) may be more effective at promoting relapse-related behaviors than the constituents alone. Further research is needed to determine how other polysubstance reinforcement histories can impact relapse-related behaviors.

Potential implications of DMET ontogeny on the disposition of commonly prescribed drugs in neonatal and pediatric intensive care units

Introduction: Pediatric patients, especially neonates and infants, are more susceptible to adverse drug events as compared to adults. In particular, immature small molecule drug metabolism and excretion can result in higher incidences of pediatric toxicity than adults if the pediatric dose is not adjusted.Area covered: We reviewed the top 29 small molecule drugs prescribed in neonatal and pediatric intensive care units and compiled the mechanisms of their metabolism and excretion. The ontogeny of Phase I and II drug metabolizing enzymes and transporters (DMETs), particularly relevant to these drugs, are summarized. The potential effects of DMET ontogeny on the metabolism and excretion of the top pediatric drugs were predicted. The current regulatory requirements and recommendations regarding safe and effective use of drugs in children are discussed. A few representative examples of the use of ontogeny-informed physiologically based pharmacokinetic (PBPK) models are highlighted.Expert opinion: Empirical prediction of pediatric drug dosing based on body weight or body-surface area from the adult parameters can be inaccurate because DMETs are not mature in children and the age-dependent maturation of these proteins is different. Ontogeny-informed-PBPK modeling provides a better alternative to predict the pharmacokinetics of drugs in children.

Severe Caffeine Intoxication Treated With Hemodialysis: A Case Report

Caffeine is well known for its central nervous system–stimulating effect. Toxicity may occur following high-dose caffeine ingestions. We describe a case of caffeine intoxication secondary to reported ingestion of a large dose of caffeine (60,000 mg in tablet form) with an initial serum caffeine level of 608 μmol/L (known lethal serum level starting from 412 μmol/L). This case demonstrates the key clinical manifestations of caffeine intoxication and the effect of its associated massive adrenergic surge with neurologic symptoms, cardiovascular instability, metabolic abnormalities, and the significant risk of mortality. We highlight important kidney management considerations, including protective measures against electrolyte disturbances such as hypokalemia and hypophosphatemia, and the use of prolonged hemodialysis for caffeine elimination. We share our practical decision making and approach to dialysis discontinuation if serum caffeine level reporting is unavailable or delayed.

Massive β1-Adrenergic Receptor Reaction Explains Irreversible Acute Arrhythmia in a Fatal Case of Acute Pure Caffeine Intoxication

Caffeine, a naturally occurring purine-based alkaloid, is the most consumed psychostimulant worldwide. Since caffeine pharmacokinetics shows extreme interindividual variability, it is not easy to establish its toxic dose. Only a few cases of death due to acute caffeine intoxication have been described so far, the majority of which attributable to massive assumption of caffeine-based medications. We present a case of acute caffeine overdose due to ingestion of pure caffeine. The extremely high blood concentration of caffeine determined a strong cardiovascular response, leading to fatal arrhythmia, as supported by histological evidence of myocardial injury. Quantitation of catecholamines and their metabolites in urine samples was performed and showed level near the highest limit of normal ranges for norepinephrine and high level of epinephrine. Contraction band is a pathological modification of the myocell caused by the catecholaminergic action and can occur in conditions of alteration due to the interaction between calcium and catecholamines. We demonstrated the β1-adrenoceptor involvement in our fatal case by immunohistochemical analysis.

Pharmacokinetics, pharmacodynamics and metabolism of caffeine in newborns

The plasma elimination half-life of caffeine in the newborn is approximately 100 h. Caffeine is rapidly absorbed with complete bioavailability following oral dosing. Switching between parenteral and oral administration requires no dose adjustments. Caffeine has wide interindividual pharmacodynamic variability and a wide therapeutic index in preterm newborns. Thresholds of measurable efficacy on respiratory drive have been documented at plasma levels around 2 mg/L. At these low levels, caffeine competitively inhibits adenosine receptors (A1 and A2A). The toxicity threshold is ill-defined and possibly as high as 60 mg/L which can be lethal in adults. High doses of caffeine may produce better control of apnea. However, at high systemic drug concentrations, the pharmacodynamic actions of caffeine become more complex and worrisome. They include inhibition of GABA receptors and cholinergic receptors in addition to adenosine receptor inhibition, intracellular calcium mobilization and actions on adrenergic, dopaminergic and phosphodiesterase systems. The role of pharmacogenomic factors as determinants of neonatal pharmacologic response and clinical effects remains to be explored.

The Influence of Recreational Substance Use in TMS Research

(1) Background: Transcranial magnetic stimulation (TMS) approaches are widely used to study cortical and corticospinal function. However, responses to TMS are subject to significant intra-and inter-individual variability. Acute and chronic exposure to recreational substances alters the excitability of the sensorimotor system and may contribute to the variability in TMS outcome measures. The increasing prevalence of recreational substance use poses a significant challenge for executing TMS studies, but there is a lack of clarity regarding the influence of these substances on sensorimotor function. (2) Methods: The literature investigating the influence of alcohol, nicotine, caffeine and cannabis on TMS outcome measures of corticospinal, intracortical and interhemispheric excitability was reviewed. (3) Results: Both acute and chronic use of recreational substances modulates TMS measures of excitability. Despite the abundance of research in this field, we identify knowledge gaps that should be addressed in future studies to better understand the influence of these substances on TMS outcomes. (4) Conclusions: This review highlights the need for TMS studies to take into consideration the history of participant substance use and to control for acute substance use prior to testing.

Functional and cognitive responses to caffeine intake in middle-aged women are dose depending

Middle-aged women display many physiological and cognitive alterations resulting from aging and physical inactivity as well as other changes that occur as a function of menopause. Caffeine consumption is highest in this age with women having a particular greater sensitivity to caffeine than men. Its effects on functional and cognitive functions are controversial and seem to depend on the dose intake. This study aimed to assess the effect of low (100mg) and high (400mg) doses of caffeine consumption on cognitive (simple reaction time) and functional (upper and low body muscle endurance, aerobic endurance and functional mobility) performances. These performances were evaluated in 19 healthy middle-aged women by the 30-Second Chair Stand test for lower body muscle endurance, the 30sec Arm Curl Test for upper body muscle endurance, the 2-Minute Step test for aerobic endurance, The Timed Up and Go test for functional mobility and the simple reaction time test for reaction time, 60min after a treatment capsule intake (100mg caffeine/400mg caffeine/placebo). Low caffeine consumption significantly improved (p<.005) cognitive performance, while high caffeine consumption did not. However, the functional performance significantly improved (p<.05) after high caffeine consumption but not after low caffeine consumption. Except, the functional mobility performance significantly improved (p<.05) after both low and high caffeine consumption with better improvement (p<.05) after the high dose. In conclusion, low caffeine consumption improved cognitive performance and high caffeine consumption improved functional performance but the functional mobility improved after both low and high caffeine consumption in middleaged women.

Effects of Chronic Caffeine Administration on Behavioral and Molecular Adaptations to Sensory Contact Model Induced Stress in Adolescent Male Mice

Previous studies have shown that caffeine attenuates stress-induced mood dysfunction and memory deterioration through neuronal adenosine A2A receptors antagonism. However, whether caffeine exerts this effect through modulating other molecular targets, which interfere with the resilience to social defeat stress in adolescent male mice is unknown. This study was conducted to investigate the role of caffeine in the behavioral responses to social stress induced by the sensory contact model (SCM) and the possible alteration of the gene expression level of Na/K ATPase pump. Adolescent male mice were exposed to SCM for 12 days. Caffeine was administered intraperitoneal daily for 14 days after SCM. The time spent in interaction zone, social interaction ratio, preference index to novel objects, time spent in the open arms and immobility time in forced swimming test were used to measure the locomotor activity, social avoidance, short-term memory, anxiety and depression in mice. The results showed that chronic treatment with caffeine for 14 days improved locomotor activity, reversed the avoidance of social behavior, improved preference to novel objects, and reversed depression induced by social defeat stress in adolescent male mice, suggesting the enhancement of the resilience to social defeat stress induced by caffeine. Moreover, caffeine treatment did alter gene expression levels of Na/K ATPase isoforms in both prefrontal cortex and hippocampus. Altered gene expression was significant in most cases and correlates with the observed behavioral changes. Taken together, our findings provide new insight into the effects of chronic caffeine administration on locomotor activity, social avoidance, short-term memory and depression in adolescent male mice exposed to SCM.

Can caffeine intake combined with aerobic exercise lead to improvement in attentional and psychomotor performance in trained individuals?

•

Supplementation effect was found, suggesting distinct interaction mechanisms between attention and SRT (simple reaction time).

•

The change in the SRT magnitude increased after 60 min from caffeine intake, and even more after exercise.

•

The decrease in the SRT magnitude after caffeine intake and exercise suggests additional effects of caffeine on exercise.

To evaluate the acute effects of ingestion of 500 mg of caffeine in addition to aerobic exercise on the optimization of cognitive attention tasks and simple reaction time. Twenty men were randomly divided into two groups, caffeine (CAF) and placebo (PLA), and underwent cardiopulmonary exercise testing and cognitive testing (D2SLK, D2GZ, D2F% and TRS). Then, both ingested 500 mg of caffeine or placebo (double blind), and after 60 min performed a 30-minute continuous exercise session at 70 % VO2Max. Cognitive tests were repeated immediately after exercise, and after 30 min. D2SLK, D2GZ, D2F% and TRS scores were compared by repeated measures ANOVA. The magnitude of the effect was established, and it was considered meaningful p = 0.05. CAF is able to alter D2SLK and also reduce D2F% (0.001 - moderate effect, 0.82) and improve the task after 30 min of exercise (p = 0.014 - moderate effect 0.95). The TRS showed significant gains for the CAF group compared to PLA (0.000 - high effect 1.76). Caffeine induces significant effects in attention and reaction time domains independent of the effect of aerobic exercise.

Caffeine inhalation effects on locomotor activity in mice

It is estimated that 80% of the world's population consumes caffeine from beverages and food every day. The traditional form of caffeine intake is oral, but more recently people have been inhaling caffeine using nasal sprays. However, the effects of caffeine inhalation are not well understood. The purpose of this study was to determine whether caffeine inhalation affects mouse behavior. To test this, we compared spontaneous activity of mice following inhalation and intraperitoneal administration of caffeine. Next, we investigated whether spontaneous activity changed with the time and/or concentration of caffeine inhaled. We found that mice that inhaled caffeine increased their spontaneous activity similar to mice that were administered caffeine intraperitoneally. Furthermore, spontaneous activity increased in an inhalation time-dependent and concentration-dependent manner. These results show that caffeine-induced stimulation also occurs by inhalation in mice, which suggests that caffeine can reach the brain even by inhalation. This study is useful not only for creating new administration methods of caffeine but also for adjusting caffeine storage and management.

The Psychobiological Etiology of Gastrointestinal Distress in Sport: A Review

Gastrointestinal (GI) disturbances are common during training and competition, especially among endurance athletes. Historically, little attention has been paid to the psychobiological etiology of GI problems in sport. The aim of this review is to: (1) provide a physiological overview of how psychological stress and anxiety impact GI system function; (2) review the literature that has examined the role of stress and anxiety in GI distress in athletes; and (3) provide suggestions for future research. Animal and human studies have documented that psychological stressors reduce gastric motility and delay stomach emptying while simultaneously increasing large intestine motility. These functional changes are likely mediated through the secretion of corticotropin-releasing factor and subsequent alterations in autonomic nervous system activity, which act to reduce splanchnic blood flow and increase GI permeability. In addition, chronic stress and anxiety may worsen GI discomfort by increasing visceral hypersensitization. Still, only a couple of studies have found modest associations between stress, anxiety, and the occurrence/severity of GI distress in active populations. As such, future work should attempt to confirm that experimentally inducing psychological stress results in the aforementioned GI problems during exercise. Furthermore, studies are needed to determine how psychological stress impacts the tolerance to nutritional fueling and whether it worsens the GI permeability that normally occurs with exercise.

Caffeine Uptake into the Vitreous after Peroral Coffee Consumption

INTRODUCTION

Caffeine and its metabolites have antioxidant activity, scavenging reactive oxygen species. The aim of our study was to measure caffeine concentrations in vitreous samples after peroral caffeine intake.

METHODS

This prospective study included patients scheduled for 23-G pars plana vitrectomy with membrane peeling due to epiretinal membranes. The study was performed in two parts: in the first part, patients were recruited into three different groups: group A consisted of habitual coffee drinkers who agreed to drink coffee containing 180 mg caffeine 1 h before surgery (n = 10), group B consisted of habitual coffee drinkers who were not offered coffee before surgery (n = 5), and group C consisted of non-habitual coffee drinkers, forming the control group (n = 5). In the second part (group D) patients (habitual coffee drinkers) agreed to give additional blood serum samples for measurement of caffeine concentration. Harvested samples of vitreous (groups A-D), epiretinal membranes (groups A-C), and blood serum samples (group D) were examined for concentrations of caffeine with gas chromatography-mass spectrometry.

RESULTS

Samples of 40 eyes of 40 patients were harvested. The concentrations of caffeine in the vitreous samples were 1,998 ± 967 ng/mL in group A and 1,108 ± 874 ng/mL in group B. In group C, caffeine concentrations were below 176 ng/mL in all vitreous samples. Both groups A and B had significantly higher concentrations of caffeine in the vitreous samples than group C (p < 0.002, p < 0.01, Mann-Whitney U test). Caffeine concentrations in epiretinal membranes were below the limits of detection. Correlation of caffeine concentrations between blood serum samples and vitreous samples in group D was high, with significantly higher caffeine concentrations in the blood serum.

CONCLUSION

Coffee consumption leads to significant caffeine levels in the vitreous compared to patients in the control group, and caffeine concentrations in the vitreous showed a high correlation to blood serum concentrations of caffeine after peroral coffee consumption.

Absorption spectra of xanthines in aqueous solution: a computational study

We present a detailed computational analysis of the UV/Vis spectra of caffeine, paraxanthine and theophylline in aqueous solution. A hierarchy of solvation approaches for modeling the aqueous environment have been tested, ranging from the continuum model to the non-polarizable and polarizable quantum mechanical (QM)/molecular mechanics (MM) models, with and without the explicit inclusion of water molecules in the QM portion. The computed results are directly compared with the experimental data, thus highlighting the role of electrostatic, polarization and hydrogen boding solute-solvent interactions.

Effects of Caffeine and Acute Aerobic Exercise on Working Memory and Caffeine Withdrawal

Studies show that a single bout of exercise confers cognitive benefits. However, many individuals use psychoactive substances such as caffeine to enhance cognitive performance. The effects of acute exercise in comparison to caffeine on cognition remain unknown. Furthermore, caffeine use is associated with withdrawal symptoms upon cessation. Whether acute exercise can reduce withdrawal symptoms also remains unknown. The objectives of this study were to compare the effects of acute moderate intensity aerobic exercise to caffeine on working memory (WM) and caffeine withdrawal symptoms (CWS). In Phase I, non-caffeine (n = 29) and caffeine consumers (n = 30) completed a WM assessment, followed by acute exercise and caffeine. In Phase II, caffeine consumers (n = 25) from Phase I underwent the WM assessment and reported CWS following a 12-hour deprivation period. Acute moderate intensity aerobic exercise and caffeine (1.2 mg/kg) significantly improved WM accuracy and reduced CWS comparably. WM performance was not reduced following caffeine deprivation.

Oxidative Stress Mediates Anxiety-Like Behavior Induced by High Caffeine Intake in Zebrafish: Protective Effect of Alpha-Tocopherol

Anxiety is a common symptom associated with high caffeine intake. Although the neurochemical mechanisms of caffeine-induced anxiety remain unclear, there are some evidences suggesting participation of oxidative stress. Based on these evidences, the current study is aimed at evaluating the possible protective effect of alpha-tocopherol (TPH) against anxiety-like behavior induced by caffeine (CAF) in zebrafish. Adult animals were treated with CAF (100 mg/kg) or TPH (1 mg/kg)+CAF before behavioral and biochemical evaluations. Oxidative stress in the zebrafish brain was evaluated by a lipid peroxidation assay, and anxiety-like behavior was monitored using light/dark preference and novel tank diving test. Caffeine treatment evoked significant elevation of brain MDA levels in the zebrafish brain, and TPH treatment prevented this increase. Caffeine treatment also induced anxiety-like behavior, while this effect was not observed in the TPH+CAF group. Taken together, the current study suggests that TPH treatment is able to inhibit oxidative stress and anxiety-like behavior evoked by caffeine.

Fast analysis of caffeinated beverages using laser diode thermal desorption mass spectrometry (LDTD-MS/MS)

A rapid method for quantitative caffeine analysis in carbonated and non-carbonated beverages and liquid dietary supplement products was developed based on the direct sample introduction technique of laser diode thermal desorption atmospheric pressure chemical ionisation with tandem mass spectrometry (LDTD-MS/MS). Product samples were diluted with a mixture of methanol, water, and d₃-caffeine internal standard. Sample aliquots were filtered, spotted on a metal-lined LDTD microtitre plate, dried, and thermally desorbed for subsequent ionisation and analysis by MS/MS analysis. Each sample required a 6 s desorption, and sample-to-sample analysis time of less than 30 s per sample. Caffeine yielded a linear calibration curve over the range 0.5-100 μg mL^-1 (R² > 0.995). Caffeine recoveries from fortified samples ranged from 97% to 107% with <5% RSD. The caffeine determination was not affected by matrix interferences despite the large range of ingredients, vitamins, sweeteners, extracts, and additives present in the products tested, even though LDTD-MS/MS is a whole-sample desorption technique with no separation of matrix background. The method detection limit was below 0.12 μg mL^-1. The method was applied to 33 caffeinated products and LDTD-MS/MS quantitative results closely correlated (R² > 0.998) with the regulatory standard HPLC-UV method (AOAC Official Method 979.08).

A Physiologically Based Pharmacokinetic Model for Pregnant Women to Predict the Pharmacokinetics of Drugs Metabolized Via Several Enzymatic Pathways

BACKGROUND

Physiologically based pharmacokinetic modeling is considered a valuable tool for predicting pharmacokinetic changes in pregnancy to subsequently guide in-vivo pharmacokinetic trials in pregnant women. The objective of this study was to extend and verify a previously developed physiologically based pharmacokinetic model for pregnant women for the prediction of pharmacokinetics of drugs metabolized via several cytochrome P450 enzymes.

METHODS

Quantitative information on gestation-specific changes in enzyme activity available in the literature was incorporated in a pregnancy physiologically based pharmacokinetic model and the pharmacokinetics of eight drugs metabolized via one or multiple cytochrome P450 enzymes was predicted. The tested drugs were caffeine, midazolam, nifedipine, metoprolol, ondansetron, granisetron, diazepam, and metronidazole. Pharmacokinetic predictions were evaluated by comparison with in-vivo pharmacokinetic data obtained from the literature.

RESULTS

The pregnancy physiologically based pharmacokinetic model successfully predicted the pharmacokinetics of all tested drugs. The observed pregnancy-induced pharmacokinetic changes were qualitatively and quantitatively reasonably well predicted for all drugs. Ninety-seven percent of the mean plasma concentrations predicted in pregnant women fell within a twofold error range and 63% within a 1.25-fold error range. For all drugs, the predicted area under the concentration-time curve was within a 1.25-fold error range.

CONCLUSION

The presented pregnancy physiologically based pharmacokinetic model can quantitatively predict the pharmacokinetics of drugs that are metabolized via one or multiple cytochrome P450 enzymes by integrating prior knowledge of the pregnancy-related effect on these enzymes. This pregnancy physiologically based pharmacokinetic model may thus be used to identify potential exposure changes in pregnant women a priori and to eventually support informed decision making when clinical trials are designed in this special population.

Zolpidem and Gender: Are Women Really At Risk?

BACKGROUND

In 2013 the Food and Drug Administration (FDA) claimed the existence of new data showing women to be at risk for excessive daytime sedation and impaired driving proficiency following bedtime doses of zolpidem. The putative explanation was the reduced metabolic clearance of zolpidem and higher morning blood concentrations in women compared to men. The FDA acted to reduce the recommended dosage for women down to 50% of the dose for men. No other regulatory agency worldwide has taken similar action.

METHODS

Gender effects on zolpidem pharmacokinetics, pharmacodynamics, adverse effects, clinical efficacy, and driving performance were evaluated through a further analysis of data from a previous study, together with a literature review.

RESULTS

Women had on average 35% lower apparent clearance of zolpidem than men (236 vs 364 mL/min, P < 0.001). This difference was not explained by body weight. In some laboratory studies, women had greater functional impairment than men taking the same dose, but in all studies active drug was not distinguishable from placebo at 8 hours after oral dosage. On-the-road driving studies likewise showed no evidence of driving impairment in men or women at 8 hours after 10 mg of oral immediate-release zolpidem. No clinical trial demonstrated a gender-related difference in clinical efficacy or adverse reactions, and there was no evidence of a particular risk to women.

CONCLUSIONS

Dosage reduction in women is not supported by available scientific evidence, and may in fact lead to underdosing and the consequent hazard of inadequately treated insomnia.

'I think I'm gonna hurl': A Narrative Review of the Causes of Nausea and Vomiting in Sport

Exercise-associated gastrointestinal (GI) distress can negatively impact athletic performance and interfere with exercise training. Although there are a few universal underlying causes of GI distress, each symptom often has its own unique triggers and, therefore, its own prevention and management strategies. One of the most troubling GI symptoms an athlete can experience during training and competition is nausea/vomiting. The prevalence of nausea varies with several factors, two of the most important being exercise intensity and duration. Relatively brief, high-intensity exercise (e.g., sprinting, tempo runs) and ultra-endurance exercise are both associated with more frequent and severe nausea. The potential causes of nausea in sport are numerous and can include catecholamine secretion, hypohydration, heat stress, hyponatremia, altitude exposure, excessive fluid/food consumption, hypertonic beverage intake, pre-exercise intake of fatty- or protein-rich foods (especially in close proximity to exercise), prolonged fasting, various supplements (caffeine, sodium bicarbonate, ketones), certain drugs (antibiotics, opioids), GI infections, and competition-related anxiety. Beyond directly addressing these aforementioned causes, antiemetic drugs (e.g., ondansetron) may also be useful for alleviating nausea in some competitive situations. Given the commonness of nausea in sport and its potential impact on exercise performance, athletes and sports medicine practitioners should be aware of the origins of nausea and strategies for dealing with this troublesome gut complaint.

Caffeine Consumption through Coffee: Content in the Beverage, Metabolism, Health Benefits and Risks

Caffeine (1,3,7-trimethylxanthine) is the most consumed psychoactive substance in the world, acting by means of antagonism to adenosine receptors, mainly A1 and A2A. Coffee is the main natural source of the alkaloid which is quite soluble and well extracted during the brew’s preparation. After consumption, caffeine is almost completely absorbed and extensively metabolized in the liver by phase I (cytochrome P450) enzymes, mainly CYP1A2, which appears to be polymorphically distributed in human populations. Paraxanthine is the major caffeine metabolite in plasma, while methylated xanthines and methyluric acids are the main metabolites excreted in urine. In addition to stimulating the central nervous system, caffeine exerts positive effects in the body, often in association with other substances, contributing to prevention of several chronic diseases. The potential adverse effects of caffeine have also been extensively studied in animal species and in humans. These aspects will be approached in the present review.

Effects of strategic early-morning caffeine gum administration on association between salivary alpha-amylase and neurobehavioural performance during 50 h of sleep deprivation

Self-assessment is the most common method for monitoring performance and safety in the workplace. However, discrepancies between subjective and objective measures have increased interest in physiological assessment of performance. In a double-blind placebo-controlled study, 23 healthy adults were randomly assigned to either a placebo (n = 11; 5 F, 6 M) or caffeine condition (n = 12; 4 F, 8 M) while undergoing 50 h (i.e. two days) of total sleep deprivation. In previous work, higher salivary alpha-amylase (sAA) levels were associated with improved psychomotor vigilance and simulated driving performance in the placebo condition. In this follow-up article, the effects of strategic caffeine administration on the previously reported diurnal profiles of sAA and performance, and the association between sAA and neurobehavioural performance were investigated. Participants were given a 10 h baseline sleep opportunity (monitored via standard polysomnography techniques) prior to undergoing sleep deprivation (total sleep time: placebo = 8.83 ± 0.48 h; caffeine = 9.01 ± 0.48 h). During sleep deprivation, caffeine gum (200 mg) was administered at 01:00 h, 03:00 h, 05:00 h, and 07:00 h to participants in the caffeine condition (n = 12). This strategic administration of caffeine gum (200 mg) has been shown to be effective at maintaining cognitive performance during extended wakefulness. Saliva samples were collected, and psychomotor vigilance and simulated driving performance assessed at three-hour intervals throughout wakefulness. Caffeine effects on diurnal variability were compared with previously reported findings in the placebo condition (n = 11). The impact of caffeine on the circadian profile of sAA coincided with changes in neurobehavioural performance. Higher sAA levels were associated with improved performance on the psychomotor vigilance test during the first 24 h of wakefulness in the caffeine condition. However, only the association between sAA and response speed (i.e. reciprocal-transform of mean reaction time) was consistent across both days of sleep deprivation. The association between sAA and driving performance was not consistent across both days of sleep deprivation. Results show that the relationship between sAA and reciprocal-transform of mean reaction time on the psychomotor vigilance test persisted in the presence of caffeine, however the association was relatively weaker as compared with the placebo condition.

Does Improved Attention Induced by Caffeine Intake Affect Olfactory Function?

Objectives

Past several studies have proven that caffeine facilitates attentional enhancement by acting as an adenosine antagonist once it is absorbed by the body, resulting in improved psycho-behavioral function. Modern clinical olfactory function tests are usually assessed by psychophysical tests but due to a paucity of data, the influence of enhanced attention by caffeine on olfactory function still remains unclear. The objective of this study was to compare results of cognitive function (attention) and olfactory function before and after caffeine administration in order to analyze effects of caffeine on olfactory function in normosmic subjects.

Methods

This study enrolled 49 participants of Konkuk University Hospital with a mean age of 27.7 years who had patent olfactory clefts and no olfactory dysfunction from May 2015 to February 2016. Subjects were restrained from caffeine 10 hours before the test. On day 1, participant’s subjective olfactory function was evaluated before and after uptake of either caffeinated or decaffeinated coffee using visual analog scale (VAS) score, minimum cross-sectional area (MCA) measured by acoustic rhinometry, and the Korean version of Sniffin’ Stick II (KVSS II). Evaluation of participant’s attentional degree was measured by d2 test. On day 2, the same procedure was carried out with counterpart substance. The type of coffee initially administrated was randomly selected.

Results

After administration, caffeinated coffee resulted in significant attentional enhancement than decaffeinated coffee. Results of d2 test showed statistically significant differences in the parameters of total number of errors and omission errors. In both the caffeinated and decaffeinated groups, the patients showed slight increase in VAS score and nasal cavity area; however, the difference was not statistically significant. Also, caffeinated coffee intake compared to decaffeinated coffee intake showed no significant relevance to olfactory function.

Conclusion

Caffeine may significantly improve attentional congnitive function, while not have acute effects on olfactory function.

Administration of Caffeine in Alternate Forms

There has been recent interest in the ergogenic effects of caffeine delivered in low doses (~ 200 mg or ~ 3 mg/kg body mass) and administered in forms other than capsules, coffee and sports drinks, including chewing gum, bars, gels, mouth rinses, energy drinks and aerosols. Caffeinated chewing gum is absorbed quicker through the buccal mucosa compared with capsule delivery and absorption in the gut, although total caffeine absorption over time is not different. Rapid absorption may be important in many sporting situations. Caffeinated chewing gum improved endurance cycling performance, and there is limited evidence that repeated sprint cycling and power production may also be improved. Mouth rinsing with caffeine may stimulate nerves with direct links to the brain, in addition to caffeine absorption in the mouth. However, caffeine mouth rinsing has not been shown to have significant effects on cognitive performance. Delivering caffeine with mouth rinsing improved short-duration, high-intensity, repeated sprinting in normal and depleted glycogen states, while the majority of the literature indicates no ergogenic effect on aerobic exercise performance, and resistance exercise has not been adequately studied. Studies with caffeinated energy drinks have generally not examined the individual effects of caffeine on performance, making conclusions about this form of caffeine delivery impossible. Caffeinated aerosol mouth and nasal sprays may stimulate nerves with direct brain connections and enter the blood via mucosal and pulmonary absorption, although little support exists for caffeine delivered in this manner. Overall, more research is needed examining alternate forms of caffeine delivery including direct measures of brain activation and entry of caffeine into the blood, as well as more studies examining trained athletes and female subjects.

The clinical toxicology of caffeine: A review and case study

Caffeine is a widely recognized psychostimulant compound with a long history of consumption by humans. While it has received a significant amount of attention there is still much to be learned with respect to its toxicology in humans, especially in cases of overdose. A review of the history of consumption and the clinical toxicology of caffeine including clinical features, pharmacokinetics, toxicokinetics, a thorough examination of mechanism of action and management/treatment strategies are undertaken. While higher (i.e., several grams) quantities of caffeine are known to cause toxicity and potentially lethality, cases of mainly younger individuals who have experienced severe side effects and death despite consuming doses not otherwise known to cause such harm is troubling and deserves further study. An attempted case reconstruction is performed in an effort to shed light on this issue with a focus on the pharmacokinetics and pharmacodynamics of caffeine.

Caffeine and the eye

Caffeine, a popular psychostimulant that acts as an adenosine receptor antagonist, is the most widely used drug in history, consumed daily by people worldwide. Knowledge of the physiological and pathological effects of caffeine is crucial in improving public health because of its widespread use. We provide a summary of the current evidence on the effect of caffeine on the eye. Most of the research conducted to date is in relation to cataract and glaucoma, two of the most common eye diseases among the elderly.

Multi-ingredient pre-workout supplements, safety implications, and performance outcomes: a brief review

In recent years, a new class of dietary supplements called multi-ingredient pre-workout supplements (MIPS) has increased in popularity. These supplements are intended to be taken prior to exercise and typically contain a blend of ingredients such as caffeine, creatine, beta-alanine, amino acids, and nitric oxide agents, the combination of which may elicit a synergistic effect on acute exercise performance and subsequent training adaptations compared to single ingredients alone. Therefore, the purpose of this article was to review the theoretical rationale and available scientific evidence assessing the potential ergogenic value of acute and chronic ingestion of MIPS, to address potential safety concerns surrounding MIPS supplementation, and to highlight potential areas for future research. Though direct comparisons between formulations of MIPS or between a MIPS and a single ingredient are challenging and often impossible due to the widespread use of "proprietary blends" that do not disclose specific amounts of ingredients in a given formulation, a substantial body of evidence suggests that the acute pre-exercise consumption of MIPS may positively influence muscular endurance and subjective mood, though mixed results have been reported regarding the acute effect of MIPS on force and power production. The chronic consumption of MIPS in conjunction with a periodized resistance training program appears to augment beneficial changes in body composition through increased lean mass accretion. However, the impact of long-term MIPS supplementation on force production, muscular endurance, aerobic performance, and subjective measures is less clear. MIPS ingestion appears to be relatively safe, though most studies that have assessed the safety of MIPS are relatively short (less than eight weeks) and thus more information is needed regarding the safety of long-term supplementation. As with any dietary supplement, the use of MIPS carries implications for the athlete, as many formulations may intentionally contain banned substances as ingredients or unintentionally as contaminants. We suggest that athletes thoroughly investigate the ingredients present in a given MIPS prior to consumption. In conclusion, it appears that multi-ingredient pre-workout supplements have promise as an ergogenic aid for active individuals, though further information is required regarding long-term efficacy and safety in a wider variety of populations.

Nonlinear effects of caffeine on the viability, synthesis and gene expression of chondrocytes from the offspring of rats treated during pregnancy

OBJECTIVE

Evaluate the effects of doses of caffeine administered to pregnant rats on the articular cartilage chondrocytes of their offspring.

METHODS

Twenty-four adult Wistar rats were randomly assigned to four groups, with one control group and three groups being treated with caffeine at doses of 25, 50 and 100 mg/kg throughout pregnancy. At birth, three offspring/females were euthanized so that the chondrocytes could be extracted. At 7, 14 and 21 days of culture, the chondrocytes were subjected to the MTT cell viability assay and an evaluation of their alkaline phosphatase activity and collagen synthesis. Chondrocytes were also stained by Hematoxylin-eosin, PAS, Safranin-O and Alcian Blue. The Sox-9, Runx-2, aggrecan, collagen-II and alkaline phosphatase gene transcript levels were also evaluated. Mean comparisons were performed by the Student-Newman-Keuls test.

RESULTS

Chondrocyte cultures from the 25 mg/kg group had the lowest results, as chondrocytes from this group had reduced viability, percentage of cells, alkaline phosphatase activity and collagen and chondrogenic matrix synthesis. A reduced expression of Sox-9, alkaline phosphatase and collagen-II was also detected in the 25 mg/kg group. Chondrocyte cultures of the group treated with 50 mg/kg caffeine showed reduced collagen synthesis and Sox-9 expression. The caffeine dose of 100 mg/kg also reduced collagen and Sox-9 and alkaline phosphatase expression.

CONCLUSION

Caffeine administered to pregnant rats negatively alters the articular cartilage chondrocytes of their offspring, reducing the synthesis of collagen and Sox-9 expression regardless of the dose. This study also concluded that the effects of caffeine are not linear or dose-dependent.

A Retrospective Study on the Epidemiological and Clinical Features of Emergency Patients with Large or Massive Consumption of Caffeinated Supplements or Energy Drinks in Japan

Objective We conducted a retrospective study on the epidemiological and clinical features of patients with acute caffeine poisoning in Japan. Methods Letters requesting participation were sent to 264 emergency departments of hospitals, and questionnaires were mailed to those that agreed to participate. Patients Participants were patients transported to emergency departments of hospitals between April 2011 and March 2016 after consuming large or massive amounts of caffeinated supplements and/or energy drinks (caffeine dose ≥1.0 g). Results We surveyed 101 patients from 38 emergency departments. Since April 2013, the number of patients has markedly increased. Of these young patients (median age, 25 years), 53 were men, and 97 had consumed caffeine in tablet form. Estimated caffeine doses (n=93) ranged from 1.2 to 82.6 g (median, 7.2 g). Serum caffeine levels on admission (n=17) ranged from 2.0 to 530.0 μg/mL (median level, 106.0 μg/mL). Common abnormal vital signs and laboratory data on admission included tachypnea, tachycardia, depressed consciousness, hypercreatinekinasemia, hyperglycemia, hypokalemia, hypophosphatemia, and hyperlactatemia. Common signs and symptoms in the clinical course included nausea, vomiting, excitement/agitation, and sinus tachycardia. Seven patients (6.9%) who had consumed ≥6.0 g of caffeine, or whose serum caffeine levels on admission were ≥200 μg/mL, developed cardiac arrest. Ninety-seven patients (96.0%) recovered completely, but 3 patients (3.0%) died. Conclusion The present analysis of data from more than 100 emergency patients revealed clinical features of moderate to fatal caffeine poisoning. We recommend highlighting the toxicity risks associated with ingesting highly caffeinated tablets.