Dose-dependent pharmacokinetics and psychomotor effects of caffeine in humans

Energy drinks and alcohol: links to alcohol behaviors and consequences across 56 days

PURPOSE

To examine short-term consequences associated with consuming alcohol and energy drinks compared with consuming alcohol without energy drinks.

METHODS

A longitudinal measurement-burst design (14-day bursts of daily surveys in four consecutive college semesters) captured both within-person variation across occasions and between-person differences across individuals. The analytic sample of late adolescent alcohol users included 4,203 days with alcohol use across up to four semesters per person from 508 college students.

RESULTS

Adding energy drink use to a given day with alcohol use was associated with an increase in number of alcoholic drinks, a trend toward more hours spent drinking, elevated estimated blood alcohol content (eBAC), a greater likelihood of subjective intoxication, and more negative consequences of drinking that day. After controlling for eBAC, energy drink use no longer predicted subjective intoxication but was still associated with a greater number of negative consequences.

CONCLUSIONS

The consumption of energy drinks may lead to increases in alcohol consumption and, after controlling for eBAC, negative consequences. Use of energy drinks plus alcohol represents an emerging threat to public health.

Caffeine intoxication successfully treated by hemoperfusion and hemodialysis

Caffeine is an easily available drug which is generally regarded as being safe. However, it can lead to a lethal outcome in severe cases of caffeine intoxication. We herein report a case of a 32-year-old man who ingested approximately 15.6 g of caffeine in a suicide attempt. He suffered from sustained ventricular tachycardia despite conservative treatment. Therefore, we performed a combined therapy of hemoperfusion and hemodialysis which resulted in rapid improvement of the patient's ventricular tachycardia as well as a reduction of the patient's plasma caffeine level. To the best of our knowledge, this combination has not been previously reported to treat caffeine intoxication.

Psychostimulants and cognition: a continuum of behavioral and cognitive activation

Psychostimulants such as cocaine have been used as performance enhancers throughout recorded history. Although psychostimulants are commonly prescribed to improve attention and cognition, a great deal of literature has described their ability to induce cognitive deficits, as well as addiction. How can a single drug class be known to produce both cognitive enhancement and impairment? Properties of the particular stimulant drug itself and individual differences between users have both been suggested to dictate the outcome of stimulant use. A more parsimonious alternative, which we endorse, is that dose is the critical determining factor in cognitive effects of stimulant drugs. Herein, we review several popular stimulants (cocaine, amphetamine, methylphenidate, modafinil, and caffeine), outlining their history of use, mechanism of action, and use and abuse today. One common graphic depiction of the cognitive effects of psychostimulants is an inverted U-shaped dose-effect curve. Moderate arousal is beneficial to cognition, whereas too much activation leads to cognitive impairment. In parallel to this schematic, we propose a continuum of psychostimulant activation that covers the transition from one drug effect to another as stimulant intake is increased. Low doses of stimulants effect increased arousal, attention, and cognitive enhancement; moderate doses can lead to feelings of euphoria and power, as well as addiction and cognitive impairment; and very high doses lead to psychosis and circulatory collapse. This continuum helps account for the seemingly disparate effects of stimulant drugs, with the same drug being associated with cognitive enhancement and impairment.

Characterization of cognitive dysfunction in Sjögren's syndrome patients

Sjögren's syndrome is an autoimmune disorder primarily affecting women, with decreased saliva and tear production as the principal characteristic. Cognitive, neurological, and psychiatric disorders also are associated with Sjögren's. The present study addressed the hypothesis that patients with Sjögren's syndrome differ significantly from matched controls in the prevalence and impact of a number of neuropsychiatric abnormalities. Sjögren's patients and controls (n = 37 per group) underwent medical and psychiatric evaluation, demographic assessments, quality of life and symptom evaluation, and extensive testing of cognitive function and memory. Patients and controls were closely matched for age, gender distribution, verbal IQ, marital status, educational level, employment status, and current/past medical or psychiatric history. On most subjective self-ratings, Sjögren's patients reported greater fatigue, impaired physical functioning, feeling depressed, and autonomic symptomatology compared to controls. Impaired memory was described mainly as loss of thought continuity in the midst of a task or activity. However, the majority of objective measures of cognition, psychomotor function, and memory showed minimal differences between groups. Sjögren's patients rate themselves as impaired on multiple ratings of emotional, cognitive, and physical function, but objective measures of cognition reveal fewer substantive differences between patients and matched controls. Sjögren's patients perceive deteriorated physical function over time, but they achieve a level of functioning comparable to controls despite the burden of their illness.

Gender differences in pharmacokinetics and pharmacodynamics of zolpidem following sublingual administration

The effect of dose and gender on the pharmacokinetics (PK) and pharmacodynamics (PD) of zolpidem after administration of a buffered zolpidem sublingual tablet (ZST; Intermezzo®, Purdue Pharma L.P., Stamford, CT, USA) was evaluated in healthy non-elderly male and female volunteers. Subjects received a single morning dose of ZST (1.0, 1.75, and 3.5 mg) or placebo in a four-way crossover study. In male and female subjects zolpidem PK were linear, with area under the curve (AUC) proportional to dose, and apparent oral clearance and elimination half-life independent of dose. However, AUC averaged 40% to 50% higher in females than in males receiving the same dose. The gender effect was incompletely explained by body weight. In females, ZST produced PD changes consistent with benzodiazepine agonist effects, particularly at the 3.5-mg dose. For several PD variables, PD effects were significantly related to plasma zolpidem concentrations when data were aggregated across subjects. However, there was variability in response among individuals. In males, PD effects of zolpidem seldom differed from placebo regardless of plasma concentration. The findings confirm that zolpidem clearance is lower in females than in males. PD effects of zolpidem from ZST are greater in female subjects, due to a combination of higher plasma concentrations and greater intrinsic sensitivity.

Evaluation of a new computerized psychometric test battery: Effects of zolpidem and caffeine

Objective:

To evaluate the effects of centrally active drugs using a new indigenously developed automated psychometric test system and compare the results with that obtained using pencil- and paper-based techniques.

Materials and Methods:

The tests were standardized in 24 healthy participants. Reproducibility of the test procedure was evaluated by performing the tests by a single experimenter on two occasions (interday reproducibility). To evaluate the sensitivity of the tests, the effects of zolpidem (5 mg) and caffeine (500 mg) versus placebo were studied in 24 healthy participants in a randomized, double-blind three-way crossover design.

Results:

Psychometric tests were performed at baseline and at 1, 2, and 3 h after administration of study medication. The effects of zolpidem and caffeine on the psychomotor performance were most pronounced 1 h after administration. At this time, a significant impairment of performance in the simple reaction test (SRT), choice discrimination test (CDT), digit symbol substitution test (DSST), digit vigilance test (DVT), and card sorting test (CST) was observed with zolpidem. In contrast, caffeine showed a significant improvement in performance in CDT and DVT only.

Conclusion:

The results suggest that the tests of the computerized system are more sensitive and reliable then the pencil and paper tests in detecting the effects of central acting agents and are suitable for use in clinical areas to conduct studies with patients.

A pharmacometric approach to investigate the impact of methylxanthine abstinence and caffeine consumption on CYP1A2 activity

This study aimed to investigate the impact of methylxanthine abstinence (MA) periods on CYP1A2 activity in individuals with varying levels of caffeine consumption through development of a population pharmacokinetic model of caffeine and its major metabolite paraxanthine. This study developed and evaluated a mixed-effects pharmacokinetic model for caffeine and paraxanthine concentration-time data derived from a sequential single-dose cross-over study in healthy male volunteers (n = 30) who received oral 100 mg caffeine doses. Participants received caffeine with and without a MA period. Participants were classified as low (0-100 mg/d), medium (100-200 mg/d), or high (>200 mg/d) caffeine consumers (LCCs, MCCs, or HCCs, respectively). All caffeine and paraxanthine concentration-time data were simultaneously modeled. Caffeine pharmacokinetics was described by a two-compartment model with first-order absorption and two first-order elimination pathways. Paraxanthine was described by a one-compartment model with first-order absorption and elimination. Among LCCs (n = 16) and MCCs (n = 9), there was no difference in the mean (95% confidence interval) total apparent caffeine clearance (CL) between the MA period [LCCs: 6.88 (5.61-8.16 l/h); MCCs: 10.09 (7.57-12.60 l/h)] versus the no MA period [LCCs: 6.22 (4.97-7.46 l/h); MCCs: 9.68 (7.12-12.24 l/h)]. The mean CL among HCCs (n = 5) was considerably higher in the MA period [10.48 (5.62-15.33 l/h)] compared with the no MA period [6.30 (3.40-9.20 l/h)] (P < 0.05). The decrease in CL in the no MA period among HCC appears to be due to alternative caffeine elimination pathways, rather than CYP1A2.

The Janus face of caffeine

Caffeine is certainly the psychostimulant substance most consumed worldwide. Over the past years, chronic consumption of caffeine has been associated with prevention of cognitive decline associated to aging and mnemonic deficits of brain disorders. While its preventive effects have been reported extensively, the cognitive enhancer properties of caffeine are relatively under debate. Surprisingly, there are scarce detailed ontogenetic studies focusing on neurochemical parameters related to the effects of caffeine during prenatal and earlier postnatal periods. Furthermore, despite the large number of epidemiological studies, it remains unclear how safe is caffeine consumption during pregnancy and brain development. Thus, the purpose of this article is to review what is currently known about the actions of caffeine intake on neurobehavioral and adenosinergic system during brain development. We also reviewed other neurochemical systems affected by caffeine, but not only during brain development. Besides, some recent epidemiological studies were also outlined with the control of "pregnancy signal" as confounding variable. The idea is to tease out how studies on the impact of caffeine consumption during brain development deserve more attention and further investigation.

Caffeine at Moderate Doses Can Inhibit Acupuncture-Induced Analgesia in a Mouse Model of Postoperative Pain

BACKGROUND

The use of acupuncture in the treatment of pain conditions has been extensively investigated. However, the influence of dietary ingredients on acupuncture-induced analgesia (AA) remains unexplored. Recently, the role of adenosine receptors in AA has been shown, and caffeine, one of the world's most commonly consumed dietary ingredients, is an antagonist of these receptors. In this study, the postincisional pain model was used to investigate caffeine's influence on AA.

METHOD

Mice submitted to plantar incision surgery were treated with acupuncture needling after administration of acute or chronic caffeine. Acupuncture needling was performed using two different types of stimuli, manual acupuncture and electroacupuncture bilaterally in the acupoint SP6.

RESULTS

We found that acute preadministration of caffeine (10 mg/kg, i.p.) completely reversed AA in both types of acupuncture. In the chronic preadministration, we used two doses that mimicked the average daily caffeine consumption in Western countries and China. Interestingly, the Western dose of caffeine (70 mg/kg/day) administered during 8 days in the drinking water reversed AA and the Chinese dose (4 mg/kg/day) administered during the same period did not.

CONCLUSIONS

These results indicate that the use of caffeine can inhibit the analgesic effect of different forms of acupuncture. In addition, our findings suggest that doses of caffeine relevant to dietary human intake levels could be a confounding factor in the context of acupuncture research.

Caffeinated Alcoholic Beverages - An Emerging Trend in Alcohol Abuse

Alcohol use disorders are pervasive in society and their impact affects quality of life, morbidity and mortality, as well as individual productivity. Alcohol has detrimental effects on an individual’s physiology and nervous system, and is associated with disorders of many organ and endocrine systems impacting an individual’s health, behavior, and ability to interact with others. Youth are particularly affected. Unfortunately, adolescent usage also increases the probability for a progression to dependence. Several areas of research indicate that the deleterious effects of alcohol abuse may be exacerbated by mixing caffeine with alcohol. Some behavioral evidence suggests that caffeine increases alcohol drinking and binge drinking episodes, which in turn can foster the development of alcohol dependence. As a relatively new public health concern, the epidemiological focus has been to establish a need for investigating the effects of caffeinated alcohol. While the trend of co-consuming these substances is growing, knowledge of the central mechanisms associated with caffeinated ethanol has been lacking. Research suggests that caffeine and ethanol can have additive or synergistic pharmacological actions and neuroadaptations, with the adenosine and dopamine systems in particular implicated. However, the limited literature on the central effects of caffeinated ethanol provides an impetus to increase our knowledge of the neuroadaptive effects of this combination and their impact on cognition and behavior. Research from our laboratories indicates that an established rodent animal model of alcoholism can be extended to investigate the acute and chronic effects of caffeinated ethanol.

Physiologic responses to a thermogenic nutritional supplement at rest, during low-intensity exercise, and during recovery from exercise in college-aged women

This study examined acute physiologic responses to a thermogenic nutritional supplement at rest, during exercise, and during recovery from exercise in women. Twelve women (mean ± SD age, 22.9 ± 3.1 years) were recruited for this randomized, double-blinded, placebo-controlled, crossover study. Each testing session consisted of 4 phases: 30 min of presupplementation resting, followed by the ingestion of the placebo or thermogenic nutritional supplement; 50 min of postsupplementation resting; 60 min of walking (at 3.2-4.8 km·h(-1)); and 50 min of postexercise resting. Energy expenditure (EE), oxygen consumption, respiratory exchange ratio (RER), oxygen (O2) pulse, and heart rate (HR) values were recorded during all 4 phases. Systolic (SBP) and diastolic (DBP) blood pressure were recorded during the rest, postsupplementation, and postexercise recovery phases; ratings of perceived exertion (RPE) were recorded only during exercise. There were no significant differences for EE, oxygen consumption, O2 pulse, HR, SBP, or DBP between the supplement and placebo during the presupplementation resting or postsupplementation phases. The RER, however, was higher with the supplement at 30 min postsupplementation. During exercise, EE and O2 pulse were 3%-6% greater with the supplement than placebo; there were no significant differences in RPE. Postexercise, EE, oxygen consumption, and DBP were 3%-7% greater with the supplement than placebo. These findings suggest that a thermogenic nutritional supplement, when combined with exercise, increases metabolic rate but has no effect on the perception of effort and results in only minimal changes in cardiovascular function.

Caffeine intake reduces sleep duration in adolescents

In our study, we hypothesized that higher caffeine intake would be associated with lower sleep duration among 13-year-old adolescents. In addition, we aimed to identify food sources of caffeine intake in this sample. Eligible participants were adolescents who were born in 1990 and attended school in Porto, Portugal, in 2003/2004. Self-administered questionnaires were used, and diet was evaluated using a food frequency questionnaire. From the 2160 eligible participants, only 1522 with valid information regarding their diet were included in this study. In our sample, the median intake of caffeine was 23.1 mg/d, with soft drinks being the major source. Ice tea presented the highest median (25th-75th percentiles) contribution (33.1% [14.0-52.1]), followed by cola (21.1% [6.4-37.6]). Regarding cocoa products, chocolate bars presented a median contribution of 5.1% (1.0-14.0), and snacks containing chocolate had a contribution of 3.0% (0.5-7.2). Coffee and tea presented a negligible contribution. Adolescents who reported less sleep duration and those who spent more time watching TV during the weekend had a significantly higher caffeine intake. Overall, boys had higher intakes of caffeine from soft drinks, and private school attendees, those who had parents with more education, who reported less television viewing time and had lower body mass index presented higher intakes of caffeine from chocolate. Considering sleeping more than 9.5 hours as a reference class, for each increase of 10 mg/d in caffeine intake, we found that the odds ratio of sleeping 8.5 hours or less was 1.12 (95% confidence interval, 1.06-1.19). Our results support the hypothesis that caffeine intake was inversely associated with sleep duration in adolescents.

Dynamics and Kinetics of a Modified-Release Formulation of Zolpidem: Comparison With Immediate-Release Standard Zolpidem and Placebo

Modified-release (MR) zolpidem was developed to maintain effective plasma concentrations during the 3- to 6-hour post-dosage interval, corresponding to the middle portion of the typical sleep interval. Modified-release zolpidem (12.5 mg), standard immediate-release (IR) zolpidem (10 mg), and placebo were compared in a double-blind, single-dose, 3-way crossover daytime study of healthy volunteers (n = 70 completers). Effect areas for electroencephalographic beta amplitude during 0 to 8 hours and 3 to 6 hours after dosage were greater for MR compared to IR (P < .001). The digit-symbol substitution test and sedation rating scales behaved similarly. MR and IR did not differ in effects at 8 hours post-dosage nor in halflife or clearance. Time of peak plasma concentration (tmax) was significantly longer for MR (2.4 vs 2.0 hours, P < .004), and dose-normalized peak plasma concentration (Cmax) was lower (12.2 vs 14.0 ng/mL/mg, P < .001). MR zolpidem also had greater area under the plasma concentration curve (AUC) during the 3- to 6-hour interval (P < .001). Thus, MR zolpidem produces sustained plasma levels compared to IR, with resulting enhancement of pharmacodynamic effects in the 3- to 6-hour post-dosage interval.

Energy drink use and adverse effects among emergency department patients

Energy drink usage is common and contains caffeine or other stimulants. We evaluated demographics, prevalence, reasons and adverse effects with consuming energy beverages. Cross-sectional study of a convenience sample of patients recruited from two San Diego Emergency Departments from January to December 2009. One-thousand-two-hundred-ninety-eight subjects participated of which 52.6% were male. Ethnicity: Caucasian 48.3%, African American 17%, Hispanic 18%, Other 16.7%. Age ranges: 18-29 years (38.4%), 30-54 years (49.6%) and greater than 55 years (12%). Reasons for use: 57% to "increase energy", 9.5% for studying/work projects, 2.4% while prolonged driving, improve sports performance 2%, with ethanol 6.3%, "other" reasons 22.1%. Adverse reactions reported by 33.5% (429) patients. Two-hundred-eighty report feeling "shaky/jittery", insomnia 136, palpitations 150, gastrointestinal upset 82, headache 68, chest pain 39, and seizures in 6. Eighty-five patients reported co-ingestion with illicit "stimulants" including cocaine and methamphetamine. We identified one-third of patients reported at least one adverse effect. Whilst most were not severe, a small number were serious e.g., seizures. In addition, some report purposely ingesting with illicit drugs.

Caffeine counteracts impairments in task-oriented psychomotor performance induced by chlorpheniramine: a double-blind placebo-controlled crossover study

This study aimed to evaluate the effects of chlorpheniramine on psychomotor performance and the counteracting effects of caffeine on those sedative antihistamine actions. Sixteen healthy young men participated in this study. Using a double-blind placebo-controlled crossover design, each subject was administered one of the following conditions in a random order with a one-week interval: 'placebo-placebo', '4 mg of chlorpheniramine-placebo', 'placebo-200 mg of caffeine' or '4 mg of chlorpheniramine-200 mg of caffeine'. Before and after the treatments, psychomotor functions were assessed using a battery of tests. Additionally, subjective responses were assessed using a visual analogue scale (VAS). Psychomotor performance changed over time in different ways according to the combination of study medications. In the 'chlorpheniramine-placebo' condition, reaction times of the compensatory tracking task were significantly impaired compared with the other three conditions. In addition, the number of omission errors of the continuous performance test were significantly greater compared with the 'placebo-caffeine' condition. However, the response pattern of the 'chlorpheniramine-caffeine' condition was not significantly different from that of the 'placebo-placebo' condition. Changes of VAS for sleepiness were significantly greater in the 'chlorpheniramine-placebo' condition compared with the other three conditions. In conclusion, chlorpheniramine significantly increases subjective sleepiness and objectively impairs psychomotor performance. However, caffeine counteracts these sedative effects and psychomotor impairments.

Crude caffeine reduces memory impairment and amyloid β(1-42) levels in an Alzheimer's mouse model

Alzheimer's disease (AD), a chronic neurodegenerative disorder associated with the abnormal accumulations of amyloid β (Aβ) peptide and oxidative stress in the brain, is the most common form of dementia among the elderly. Crude caffeine (CC), a major by-product of the decaffeination of coffee, has potent hydrophilic antioxidant activity and may reduce inflammatory processes. Here, we showed that CC and pure caffeine intake had beneficial effects in a mouse model of AD. Administration of CC or pure caffeine for 2months partially prevented memory impairment in AD mice, with CC having greater effects than pure caffeine. Furthermore, consumption of CC, but not pure caffeine, reduced the Aβ(1-42) levels and the number of amyloid plaques in the hippocampus. Moreover, CC and caffeine protected primary neurons from Aβ-induced cell death and suppressed Aβ-induced caspase-3 activity. Our data indicate that CC may contain prophylactic agents against the cell death and the memory impairment in AD.

A case of acute suicidality following excessive caffeine intake

Energy and stimulant drinks which contain caffeine provide enlivening effects, reduce fatigue and improve concentration and endurance. However, consumers may also experience physical and psychological side effects as a result of excessive consumption of caffeine within these drinks. Caffeine is known to exacerbate or induce some psychiatric conditions such as anxiety, panic attacks, psychosis and mania. Here we discuss a case of acute suicidality following sleep deprivation after the excessive consumption of a popular energy drink. We are concerned that such widely available stimulant drinks should contain health warnings or advice regarding moderating consumption.

Toxicity of energy drinks

PURPOSE OF REVIEW

'Energy drinks', 'energy shots' and other energy products have exploded in popularity in the past several years; however, their use is not without risk. Caffeine is the main active ingredient in energy drinks, and excessive consumption may acutely cause caffeine intoxication, resulting in tachycardia, vomiting, cardiac arrhythmias, seizures, and death. The effects of chronic high-dose caffeine intake in children and adolescents are unknown. Caffeine may raise blood pressure, disrupt adolescent sleep patterns, exacerbate psychiatric disease, cause physiologic dependence, and increase the risk of subsequent addiction.

RECENT FINDINGS

Coingestion of caffeine and ethanol has been associated with increased risk-taking behaviors, harm to adolescent users, impaired driving, and increased use of other illicit substances. The toxicity of ingredients often present in energy drinks, such as taurine, niacin, and pyridoxine, is less well defined. Recent and significant literature describing adverse events associated with energy drink use are reviewed.

SUMMARY

Although prior studies have examined the effects of caffeine in adolescents, energy drinks should be considered a novel exposure. The high doses of caffeine, often in combination with ingredients with unknown safety profiles, mandates urgent research on the safety of energy drink use in children and adolescents. Regulation of pediatric energy drink use may be a necessary step once the health effects are further characterized.

Haemodialysis in massive caffeine intoxication

Caffeine is the most widely consumed psychoactive substance worldwide. Intoxication causes central nervous system and haemodynamic complications, which have significant mortality rates. We report the case of a 39-year-old woman who ingested ∼0.5 mol (100 g) of pure caffeine, leading to a peak serum concentration of 2.95 mmol/L (574 mg/L). Three consecutive haemodialysis sessions caused serum caffeine reduction rates of 66, 46 and 45%, indicating that the unbound caffeine fraction is not dose linear in this high serum caffeine concentration range. Aggressive and repeated haemodialysis sessions may be of benefit in cases of severe caffeine intoxication.

Modeling caffeine concentrations with the Stanford Caffeine Questionnaire: preliminary evidence for an interaction of chronotype with the effects of caffeine on sleep

OBJECTIVE

To examine the validity of a novel caffeine intake questionnaire and to examine the effects of caffeine on sleep in college students.

METHODS

One-week, ad libitum behavior of 50 university students (28 female, 22 male; aged 20.9 ± 1.78 years) was examined with sleep logs, wrist actigraphy, and a novel daily questionnaire assessing caffeine intake at different times of day. Saliva samples were collected for caffeine assessment (questionnaire validation) and DNA extraction, and for analysis of a single nucleotide polymorphism in the adenosine receptor 2A (ADORA2A) gene.

RESULTS

The caffeine questionnaire was able to accurately predict salivary concentrations of caffeine (R(2) = 0.41, P<0.001). Estimations of integrated salivary caffeine concentration during sleep were correlated with wake after sleep onset (WASO) most strongly in morning-type individuals (R(2) = 0.49; P<0.001, ANOVA), less so in intermediate chronotypes (R(2) = 0.16; P<0.001, ANOVA), and not significantly in evening-types (R(2) = 0.00098; P = 0.13, ANOVA). Using multivariate modeling methods we found that the ADORA2A genotype did not moderate the effects of caffeine on WASO, but did independently alter WASO such that those with the CC genotype had nearly three-times as much WASO as those with CT or TT.

CONCLUSIONS

Our questionnaire was able to accurately predict salivary caffeine concentrations and helped to describe a novel relationship between the effects of caffeine on sleep and genotype and chronotype.

Hemodynamic and hematologic profile of healthy adults ingesting dietary supplements containing 1,3-dimethylamylamine and caffeine

BACKGROUND

1,3-dimethylamylamine (a constituent of geranium), alone and in combination with caffeine, is widely used within dietary supplements. We have recently determined the hemodynamic effects of 1,3-dimethylamylamine and caffeine alone and in combination, using a single ingestion study. However, no study has determined the hemodynamic effects of these ingredients following chronic use. Moreover, no study has determined the effects of these ingredients on bloodborne variables related to health and safety. Therefore, the purpose of this investigation was to assess the hemodynamic and hematologic profile of two different dietary supplements containing 1,3-dimethylamylamine and caffeine (in addition to other ingredients), before and after two weeks of daily intake.

METHODS

7 men (24.9 ± 4.2 yrs) ingested the dietary supplement Jack3d™, while 4 men and 2 women (22.5 ± 1.8 yrs) ingested the dietary supplement OxyELITE Pro™ once per day for two weeks. On days 1 and 15, resting heart rate (HR), systolic (SBP), and diastolic (DBP) blood pressure were measured and rate pressure product (RPP) was calculated. Fasting blood samples were analyzed for complete blood counts, comprehensive metabolic panel, and lipid panel. These tests were done prior to ingestion of supplement. On days 1 and 15 following blood collection, subjects ingested the assigned supplement (2 servings) and HR, SBP, DBP, and RPP were recorded at 30, 60, 90, and 120 minutes post-ingestion.

RESULTS

After 14 days of treatment, resting HR, SBP, DBP, and RPP were not increased (P > 0.05). No significant changes were noted in any measured bloodborne variable, with the exception of an increase in fasting blood glucose with ingestion of Jack3d™ (P = 0.02). In response to acute intake of the supplements, HR, DBP, and RPP were not increased statistically (P > 0.05). SBP was increased with OxyELITE Pro™ (P = 0.03), but not with Jack3d™ (P = 0.09). Compared to pre-ingestion and in general, both supplements resulted in an increase in SBP, DBP, and RPP from 5%-15%, with a peak occurring at the 60 or 90 minute post-ingestion time.

CONCLUSION

Acute ingestion of OxyELITE Pro™, but not Jack3d™, results in an increase in SBP. Chronic intake of two servings per day of OxyELITE Pro™ or Jack3d™ over a 14 day period does not result in an elevation in resting HR, SBP, DBP, or RPP. No significant changes are noted in any measured bloodborne variable following 14 days of ingestion, with the exception of blood glucose with Jack3d™. Longer term intervention studies inclusive of larger sample sizes are needed to extend these findings.

Influences of audio-visual environments on feelings of deliciousness during having sweet foods: an electroencephalogram frequency analysis study

Feelings of deliciousness during having foods are mainly produced by perceptions of sensory information extracted from foods themselves, such as taste and olfaction. However, environmental factors might modify the feeling of deliciousness. In the present study, we investigated how the condition of audio-visual environments affects the feeling of deliciousness during having sweet foods. Electroencephalograms (EEGs) were recorded from the frontal region of the scalp of healthy participants under virtual scenes of tearoom and construction work, respectively. The participants were asked to rate deliciousness after the recordings. Frequency analyses were performed from the EEGs. During having the foods, occupancy rates of beta frequency band between tearoom scenes and construction work scenes were markedly different, but not in other frequency bands. During having no food, in contrast, there was no difference of occupancy rates in respective frequency bands between the two different scenes. With regard to deliciousness during having sweet foods, all participants rated high scores under the scenes of tearoom than those under the scenes of construction work. Interestingly, there is a positive correlation between occupancy rates of beta frequency band and scores of deliciousness. These findings suggest that comfortable audio-visual environments play an important role in increasing the feeling of deliciousness during having sweet foods, in which beta frequency rhythms may be concerned with producing comprehensive feelings of deliciousness.

The effect of 90 day administration of a high dose vitamin B-complex on work stress

OBJECTIVE

Occupational stress is increasing in Western societies and the impact is significant at a personal, organisational and community level. The present study examined for the first time the efficacy of 3 months administration of two forms of high dose vitamin B complex on mood and psychological strain associated with chronic work stress.

METHOD

Sixty participants completed the 3-month, double-blind, randomised, placebo-controlled trial in which personality, work demands, mood, anxiety and strain were assessed.

RESULTS

After individual differences in personality and work demands were statistically controlled, the vitamin B complex treatment groups reported significantly lower personal strain and a reduction in confusion and depressed/dejected mood after 12 weeks. There were no treatment-related changes in other measures of mood and anxiety.

DISCUSSION

The results of the study are consistent with two previous studies examining multivitamin supplementation and personal (non-work) feelings of strain and suggestive of significant decreases in the experience of workplace stress after 90 day supplementation of a B multivitamin.

CONCLUSION

Given the direct and indirect costs of workplace stress, these findings point to the utility of a cost-effective treatment for the mood and psychological strain effects of occupational stress. These findings may have important personal health, organisational and societal outcomes given the rising cost and incidence of workplace stress.

Purinergic signalling: from normal behaviour to pathological brain function

Purinergic neurotransmission, involving release of ATP as an efferent neurotransmitter was first proposed in 1972. Later, ATP was recognised as a cotransmitter in peripheral nerves and more recently as a cotransmitter with glutamate, noradrenaline, GABA, acetylcholine and dopamine in the CNS. Both ATP, together with some of its enzymatic breakdown products (ADP and adenosine) and uracil nucleotides are now recognised to act via P2X ion channels and P1 and P2Y G protein-coupled receptors, which are widely expressed in the brain. They mediate both fast signalling in neurotransmission and neuromodulation and long-term (trophic) signalling in cell proliferation, differentiation and death. Purinergic signalling is prominent in neurone-glial cell interactions. In this review we discuss first the evidence implicating purinergic signalling in normal behaviour, including learning and memory, sleep and arousal, locomotor activity and exploration, feeding behaviour and mood and motivation. Then we turn to the involvement of P1 and P2 receptors in pathological brain function; firstly in trauma, ischemia and stroke, then in neurodegenerative diseases, including Alzheimer's, Parkinson's and Huntington's, as well as multiple sclerosis and amyotrophic lateral sclerosis. Finally, the role of purinergic signalling in neuropsychiatric diseases (including schizophrenia), epilepsy, migraine, cognitive impairment and neuropathic pain will be considered.

Comparison of caffeine-induced locomotor activity between adolescent and adult rats

Caffeine is the psychostimulant drug most consumed in the world. This drug is present in food, beverages and medicines marketed for individuals of all ages. In spite of this, caffeine effects on adolescents are poorly understood. The aim of this study was to evaluate the differences on caffeine-induced locomotor stimulant or depressant effects in adolescent and adult rats. Adolescent (37-40 days old) or adult (70-74 days old) Wistar rats were tested for stimulant and depressant caffeine effects in two different experiments. The first was designed to evaluate the locomotor effect of caffeine in habituated rats. To this end, rats were previously habituated to test environment and had their locomotor activity registered following i.p. injections of vehicle or caffeine (3, 10, 30, 60 or 120 mg/kg). In the second experiment adolescent or adult rats were not habituated to the test environment and their locomotor activity was registered following i.p. injections of vehicle or caffeine (30, 60 or 120 mg/kg). In both experiments caffeine-induced a biphasic effect, with stimulation in small to moderate drug doses and no effect or locomotor depression in higher caffeine doses. Moreover, caffeine-induced locomotor stimulation was higher in adolescent than adult rats. Also, locomotor depression was only revealed in adult rats non-habituated to the test environment. These results suggest that adult and adolescent respond differently to caffeine indicating the need of more studies on the effects of caffeine in animals' models of adolescence.

Atrial fibrillation in healthy adolescents after highly caffeinated beverage consumption: two case reports

INTRODUCTION

Energy drinks and highly caffeinated drinks comprise some of the fastest growing products of the beverage industry, often targeting teenagers and young adults. Cardiac arrhythmias in children related to high caffeine consumption have not been well described in the literature. This case series describes the possible association between the consumption of highly caffeinated drinks and the subsequent development of atrial fibrillation in the adolescent population.

CASE PRESENTATIONS

We report the cases of two Caucasian adolescent boys of 14 and 16 years of age at the time of presentation, each without a significant cardiac history, who presented with palpitations or vague chest discomfort or both after a recent history of excessive caffeine consumption. Both were found to have atrial fibrillation on electrocardiogram; one patient required digoxin to restore a normal sinus rhythm, and the other self-converted after intravenous fluid administration.

CONCLUSION

With the increasing popularity of energy drinks in the pediatric and adolescent population, physicians should be aware of the arrhythmogenic potential associated with highly caffeinated beverage consumption. It is important for pediatricians to understand the lack of regulation in the caffeine content and other ingredients of these high-energy beverages and their complications so that parents and children can be educated about the risk of cardiac arrhythmias with excessive energy drink consumption.

Caffeine (1, 3, 7-trimethylxanthine) in foods: a comprehensive review on consumption, functionality, safety, and regulatory matters

Caffeine ranks as one of the top most commonly consumed dietary ingredients throughout the world. It is naturally found in coffee beans, cacao beans, kola nuts, guarana berries, and tea leaves including yerba mate. The total daily intake, as well as the major source of caffeine varies globally; however, coffee and tea are the 2 most prominent sources. Soft drinks are also a common source of caffeine as well as energy drinks, a category of functional beverages. Moderate caffeine consumption is considered safe and its use as a food ingredient has been approved, within certain limits, by numerous regulatory agencies around the world. Performance benefits attributed to caffeine include physical endurance, reduction of fatigue, and enhancing mental alertness and concentration. Caffeine has also been recently linked to weight loss and consequent reduction of the overall risks for developing the metabolic syndrome. However, the caloric contribution of caffeine-sweetened beverages needs to be considered in the overall energy balance. Despite all these benefits the potential negative effects of excessive caffeine intake should also be considered, particularly in children and pregnant women.

Interrelations between plasma caffeine concentrations and neurobehavioural effects in healthy volunteers: model analysis using NONMEM

The objective was to develop a population pharmacokinetic-pharmacodynamic model of caffeine's psychomotor effects in healthy, non-habitual users of caffeine. Twenty Chinese males each received a single dose of 250 mg of caffeine orally. Plasma concentrations of caffeine were determined at various times within 24 h after dosing. The subjects' psychomotor performance was evaluated before and at various times after dosing by a test battery consisting of oculomotor assessment (saccadic velocity) as well as the computerised Swedish Performance Evaluation System. Nonlinear mixed-effects modelling to analyse the pharmacokinetic-pharmacodynamic relationships was performed using NONMEM. Model robustness was assessed by a nonparametric bootstrap. The results showed that caffeine caused significant improvements in psychomotor functioning. The time course of these effects was best described by pharmacokinetic/pharmacodynamic models involving an effect compartment. The transfer half-lives between plasma and effect site for different domains of psychomotor functioning were in the range 24.8-49.5 min. Evaluation of the final models showed close agreement between pairs of bootstrapped and final model parameter estimates (all differences<10%). These results provided the first suggestive evidence that caffeine effects on psychomotor performance occur after some time delay relative to changes in plasma caffeine concentration. The models for the neurobehavioural tests provided similar transfer half-lives between plasma and effect site.

Adenosine A1 and A2A receptors are not upstream of caffeine's dopamine D2 receptor-dependent aversive effects and dopamine-independent rewarding effects

Caffeine is widely consumed throughout the world, but little is known about the mechanisms underlying its rewarding and aversive properties. We show that pharmacological antagonism of dopamine not only blocks conditioned place aversion to caffeine, but also reveals dopamine blockade-induced conditioned place preferences. These aversive effects are mediated by the dopamine D(2) receptor, as knockout mice showed conditioned place preferences in response to doses of caffeine that C57Bl/6 mice found aversive. Furthermore, these aversive responses appear to be centrally mediated, as a quaternary analog of caffeine failed to produce conditioned place aversion. Although the adenosine A(2A) receptor is important for caffeine's physiological effects, this receptor seems only to modulate the appetitive and aversive effects of caffeine. A(2A) receptor knockout mice showed stronger dopamine-dependent aversive responses to caffeine than did C57Bl/6 mice, which partially obscured the dopamine-independent and A(2A) receptor-independent preferences. Additionally, the A(1) receptor, alone or in combination with the A(2A) receptor, does not seem to be important for caffeine's rewarding or aversive effects. Finally, excitotoxic lesions of the tegmental pedunculopontine nucleus revealed that this brain region is not involved in dopamine blockade-induced caffeine reward. These data provide surprising new information on the mechanism of action of caffeine, indicating that adenosine receptors do not mediate caffeine's appetitive and aversive effects. We show that caffeine has an atypical reward mechanism, independent of the dopaminergic system and the tegmental pedunculopontine nucleus, and provide additional evidence in support of a role for the dopaminergic system in aversive learning.

Caffeine fatalities--do sales restrictions prevent intentional intoxications?

OBJECTIVE

Caffeine is widely available in beverages and in different over-the-counter products, including tablets containing 100 mg caffeine. Because intentional fatal intoxications with caffeine occur, the maximum quantity of caffeine tablets that can be bought over the counter in a single purchase was restricted from 250 to 30 in Sweden in the year 2004. The objective of this article was to study the effect of this decision on the number of fatal caffeine intoxications.

METHOD

In Sweden 95% of all cases undergoing forensic autopsy are screened for a number of drugs including caffeine. All cases during January 1993-September 2009 with a caffeine concentration above 80 microg/g blood were recorded.

RESULTS

During the study period toxicological investigations were performed in 83,580 forensic autopsies. Caffeine contributed to the fatal outcome in 20 cases (0.02%). Thirteen (65%) of these fatalities occurred before the introduction of the sales restriction. However, no fatal intoxications where caffeine contributed to the cause of death was recorded between May 2007 and September 2009.

CONCLUSION

Overdoses of tablets containing caffeine can be fatal, suicides as well as accidents occur. Restricting the maximum quantity of caffeine tablets available over the counter seemed to be effective in preventing suicides because of caffeine although some time elapsed until the effect was noted. Further monitoring is required to ensure that the observed lower caffeine mortality is a sustained effect.

Neuroprotection by caffeine: time course and role of its metabolites in the MPTP model of Parkinson's disease

Epidemiological studies have raised the possibility of caffeine serving as a neuroprotective agent in Parkinson's disease (PD). This possibility has gained support from findings that dopaminergic neuron toxicity induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or other neurotoxins is attenuated by co-administration of caffeine in mice. Here we examined the time window of caffeine's neuroprotection as well as the effects of caffeine's metabolites (theophylline and paraxanthine) in the MPTP mouse model of PD. In the first experiment, caffeine pre-treatment (30 mg/kg ip) significantly attenuated MPTP-induced striatal dopamine depletion when it was given 10 min, 30 min, 1 h, or 2 h but not 6 h before MPTP (40 mg/kg ip) treatment. Meanwhile, caffeine post-treatment also significantly attenuated striatal dopamine loss when it was given 10 min, 30 min, 1 h or 2 h but not 4 h, 8 h or 24 h after MPTP injection. In the second experiment, both theophylline (10 or 20 mg/kg) and paraxanthine (10 or 30 mg/kg) administration (10 min before MPTP) significantly attenuated MPTP-induced dopamine depletion in mice, as did caffeine (10 mg/kg) treatment. Thus the metabolites of caffeine also provide neuroprotective effects in this mouse model of PD. The data suggest that if caffeine protects against putative toxin-induced dopaminergic neuron injury in humans, then precise temporal pairing between caffeine and toxin exposures may not be critical because the duration of neuroprotection by caffeine may be extended by protective effects of its major metabolites.

Energy Drinks: An Assessment of Their Market Size, Consumer Demographics, Ingredient Profile, Functionality, and Regulations in the United States

  The consumption of energy drinks is rapidly increasing, as demonstrated by their large market growth. The targeted demographic group is teenagers, young adults, 18 to 34 y old; although expansion into nontraditional markets is also occurring. It is claimed that energy drinks can offer an increased energy boost related to their ingredient profile of caffeine, taurine, herbal extracts, and vitamins. Research suggests that energy drink formulations, in addition to increasing energy utilization, may also improve mood, enhance physical endurance, reduce mental fatigue, and increase reaction time. However, in most cases, the corresponding mechanisms of action are not clear. In addition, concerns have been raised over their safety and with a currently weak regulatory environment, efforts need to be made to ensure consumer safety. The objective of this article is to review the current U.S. energy drink market with emphasis on its market size, target demographic, active ingredients, potential benefits, safety, and regulations.

Perazine at therapeutic drug concentrations inhibits human cytochrome P450 isoenzyme 1A2 (CYP1A2) and caffeine metabolism--an in vitro study

The aim of the present study was to estimate the inhibitory effect of perazine, a phenothiazine neuroleptic with piperazine structure in a side chain, on human CYP1A2 activity measured as a rate of caffeine 3-N- and 1-N-demethylation. Moreover, the influence of perazine on other caffeine metabolic pathways such as 7-N-demethylation (CYP1A2, CYP2C8/9, CYP3A4) and 8-hydroxylation (CYP3A4, CYP1A2, CYP2C8/9) was also determined. The Dixon analysis showed that in both human liver microsomes and Supersomes CYP1A2 perazine potently and to a similar degree inhibited caffeine 3-N-demethylation (K(i) = 3.5 microM) and 1-N-demethylation (K(i) = 5 microM). Perazine moderately diminished the rate of caffeine 7-N-demethylation in Supersomes CYP1A2 (K(i) = 11.5 microM) and liver microsomes (K(i) = 20 microM), and attenuated C-8-hydroxylation (K(i) = 15.5 microM) in Supersomes CYP1A2. On the other hand, perazine weakly inhibited caffeine C-8-hydroxylation in liver microsomes (K(i) = 98 microM). About 80% of basal CYP1A2 activity was reduced by the therapeutic concentrations of perazine (5-10 microM). The obtained results show that perazine at its therapeutic concentrations is a potent inhibitor of human CYP1A2. Hence, taking account of CYP1A2 contribution to the metabolism of endogenous substances (steroids), drugs (xanthine derivatives, phenacetin, propranolol, imipramine, phenothiazine neuroleptics, clozapine) and carcinogenic compounds, the inhibition of CYP1A2 by perazine may be of physiological, pharmacological and toxicological importance.

A comparison of the effects of caffeine following abstinence and normal caffeine use

RATIONALE

Caffeine typically produces positive effects on mood and performance. However, tolerance may develop following habitual use, and abrupt cessation can result in withdrawal symptoms, such as fatigue. This study investigated whether caffeine has a greater stimulant effect in a withdrawn state compared to a normal caffeinated state, among moderate daily caffeine consumers.

MATERIALS AND METHODS

Using a within-subjects design, 17 caffeine consumers (mean +/- sd = 375 +/- 101 mg/day) ingested placebo or caffeine (250 mg) following 30-h of caffeine abstention or normal dietary caffeine use on four separate days. Self-reported mood and performance on choice reaction time, selective attention, and memory tasks were measured.

RESULTS

Caffeine had a greater effect on mood and choice reaction time in the abstained state than in the normal caffeinated state, but caffeine improved selective attention and memory in both states.

CONCLUSIONS

Although improvements in mood and reaction time may best explained as relief from withdrawal symptoms, other performance measures showed no evidence of withdrawal and were equally sensitive to an acute dose of caffeine in the normal caffeinated state.

Caffeine effects on resting-state arousal in children

From previous work in our laboratory, increases in skin conductance level (SCL), together with global (across-scalp) decreases in electroencephalogram (EEG) alpha power and increases in alpha frequency, are useful indices of arousal increase, and here we sought to identify changes in these indices with caffeine ingestion in children. We explored the effects of a single oral dose of caffeine (80 mg) in a randomised double-blind placebo-controlled repeated-measures cross-over study. Thirty healthy children aged between 8 and 13 years (mean age 10.5 years; 11 females) participated in two sessions, 1 week apart. EEG and SCL from a 3 min eyes-closed epoch, commencing approximately 30 min after ingestion of caffeine or placebo, were examined. Caffeine was associated with increased SCL, and a global reduction in EEG power in the theta and alpha bands, as well as topographically-focused reductions in delta and beta power, and a focal increase in alpha frequency. Only global alpha level demonstrated the expected inverse relationship with SCL in both placebo and caffeine conditions. These results are generally consistent with recent electrodermal and EEG studies of arousal. Together with our previous adult data, they indicate that caffeine can be used to increase arousal in both adults and children, without the potential confounds associated with varying task demands. Caffeine appears useful as a simple tool for manipulating arousal in studies exploring its role in physiological and behavioural functioning. This may be helpful in determining the role of hypothetical arousal anomalies in syndromes such as attention-deficit/hyperactivity disorder.

The Effects of Ginseng, Ephedrine, and Caffeine on Cognitive Performance, Mood and Energy

A variety of claims regarding the purported energy-enhancing properties of nutritional supplements and food constituents have recently been made. It appears that the supplements most frequently associated with such assertions are ginseng, ephedrine, and caffeine. Claims of increased energy are difficult to evaluate objectively because their meaning is not usually defined or specified. Often it is not clear whether the claims refer to physical or mental energy or both. Furthermore, an agreed upon scientific definition of either physical or mental energy enhancement does not exist. In spite of obvious differences in what the term physical energy, as opposed to mental energy implies, there is no clear scientific consensus on whether there is a difference between the two types of energy. Because the substances in question have been anecdotally associated with improvements in both physical and mental performance, their effects on both functions will be discussed, but with an emphasis placed on cognitive function and mood. Of the three substances discussed, caffeine's effects on cognitive and physical function, mood, and energy are best understood. It is clear that this food/drug enhances these functions when administered in moderate doses. Ephedrine may also enhance certain physical and mental functions related to "energy," but the evidence that ginseng has such properties is exceedingly weak.

Caffeine dose effect on activation-induced BOLD and CBF responses

Caffeine is a popular psychostimulant, typically found in beverages. While low to intermediate doses of caffeine are associated with positive feelings and increased mental performance and alertness, high doses induce negative feelings such as insomnia, anxiety and nervousness. We investigate if this nonlinear dose-response is present for caffeine's effects on functional activation. Twenty-seven healthy subjects were assigned randomly to four different groups: saline, 1 mg/kg, 2.5 mg/kg and 5 mg/kg doses of caffeine. Simultaneous ASL/BOLD timeseries were collected both before and after an intravenous infusion of saline or caffeine and the task-induced CBF and BOLD percent changes were compared. The maximum increase in BOLD response was associated with the intermediate caffeine dose of 2.5 mg/kg, which increased BOLD response by 32.2% and 32.5% in motor and visual areas respectively. The maximum increase in CBF response was associated with the highest caffeine dose of 5 mg/kg. This difference could be related to a different density of A(1) and A(2A) adenosine receptors in the brain.

Short-term clarithromycin administration impairs clearance and enhances pharmacodynamic effects of trazodone but not of zolpidem

The kinetic and dynamic interactions of 5 mg zolpidem and 50 mg trazodone with 500 mg clarithromycin (4 doses given over 32 h) were investigated in a 5-way double crossover study with 10 healthy volunteers. The five treatment conditions were: placebo + placebo; zolpidem + placebo; zolpidem + clarithromycin; trazodone + placebo; and trazodone + clarithromycin. Coadministration of clarithromycin increased trazodone area under the curve, prolonged elimination half-life, increased peak plasma concentration (C(max)), and reduced oral clearance. In contrast, clarithromycin had no significant effect on any kinetic parameter for zolpidem. Clarithromycin did not potentiate sedation caused by zolpidem. However, clarithromycin coadministered with trazodone significantly increased self- and observer-rated sedation and ratings of feeling "spacey." Thus, short-term clarithromycin coadministration significantly impairs trazodone clearance, elevates plasma concentrations, and enhances sedative effects. However, clarithromycin has no significant kinetic or dynamic interaction with zolpidem.