Evaluation of the central effects of alcohol and caffeine interaction

Escalating caffeine dose-dependently increases alcohol consumption in adult male, but not female, C57BL/6J mice

Although previous research has illustrated the effects of the consumption of alcohol and caffeine individually, less research has focused on the popular combination of the two drugs. The increase in alcohol consumption when combined with caffeine has led to the idea that the stimulant effects of caffeine may mask the depressant effects of alcohol, and this may contribute to increased binge drinking as the individual feels more awake and stimulated. Preclinical research has shown various effects of combined alcohol and caffeine where several studies show decreased alcohol consumption and others show increased alcohol consumption and even binge-like drinking. Results from a previous study in our lab indicate that intermittent access (IA) to steady levels of low (0.015 %) but not moderate (0.03 %) caffeine increased alcohol consumption in male C57BL/6J mice. The current studies further investigated the sex and dose differences in adult mice receiving varying concentrations of caffeine on combined alcohol intake. In Experiment 1, adult mice (n = 50, 25 males and 25 females) had IA to one of the following experimental bottles throughout the 4 week period: water, alcohol (10 % v/v), caffeine (0.015 % w/v), or 10 % alcohol +0.015 % caffeine. In Experiment 2, adult mice (n = 70, 35 males and 35 females) were given IA to one of the following experimental bottles: water, alcohol (10 % v/v; steady, maintained throughout the 4 weeks), caffeine (increasing 0.01 % to 0.015 % to 0.02 % to 0.03 % weekly), or 10 % alcohol+increasing caffeine (at the previously mentioned concentrations). When both caffeine and alcohol concentrations remained steady throughout the 4 weeks, there was no change in alcohol consumption. Chronic exposure to IA caffeine led to increased locomotor activity and decreased freezing episodes when tested in the open field test approximately 6 h after removal of the bottles. In Experiment 2, caffeine dose-dependently increased alcohol co-consumption in male mice whereas female mice consumed less alcohol when it was presented in conjunction with caffeine. The results in males are in line with clinical literature suggesting that the combination of alcohol and caffeine may lead to increased stimulation and alcohol drinking. Additionally, these studies provide evidence that the escalation of caffeine is crucial when investigating alcohol and caffeine co-consumption using the IA paradigm.

Is the prolongation latency of visual evoked potentials a pathological sign in children with Down’s syndrome without ocular abnormalities? Case–control study of children with Down’s syndrome

Objective

To evaluate retino-cortical function in children with Down’s syndrome (DS) and no evident ocular abnormalities beyond mild refractive error, by recording visual evoked potentials (VEP) in response to pattern-reversal stimuli and comparing to those of age-matched healthy controls.

Methods and analysis

All the children with DS registered at Split-Dalmatia County who met inclusion criteria of no ocular abnormalities and with refraction error between −0.5 and +2.0 D, and their age-matched healthy controls were included in the study (n=36 children, N=72 eyes, for both groups, respectively, with the same age of 9±2 years). Transient VEP was recorded and the waves with a positive peak as a response to a pattern-reversal stimulus, were analysed. The peak P100 latency, defined as the time from the stimulus onset to the main positive peak, and peak to peak amplitudes were measured.

Results

While P100 wave amplitudes were comparable between two groups (p=0.804), P100 latencies were from 4.3 to 28.5 ms longer in children with DS (p<0.001). Interocular latency difference between a VEP dominant and an inferior eye was pronounced in healthy (1.2 ms (0.2–4.0), but was almost diminished in children with DS (0.3 ms (0.1–0.5), p<0.001).

Conclusion

Our study has demonstrated that VEP response is divergent in children with DS compared with their age-matched healthy controls, indicating possible structural or functional abnormalities of the visual cortex. As VEP results are helpful in the diagnosis and treatment planning of vision-related disorders, we should reconsider the use of common VEP diagnostic criteria in subpopulation of children with DS.

The role of adenosine in alcohol-induced respiratory suppression

Alcohol-related poisoning is the foremost cause of death resulting from excessive acute alcohol consumption. Respiratory failure is crucial to the pathophysiology of fatal alcohol poisoning. Alcohol increases accumulation of extracellular adenosine. Adenosine suppresses breathing. The goal of this investigation was to test the hypothesis that adenosine signaling contributes to alcohol-induced respiratory suppression. In the first experiment, the breathing of mice was monitored following an injection of the non-selective adenosine receptor antagonist caffeine (40 mg/kg), alcohol (5 g/kg), or alcohol and caffeine combined. Caffeine reduced alcohol-induced respiratory suppression suggesting that adenosine contributes to the effects of alcohol on breathing. The second experiment utilized the same experimental design, but with the blood brain barrier impermeant non-selective adenosine receptor antagonist 8-sulfophenyltheophylline (8-SPT, 60 mg/kg) instead of caffeine. 8-SPT did not reduce alcohol-induced respiratory suppression suggesting that adenosine is contributing to alcohol-induced respiratory suppression in the central nervous system. The third and fourth experiments used the same experimental design as the first, but with the selective A1 receptor antagonist DPCPX (1 mg/kg) and the selective A2A receptor antagonist istradefylline (3.3 mg/kg). Istradefylline, but not DPCPX, reduced alcohol-induced respiratory suppression indicating an A2A receptor mediated effect. In the fifth experiment, alcohol-induced respiratory suppression was evaluated in Adk+/- mice which have impaired adenosine metabolism. Alcohol-induced respiratory suppression was exacerbated in Adk+/- mice. These findings indicate that adenosinergic signaling contributes to alcohol-induced respiratory suppression. Improving our understanding of how alcohol affects breathing may lead to better treatment strategies and better outcomes for patients with severe alcohol poisoning.

Pharmacokinetics of Caffeine: A Systematic Analysis of Reported Data for Application in Metabolic Phenotyping and Liver Function Testing

Caffeine is by far the most ubiquitous psychostimulant worldwide found in tea, coffee, cocoa, energy drinks, and many other beverages and food. Caffeine is almost exclusively metabolized in the liver by the cytochrome P-450 enzyme system to the main product paraxanthine and the additional products theobromine and theophylline. Besides its stimulating properties, two important applications of caffeine are metabolic phenotyping of cytochrome P450 1A2 (CYP1A2) and liver function testing. An open challenge in this context is to identify underlying causes of the large inter-individual variability in caffeine pharmacokinetics. Data is urgently needed to understand and quantify confounding factors such as lifestyle (e.g., smoking), the effects of drug-caffeine interactions (e.g., medication metabolized via CYP1A2), and the effect of disease. Here we report the first integrative and systematic analysis of data on caffeine pharmacokinetics from 141 publications and provide a comprehensive high-quality data set on the pharmacokinetics of caffeine, caffeine metabolites, and their metabolic ratios in human adults. The data set is enriched by meta-data on the characteristics of studied patient cohorts and subjects (e.g., age, body weight, smoking status, health status), the applied interventions (e.g., dosing, substance, route of application), measured pharmacokinetic time-courses, and pharmacokinetic parameters (e.g., clearance, half-life, area under the curve). We demonstrate via multiple applications how the data set can be used to solidify existing knowledge and gain new insights relevant for metabolic phenotyping and liver function testing based on caffeine. Specifically, we analyzed 1) the alteration of caffeine pharmacokinetics with smoking and use of oral contraceptives; 2) drug-drug interactions with caffeine as possible confounding factors of caffeine pharmacokinetics or source of adverse effects; 3) alteration of caffeine pharmacokinetics in disease; and 4) the applicability of caffeine as a salivary test substance by comparison of plasma and saliva data. In conclusion, our data set and analyses provide important resources which could enable more accurate caffeine-based metabolic phenotyping and liver function testing.

Alcohol-medication interactions: A systematic review and meta-analysis of placebo-controlled trials

Alcohol and other xenobiotics may limit the therapeutic effects of medications. We aimed at investigating alcohol-medication interactions (AMI) after the exclusion of confounding effects related to other xenobiotics. We performed a systematic review and meta-analysis of controlled studies comparing the effects induced by alcohol versus placebo on pharmacodynamic and/or pharmacokinetic parameters of approved medications. Certainty in the evidence of AMI was assessed when at least 3 independent studies and at least 200 participants were available. We included 107 articles (3097 participants): for diazepam, cannabis, opioids, and methylphenidate, we found significant AMI and enough data to assign the certainty of evidence. Alcohol consumption significantly increases the peak plasma concentration of diazepam (low certainty; almost 290 participants), cannabis (high certainty; almost 650 participants), opioids (low certainty; 560 participants), and methylphenidate (moderate certainty; 290 participants). For most medications, we found some AMI but not enough data to assign them the certainty grades; for some medications, we found no differences between alcohol and placebo in any outcomes evaluated. Our results add further evidence for interactions between alcohol and certain medications after the exclusion of confounding effects related to other xenobiotics. Physicians should advise patients who use these specific medications to avoid alcohol consumption. Further studies with appropriate control groups, enough female participants to investigate sex differences, and elderly population are needed to expand our knowledge in this field. Short phrases suitable for indexing terms.

Effects of Mixing Energy Drinks With Alcohol on Driving-Related Skills

BACKGROUND

Energy drinks (EDs) reduce sleepiness and fatigue and improve driving performance whereas alcohol does just the opposite. Although it is a trendy combination among young people, the effects of alcohol mixed with EDs on driving performance have been poorly studied. The aim was to assess if there is an interaction between the effects of both drinks on driving-related skills as well as perceptions about driving ability.

METHODS

We conducted a randomized, double-blind, and placebo-controlled 4-way crossover clinical trial. Participants were 16 healthy volunteers. Interventions of 60 g of ethanol and 750 mL of Red Bull (RB) were administered in 2 separated doses. Conditions were alcohol + RB placebo, alcohol + RB, alcohol placebo + RB, and both placebos. Objective performance was assessed using a tracking test and simple reaction time, N-Back, and movement estimation tasks. Additionally, willingness to drive, other subjective effects, and ethanol and caffeine blood concentrations were also measured.

RESULTS

Alcohol increased the time outside the road in the tracking test and increased simple reaction time, but the addition of RB had no main or interaction effects on performance. Nonetheless, driving-related skills after alcohol + RB were better than after alcohol alone. Willingness to drive increased with the combination of drinks. RB also reduced alcohol-induced sedation whereas drunkenness did not change. These effects were seen even though alcohol + RB increased alcohol (14.8%) and caffeine plasma concentrations (17.6%).

CONCLUSIONS

Mixing EDs with alcohol predisposes consumers to drive under alcohol influence, perhaps in part because EDs counteract its detrimental effects on driving-related skills. Clinicaltrials.gov: NCT02771587.

Low but not moderate amounts of caffeine increase co-consumption of ethanol in C57BL/6J mice

The increasingly popular combination of "energy drinks" containing high amounts of caffeine and alcohol has been shown to induce a stimulated, rather than sedated, state which may result in increased binge drinking and increased risk for alcohol-attributable accidents. We sought to examine consumption patterns of and withdrawal from alcohol and caffeine using a voluntary co-consumption animal model. Male and female adult C57BL/6J mice were given access to increasing doses of caffeine (0.01-0.05%) and/or alcohol (3-20%) in a two-bottle choice, intermittent access voluntary paradigm with fluid consumption recorded daily. Anxiety-like behavior during withdrawal was assessed via elevated plus maze or open field test in experiment 2. Increasing both alcohol and caffeine simultaneously in Experiment 1 resulted in no significant changes in co-consumption compared to mice given access to only alcohol or caffeine. Experiment 2 held caffeine concentration steady while slowly increasing alcohol content and resulted in mice consuming more alcohol when it was consumed in tandem with low dose caffeine. Both male and female mice consumed more caffeine when it was paired with alcohol; however, no significant differences were observed during withdrawal behavior. These results suggest that caffeine may dose-dependently positively influence alcohol consumption in mice and echo clinical literature suggesting that caffeine and alcohol together may result in a heightened state of stimulation and lead to further binge drinking. The intermittent access paradigm affords increased translational validity regarding investigations of alcohol and caffeine co-consumption and may be useful in identifying the neurobiological mechanisms concerning co-consumption of such substances.

Rewarding and aversive doses of caffeine alter activity but not conditioned place preference induced by ethanol in DBA/2J mice

Increases in the consumption of ethanol and caffeine have been attributed to increased subjective feelings of intoxication and pleasure from the combination. Previous studies have shown that caffeine can be rewarding at low doses and aversive at high doses, although these findings are at times inconsistent between studies using comparable doses. Similarly, studies investigating the rewarding effects of ethanol and caffeine combinations have yielded mixed results. To address this issue, the present experiments were designed to investigate the rewarding effects of caffeine, as well as of caffeine + ethanol combinations. Male DBA/2J mice were exposed to an unbiased conditioned place preference (CPP) procedure with various doses of caffeine (1, 3, 10, 30 mg/kg) and ethanol (1, 2 g/kg), as well as various conditioning trial durations (5, 30, 60 min). Caffeine dose-dependently increased locomotor activity during conditioning, and produced a biphasic effect on place conditioning. Specifically, a low dose of caffeine (3 mg/kg) produced place preference, while a high dose (30 mg/kg) produced place aversion. When combined with alcohol, caffeine dose-dependently increased ethanol's stimulatory effect. However, the addition of caffeine had no effect on ethanol place preference, as there were no differences in the strength of place preference between mice conditioned with ethanol alone, and mice conditioned with any combination of ethanol and caffeine. These studies add evidence for caffeine's biphasic effects while also emphasizing the importance of considering temporal and methodological parameters when using Pavlovian conditioning procedures to study drug combinations.

Impact of Spectral Severity of Alcoholism on Visual-Evoked Potentials: A Neuropsychiatric Perspective

Background:

The deleterious effects of alcohol on the brain are replete in literature. Only a few neurophysiologic measures can pick up the neuronal dysfunctions, one of them being visual-evoked potential (VEP). A very limited amount of data exists on the progression of neural abnormalities related to the spectral severity of alcoholism.

Aim of the Study:

To evaluate the impact of spectral severity of alcoholism through VEP and to understand the emergence of any specific pattern or morphometric abnormalities related to alcohol-induced neuropsychiatric presentations.

Methodology:

A total of 90 cases were recruited in addition to 180 age- and sex-matched controls using purposive and random sampling. The Structured Clinical Interview for DSM-IV Axis I Disorders, Clinician Version and Campbell Neuropsychiatric Inventory were used to evaluate alcohol disorders and its neuropsychiatric complications apart from the mandatory consultant-specific clinical evaluations of all the cases. Of 90 cases of alcohol dependence, 15 patients were currently abstinent for >6 months, 15 had alcohol intoxication, 15 had signs of alcohol withdrawal, 15 had physical complications, 15 had psychiatric comorbidity, and 15 had neurological complications such as epilepsy. VEP recordings were taken using an Evoked Potential Recorder (RMS EMG. EP MARK II) where the stimulus configuration consisted of transient pattern-reversal method in which a black and white checkerboard was generated full field.

Results:

Mean age of cases was 37.71 ± 11.49 years compared to 39.43 ± 10.67 years in controls (range 18–65 years). VEP abnormalities comprising of prolonged latencies (62.5%) with a statistically significant difference (P < 0.001) from the healthy controls was observed in cases of alcohol withdrawal syndrome. Predominant amplitude reduction with normal latency was obtained in 37.5% cases of withdrawal. Severe VEP abnormalities, i.e., both latency delay and amplitude reduction, were found in 75% patients with psychiatric comorbidity, 66.67% patients with neurological complications, i.e., epilepsy, and 33.34% patients with physical complications. An explicit finding of prominent interocular differences was a prominent feature present in 25% of patients with complications.

Acute effect of caffeine on pattern-reversal visual evoked potential: a randomized-controlled study

Purpose: This study was aimed to investigate the acute effect of caffeine intake on pattern-reversal (PR) visual evoked potential (VEP). Methods: This randomized controlled study included 40 participants who were divided into two groups randomly (group 1 [study group, n = 20] and group 2 [control group, n = 20]). While the study group received coffee beverages made from 6 g pure coffee beans (36 mg of caffeine per gram) containing approximately 216 mg caffeine, the control group was given beverages containing 200 mg lactose without caffeine. PR-VEP test was performed at baseline and 1 h after the beverage intake. The right eyes of both groups were used for the statistical analysis. Results: The median age of group 1 (8 male and 12 female) and group 2 (7 male and 13 female) were 31.0 (range, 21-59) and 36.5 (range, 20-59) years, respectively. No statistically significant difference was found between two groups in terms of age (p = 0.398) and gender (p = 0.744). Before the caffeine intake, median P100 latency and amplitudes were 109.90 ms (range: 99.60-120.60) and 12.45 µV (range: 5.20-19.30), respectively. One hour after caffeine intake, corresponding values were 110.70 ms (range: 99.00-114.60) and 12.45 µV (range: 5.70-20.0). Baseline P100 latency and amplitude values were not significantly different from the values recorded 1 h after caffeine intake (p > 0.05). Conclusions: This study showed that ingesting moderate amounts of caffeine did not affect PR-VEP parameters. Therefore, caffeine restriction does not seem to be required before the PR-VEP test. Further studies are needed to confirm our findings.

Attentional and working memory performance following alcohol and energy drink: A randomised, double-blind, placebo-controlled, factorial design laboratory study

Alcohol mixed with energy drinks (AMED) studies have typically not shown antagonism of acute alcohol effects by energy drink (ED), particularly over relatively short time frames. This study investigated the effects of alcohol, ED, and AMED on attentional and working memory processes over a 3 h period. Twenty-four young adults took part in a randomised, double-blind, placebo-controlled, factorial, 4-arm study. They were administered 0.6g/kg alcohol and 250 ml ED (containing 80 mg caffeine), and matching placebos alone and in combination. A battery of attentional and working memory measures was completed at baseline then 45, 90 and 180 min post-treatment. Alcohol produced a characteristic shift in speed/accuracy trade-off, having little effect on reaction times while increasing errors on all attentional measures (4-choice Reaction Time, Number Pairs and Visual Search), as well as a composite Attentional error score and one working memory task (Serial Sevens). ED alone improved two working memory measures (Memory Scanning accuracy and Digit-Symbol reaction times) and improved speed of responding on a composite Working Memory score. There was no consistent pattern of AMED vs. alcohol effects; AMED produced more errors than alcohol alone on one attentional measure (Visual Search errors) at 45 min only whereas AMED resulted in fewer errors on the Serial Sevens task at 90 min and better Digit-Symbol accuracy and reaction time at 45 min. Alcohol consumption increases error rate across several attentional and working memory processes. Mutual antagonism between alcohol and ED showed no consistent pattern and likely reflects a complex interaction between caffeine and alcohol levels, phase of the blood alcohol limb, task domain and cognitive load.

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.

The influence of caffeine on ethyl glucuronide levels in rat serum and in rat hair

BACKGROUND

Ethanol and caffeine are the most widely used psychoactive substances in the world, with an observed steady increase in the combined consumption of alcohol and caffeine. Specific signs of ethanol-caffeine interactions have been reported both in humans and in animals. The metabolic effects of these interactions have not been fully elucidated. There are no published reports on the influence of caffeine on ethyl glucuronide (EtG) formation. EtG is a direct metabolite of ethanol and is very often used as a biomarker of alcohol consumption. Here, we investigated the influence of caffeine on the formation of EtG in rat plasma and EtG incorporation into the hair.

METHODS

Studies were conducted on three male Wistar rat groups, each receiving either ethanol at 3 g/kg/day, ethanol (at the same dose) with caffeine at 3 mg/kg/day, or caffeine at 3 mg/kg/day for four weeks. EtG and caffeine levels were evaluated in hair and in blood after the last administration.

RESULTS

Blood EtG levels after the administration of ethanol together with caffeine were significantly higher than after the administration of ethanol alone. EtG levels in rat hair in the ethanol-and-caffeine group were also higher than in the ethanol-only group, but the difference was not statistically significant.

CONCLUSION

This study shows the possible effect of ethanol and caffeine co-administration on EtG formation. Caffeine stimulates EtG synthesis resulting in increased blood and, possibly, hair levels of this metabolite. However, the role of these changes in estimating alcohol consumption requires further studies.

Interindividual Differences in Caffeine Metabolism and Factors Driving Caffeine Consumption

Most individuals adjust their caffeine intake according to the objective and subjective effects induced by the methylxanthine. However, to reach the desired effects, the quantity of caffeine consumed varies largely among individuals. It has been known for decades that the metabolism, clearance, and pharmacokinetics of caffeine is affected by many factors such as age, sex and hormones, liver disease, obesity, smoking, and diet. Caffeine also interacts with many medications. All these factors will be reviewed in the present document and discussed in light of the most recent data concerning the genetic variability affecting caffeine levels and effects at the pharmacokinetic and pharmacodynamic levels that both critically drive the level of caffeine consumption. The pharmacokinetics of caffeine are highly variable among individuals due to a polymorphism at the level of the CYP1A2 isoform of cytochrome P450, which metabolizes 95% of the caffeine ingested. Moreover there is a polymorphism at the level of another critical enzyme, N-acetyltransferase 2. At the pharmacodynamic level, there are several polymorphisms at the main brain target of caffeine, the adenosine A2A receptor or ADORA2. Genetic studies, including genome-wide association studies, identified several loci critically involved in caffeine consumption and its consequences on sleep, anxiety, and potentially in neurodegenerative and psychiatric diseases. We start reaching a better picture on how a multiplicity of biologic mechanisms seems to drive the levels of caffeine consumption, although much more knowledge is still required to understand caffeine consumption and effects on body functions.

Adenosine A2A receptor mediates hypnotic effects of ethanol in mice

Ethanol has extensive effects on sleep and daytime alertness, causing premature disability and death. Adenosine, as a potent sleep-promoting substance, is involved in many cellular and behavioral responses to ethanol. However, the mechanisms of hypnotic effects of ethanol remain unclear. In this study, we investigated the role of adenosine in ethanol-induced sleep using C57BL/6Slac mice, adenosine A_2A receptor (A_2AR) knockout mice, and their wild-type littermates. The results showed that intraperitoneal injection of ethanol (3.0 g/kg) at 21:00 decreased the latency to non-rapid eye movement (NREM) sleep and increased the duration of NREM sleep for 5 h. Ethanol dose-dependently increased NREM sleep, which was consistent with decreases in wakefulness in C57BL/6Slac mice compared with their own control. Caffeine (5, 10, or 15 mg/kg), a nonspecific adenosine receptor antagonist, dose-dependently and at high doses completely blocked ethanol-induced NREM sleep when administered 30 min prior to (but not after) ethanol injection. Moreover, ethanol-induced NREM sleep was completely abolished in A_2AR knockout mice compared with wild-type mice. These findings strongly indicate that A_2AR is a key receptor for the hypnotic effects of ethanol, and pretreatment of caffeine might be a strategy to counter the hypnotic effects of ethanol.

The Effects of Alcohol on Visual Evoked Potential and Multifocal Electroretinography

The aim of this study was to investigate the acute effects of ethanol administration on pattern-reversal visual evoked potential (VEP) and multifocal electroretinography (mfERG). Fifteen healthy subjects with no ocular or general disease were recruited. VEP (0.25° pattern sizes) and mfERG with 19 elements in two recording segments were performed before ethanol administration to obtain baseline for each participant. A few days later, the participants visited again for VEP and mfERG measurements after ethanol administration. Ethanol (0.75 g/kg) was administered orally over the course of 30 minutes. VEP and blood alcohol concentration were evaluated one hour after ethanol administration, and mfERG was conducted after pupil dilation. The Wilcoxon signed-rank test was used to compare parameter changes after randomized eye selection. The mean blood alcohol concentration was 0.034% ± 0.05% by volume. VEP revealed a P100 latency delay (109.4 ± 5.3; 113.1 ± 8.2; P = 0.008) after alcohol administration. The P1 implicit time of ring 1 on mfERG showed a trend of shortening after alcohol administration (37.9 ± 1.0; 37.2 ± 1.5; P = 0.048). However, the changes did not show statistical significance after Bonferroni correction. In conclusion, orally administrated ethanol (0.75 g/kg) appears to suppress the central nervous system, but it is not clear whether alcohol intake affects the retina.

The effects of alcohol mixed with energy drink (AMED) on subjective intoxication and alertness: results from a double-blind placebo-controlled clinical trial

OBJECTIVE

The purpose of this double blind placebo controlled study was to examine if specific effects on subjective intoxication and alertness-sleepiness ratings could be demonstrated after consuming alcohol mixed with energy drink (AMED) when compared to consuming alcohol only (AO).

METHODS

56 healthy volunteers rated their subjective intoxication on a scale ranging from 0 (sober) to 10 (highly intoxicated) at baseline, breath alcohol concentration (BAC) of 0%, and at BAC 0.08%, 0.05%, and 0.02%. Alertness-sleepiness was assessed with the Karolinska sleepiness scale. Scores of the AMED and AO condition, at each BAC level, were compared.

RESULTS

Subjective intoxication for AMED and AO did not differ significantly from each other at any BAC level, except for BAC 0.02%. A significant increase in sleepiness scores was found in the AO condition, whereas scores remained stable in the AMED condition. Sleepiness scores at BAC0.08% and 0.05% were significantly lower after AMED when compared to AO. However, the observed differences between AMED and AO were small and have no clinical relevance.

CONCLUSION

Mixing alcohol with energy drink had no overall masking effect on subjective intoxication caused by alcohol, nor had a relevant effect on subjective alertness-sleepiness ratings. Copyright © 2016 John Wiley & Sons, Ltd.

The Four-Loko Effect

There have been recent reports of mass hospitalizations for alcohol intoxication following consumption of fruit-flavored, caffeinated, alcoholic drinks-especially concerning one brand in particular: Four Loko. Caffeine was quickly determined to be the culprit. In accordance with a directive by the Food and Drug Administration, caffeine was removed from Four Loko and similar beverages. However, the evidence that caffeine played a prominent role in widespread displays of intoxication is far from clear. Rather, it is likely that Four Loko-type drinks are especially effective as intoxicants because they provide alcohol in an unusual context. It has been known for many years that drug tolerance partially results from an association between drug-paired stimuli and the drug effect. When these stimuli are altered, the drug-experienced individual does not display the expected tolerant response to the drug-rather, an enhanced (i.e., nontolerant) response is seen. Four Loko and similar beverages may be especially effective intoxicants because they provide a very novel flavor context for alcohol. A recent announcement by the manufacturer of Four Loko suggests (either by design or happenstance) appreciation of the contribution of alcohol-associated cues to alcohol tolerance.

A comprehensive review of the effects of mixing caffeinated energy drinks with alcohol

BACKGROUND

In response to concern about whether mixing caffeinated energy drinks with alcohol (AED) increases alcohol consumption and related harm, and the role of industry in this debate, we conducted a comprehensive review of the research evidence on the effects of AED and documented industry involvement in this research.

METHOD

A systematic review of 6 databases. Studies must have examined the effect of consuming alcohol with energy drinks (ED) or caffeine on alcohol-related outcomes.

RESULTS

62 studies were identified; 29 were experiments, 9 had industry ties (8 with Red Bull GmbH). Young adults who consumed AED drank more alcohol and experienced more alcohol-related harm than other drinkers. There was insufficient evidence to conclude that AED led to increased alcohol consumption or altered the nature of alcohol-related harm. However, AED consumers reported that AED increased stimulation and alertness, offset fatigue from drinking, and facilitated drinking. Experimental research also found that combining ED or caffeine with alcohol increased stimulation and alertness, offset alcohol-related fatigue and increased the desire to keep drinking. It did not change BAC, perceived intoxication, perceived impairment and it did not reverse alcohol-induced impairment on simple psychomotor tasks. Combining ED/caffeine with alcohol reduced alcohol-induced impairment on some but not all aspects of complex tasks. Although few in number, studies with industry ties presented contrary evidence.

CONCLUSION

A growing body of evidence suggests that AED may facilitate drinking and related harms via its effects on intoxication but a causal link needs to be confirmed. The influence of industry involvement in this area of research needs to be monitored.

Effects of mixing alcohol with energy drink on objective and subjective intoxication: results from a Dutch on-premise study

BACKGROUND

The purpose of this on-premise study was to determine if alcohol mixed with energy drink (AMED) consumption masks the subjective feelings of intoxication when compared to consuming alcohol only.

METHODS

The study was conducted on five nights in the city center of Utrecht. N = 997 people leaving bars were interviewed about their alcohol consumption with and without energy drinks, for that particular evening and for other occasions. People reporting drug and medication use were excluded (N = 84). Subjective intoxication was rated on a 10-point scale. Objective intoxication (breath alcohol concentration, BrAC) was determined with a breath alcohol test. Three groups were identified: (1) the AMED-tonight group (N = 185, 20.2 %), (2) the AMED-other-nights group (N = 246, 27.1 %), and (3) the no-AMED group (N = 482, 52.7 %).

RESULTS

Objective intoxication (BrAC) did not significantly differ (p = 0.94) between the AMED-tonight group (0.074 % ± 0.05), AMED-other-nights group (0.073 % ± 0.05), and the no-AMED group (0.074 % ± 0.05). In line, subjective intoxication was not significantly different (p = 0.96) between the AMED-tonight group (4.5 ± 2.2), AMED-other-nights group (4.6 ± 2.3), and no-AMED group (4.6 ± 2.2). Within-subjects comparisons revealed no significant differences in total alcohol consumption between AMED occasions and alcohol only occasions. Regression analyses showed that "gender" (beta = 0.078, p = 0.016), "time of testing" (beta = 0.085, p = 0.009,) and "BrAC" (beta = 0.574, p = 0.0001) together explained 37.7 % of variance of subjective intoxication scores (Cohen's f (2) = 0.605). Whether or not subjects consumed energy drinks did not predict subjective intoxication scores.

CONCLUSION

The data suggests that mixing alcohol with energy drink does not mask subjective intoxication.

Effects of mixing alcohol with caffeinated beverages on subjective intoxication: a systematic review and meta-analysis

It has been suggested that mixing alcohol with energy drinks or other caffeinated beverages may alter the awareness of (or 'mask') intoxication. The proposed reduction in subjective intoxication may have serious consequences by increasing the likelihood of engaging in potentially dangerous activities while intoxicated. A literature search was conducted to collect all studies measuring subjective intoxication after administration of alcohol with energy drinks, or with other caffeinated alcoholic drinks compared with alcohol alone. The studies were critically reviewed and, where possible, included in a meta-analysis in order to determine whether masking exists after mixing alcohol with caffeinated beverages. Sixteen articles were identified, of which nine could be used for the meta-analysis. When including the higher caffeine dose studies, the meta-analysis revealed no significant masking effect (p=0.404). Similarly, when including the lower caffeine dose studies, no significant masking effect was found (p=0.406). Despite the large range of caffeine doses (2.0-5.5 mg/kg resulting in absolute levels of 46-383 mg) and alcohol levels 0.29-1.068 g/kg (resulting in blood alcohol concentration (BAC) from 0.032 to 0.12%) investigated, caffeine had no effect on the judgement of subjective intoxication.

Effects of alcohol and energy drink on mood and subjective intoxication: a double-blind, placebo-controlled, crossover study

OBJECTIVE

There is concern that combining energy drinks with alcohol may 'mask' subjective intoxication leading to greater alcohol consumption. This study examines the effects of alcohol alone and combined with energy drink on objective and subjective intoxication and mood over the course of 3 h.

METHOD

Using a double-blind, placebo-controlled, balanced, crossover design, 24 participants (mean age 22.23 years) were administered with double placebo, 0.6 g/kg alcohol (mean peak blood alcohol content of 0.051%), 250 ml energy drink and alcohol/energy drink, according to a Latin square design, with a washout of >48 h. On each visit, they were breathalysed and rated themselves on a comprehensive battery of mood items at baseline and then at 45, 90 and 180 min post-drink.

RESULTS

Blood alcohol and subjective intoxication were significantly increased following both alcohol alone and alcohol/energy drink. Both measures were statistically indistinguishable between alcohol conditions. In keeping with its (80 mg) caffeine content, the energy drink alone significantly increased self-rated 'alertness' and reduced 'depression-dejection' scores compared with the combined alcohol/energy drink. The alcohol/energy drink increased 'vigor' and 'contentment' at 45 min and decreased 'contentment' at 180 min.

CONCLUSIONS

The co-ingestion of an energy drink with alcohol does not differently influence blood alcohol content recordings or subjective intoxication compared with alcohol alone, although some mood items are differentially affected.

"Wired," yet intoxicated: modeling binge caffeine and alcohol co-consumption in the mouse

BACKGROUND

The combination of highly caffeinated "energy drinks" with alcohol (ethanol [EtOH]) has become popular among young adults and intoxication via such beverages has been associated with an elevated risk for harmful behaviors. However, there are discrepancies in the human literature regarding the effect of caffeine on alcohol intoxication, perhaps due to confounding factors such as personality type, expectancy, and history of exposure. Animal models of co-exposure are resistant to such issues; however, the consequences of voluntary co-consumption have been largely ignored in the animal literature. The primary goal of this work was to characterize a mouse model of binge caffeine and EtOH co-consumption employing the limited access "Drinking-in-the-Dark" (DID) paradigm.

METHODS

Caffeine was added to a 20% alcohol solution via DID. Alcohol/caffeine intake, locomotor behavior, ataxia, anxiety-like behavior, and cognitive function were evaluated as a consequence of co-consumption in adult male C57BL/6J mice.

RESULTS

Caffeine did not substantially alter binge alcohol intake or resultant blood EtOH concentrations (BECs), nor did it alter alcohol's anxiolytic effects on the elevated plus maze or cognitive-interfering effects in a novel object-recognition task. However, no evidence of alcohol-induced sedation was observed in co-consumption groups that instead demonstrated a highly stimulated state similar to that of caffeine alone. The addition of caffeine was also found to mitigate alcohol-induced ataxia.

CONCLUSIONS

Taken together, our mouse model indicates that binge co-consumption of caffeine and alcohol produces a stimulated, less ataxic and anxious, as well as cognitively altered state; a state that could be of great public health concern. These results appear to resemble the colloquially identified "wide awake drunk" state that individuals seek via consumption of such beverages. This self-administration model therefore offers the capacity for translationally valid explorations of the neurobiological consequences of binge co-consumption to assess the public health risk of this drug combination.

Psychomotor and subjective effects of bilastine, hydroxyzine, and cetirizine, in combination with alcohol: a randomized, double-blind, crossover, and positive-controlled and placebo-controlled Phase I clinical trials

OBJECTIVE

The aim of this study was to compare the effects of concomitant administration of alcohol and bilastine versus alcohol alone on the central nervous system.

METHODS

Twenty-four healthy young volunteers of both sexes participated in a randomized, double-blind, double-dummy, crossover, and positive-controlled and placebo-controlled clinical trials. At 1-week intervals, subjects received six different treatments: (i) placebo; (ii) alcohol 0.8 g/kg alone (ALC); (iii) ALC in combination with: bilastine 20 mg (B20 + A); (iv) bilastine 80 mg (B80 + A); (v) cetirizine 10 mg (CET + A); and (vi) hydroxyzine 25 mg (HYD + A). Psychomotor performance tests (fine motor, finger tapping, nystagmus, critical flicker-fusion frequency, temporal estimation, 'd2' cancellation, and simple reaction time) and subjective self-reports (drunkenness, drowsiness, mental slowness, clumsiness, anger, attentiveness, competence, happiness, hostility, interest, and extroversion) were carried out at baseline and multiple points thereafter.

RESULTS

All active treatments induced a significant psychomotor impairment. The greatest and most lasting impairment was observed with HYD + A followed by B80 + A and CET + A. In contrast, objective measures showed less impairment with B20 + A and ALC, both with a similar magnitude. Self-reports showed a subjective perception of performance impairment in all active treatments.

CONCLUSION

Concomitant administration of bilastine (at therapeutic dose) and alcohol does not produce greater central nervous system depressant effects than ACL alone.

The effects of caffeine, nicotine, ethanol, and tetrahydrocannabinol on exercise performance

Caffeine, nicotine, ethanol and tetrahydrocannabinol (THC) are among the most prevalent and culturally accepted drugs in western society. For example, in Europe and North America up to 90% of the adult population drinks coffee daily and, although less prevalent, the other drugs are also used extensively by the population. Smoked tobacco, excessive alcohol consumption and marijuana (cannabis) smoking are addictive and exhibit adverse health effects. These drugs are not only common in the general population, but have also made their way into elite sports because of their purported performance-altering potential. Only one of the drugs (i.e., caffeine) has enough scientific evidence indicating an ergogenic effect. There is some preliminary evidence for nicotine as an ergogenic aid, but further study is required; cannabis and alcohol can exhibit ergogenic potential under specific circumstances but are in general believed to be ergolytic for sports performance. These drugs are currently (THC, ethanol) or have been (caffeine) on the prohibited list of the World Anti-Doping Agency or are being monitored (nicotine) due to their potential ergogenic or ergolytic effects. The aim of this brief review is to evaluate the effects of caffeine, nicotine, ethanol and THC by: 1) examining evidence supporting the ergogenic or ergolytic effects; 2) providing an overview of the mechanism(s) of action and physiological effects; and 3) where appropriate, reviewing their impact as performance-altering aids used in recreational and elite sports.

Effects of alcohol mixed with energy drink and alcohol alone on subjective intoxication

Recent studies suggest that the combination of caffeine-containing drinks together with alcohol might reduce the subjective feelings of alcohol intoxication—the so-called “masking effect”. In this study, we aimed to review the effects of alcohol in combination with caffeine or energy drink with special focus on the “masking effect”. Fifty-two healthy male volunteers were analysed concerning breath alcohol concentration and subjective sensations of intoxication using a 18 item Visual Analogue Scale in a randomised, double-blinded, controlled, four treatments cross-over trial after consumption of (A) placebo, (B) alcohol (vodka 37.5 % at a dose of 46.5 g ethanol), (C) alcohol in combination with caffeine at a dose of 80 mg (equivalent to one 250 ml can of energy drink) and (D) alcohol in combination with energy drink at a dose of 250 ml (one can). Primary variables were headache, weakness, salivation and motor coordination. Out of four primary variables, weakness and motor coordination showed a statistically significant difference between alcohol and non-alcohol group, out of 14 secondary variables, five more variables (dizziness, alterations in sight, alterations in walking, agitation and alterations in speech) also showed significant differences due mainly to contrasts with the non-alcohol group. In none of these end points, could a statistically significant effect be found for the additional ingestion of energy drink or caffeine on the subjective feelings of alcohol intoxication. This within-subjects study does not confirm the presence of a “masking effect” when combining caffeine or energy drink with alcohol.

Expression of behavioral sensitization to ethanol is increased by energy drink administration

Alcohol abuse and dependence are important medical, social and economical problems, affecting millions of people. A relatively recent habit among young people is mixing alcohol with energy drinks (ED), in spite of the risks involved may be higher than those associated with alcohol consumption alone. The mixture of alcohol and energy drinks, both with stimulant properties, may alter the perception of intoxication and could lead individuals to believe they are less drunk and can drink more or for longer periods of time. In animals, the repeated administration of ethanol can lead to a progressive increase of the locomotor stimulant effect, known as behavioral sensitization, a drug-dependent behavioral plasticity associated with vulnerability to addiction. As well as for addiction, there are clear individual differences in the level of sensitization to ethanol among species and even among individuals from the same strain. The present study assessed how ED affects the expression of ethanol sensitization. Female mice chronically treated with ethanol (2.4 g/kg) were classified as low-sensitized or high-sensitized. Two days later, different groups of mice were submitted to saline+water, ethanol+water or ethanol+ED systemic challenges. As expected, only the high-sensitized group expressed clear sensitization after ethanol administration. However, the administration of ethanol+ED triggered the sensitization expression in the low-sensitized group. These data indicate that the combined use of ED and ethanol can potentiate the stimulant and, consequently, the reward effects of ethanol in previously treated mice. If a similar process occurs in human beings, the use of ED can increase the risk of developing alcohol abuse or dependence.

The combined effects of alcohol, caffeine, and expectancies on subjective experience, impulsivity, and risk-taking

Caffeinated alcoholic beverage (CAB) consumption is a rapidly growing phenomenon among young adults and is associated with a variety of health-risk behaviors. The current study examined whether either caffeinated alcohol or the expectation of receiving caffeinated alcohol altered affective, cognitive, and behavioral outcomes hypothesized to contribute to risk behavior. Young adult social drinkers (N = 146) participated in a single session where they received alcohol (peak Breath Alcohol Content = .088 g/dL, SD = .019; equivalent to about four standard drinks) and were randomly assigned to one of four further conditions: 1) no caffeine, no caffeine expectancy, 2) caffeine and caffeine expectancy, 3) no caffeine but caffeine expectancy, 4) caffeine but no caffeine expectancy. Participants' habitual CAB consumption was positively correlated with measures of impulsivity and risky behavior, independently of study drugs. Administration of caffeine (mean dose = 220 mg, SD = 38; equivalent to about 2.75 Red Bulls) in the study reduced subjective ratings of intoxication and reversed the decrease in desire to continue drinking, regardless of expectancy. Caffeine also reduced the effect of alcohol on inhibitory reaction time (RT) (faster incorrect responses). Participants not expecting caffeine were less attentive after alcohol, whereas participants expecting caffeine were not, regardless of caffeine administration. Alcohol decreased response accuracy in all participants except those who both expected and received caffeine. Findings suggest that CABs may elevate risk for continued drinking by reducing perceived intoxication, and by maintaining the desire to continue drinking. Simply expecting to consume caffeine may reduce the effects of alcohol on inattention, and either expecting or consuming caffeine may protect against other alcohol-related performance decrements. Caffeine, when combined with alcohol, has both beneficial and detrimental effects on mechanisms known to contribute to risky behavior.

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.

The effects of energy drink in combination with alcohol on performance and subjective awareness

RATIONALE

This study investigated the coadministration of an energy drink with alcohol to study the effects on subjective intoxication and objective performance.

OBJECTIVES

This study aims to evaluate the objective and subjective effects of alcohol versus placebo at two alcohol doses, alone and in combination with an energy drink, in a balanced order, placebo-controlled, double-blind design.

METHODS

Two groups of ten healthy volunteers, mean (SD) age of 24 (6.5), participated in the study. One group consumed energy drink containing 80 mg of caffeine and the other consumed a placebo drink, with both receiving two alcohol doses (0.046 and 0.087% breathalyser alcohol concentration). Tests included breath alcohol assessment, objective measures of performance (reaction time, word memory and Stroop task) and subjective visual analogue mood scales.

RESULTS

Participants showed significantly impaired reaction time and memory after alcohol compared to the no alcohol condition and had poorer memory after the higher alcohol dose. Stroop performance was improved with the energy drink plus alcohol combination compared to the placebo drink plus alcohol combination. Participants felt significant subjective dose-related impairment after alcohol compared to no alcohol. Neither breath alcohol concentration nor the subjective measures showed a significant difference between the energy drink and the placebo energy drink when combined with alcohol.

CONCLUSIONS

Subjective effects reflected awareness of alcohol intoxication and sensitivity to increasing alcohol dose. There were no overall significant group differences for subjective measures between energy drink and placebo groups in the presence of alcohol and no evidence that the energy drink masked the subjective effects of alcohol at either dose.

Separating neural and vascular effects of caffeine using simultaneous EEG-FMRI: differential effects of caffeine on cognitive and sensorimotor brain responses

The effects of caffeine are mediated through its non-selective antagonistic effects on adenosine A(1) and A(2A) adenosine receptors resulting in increased neuronal activity but also vasoconstriction in the brain. Caffeine, therefore, can modify BOLD FMRI signal responses through both its neural and its vascular effects depending on receptor distributions in different brain regions. In this study we aim to distinguish neural and vascular influences of a single dose of caffeine in measurements of task-related brain activity using simultaneous EEG-FMRI. We chose to compare low-level visual and motor (paced finger tapping) tasks with a cognitive (auditory oddball) task, with the expectation that caffeine would differentially affect brain responses in relation to these tasks. To avoid the influence of chronic caffeine intake, we examined the effect of 250 mg of oral caffeine on 14 non and infrequent caffeine consumers in a double-blind placebo-controlled cross-over study. Our results show that the task-related BOLD signal change in visual and primary motor cortex was significantly reduced by caffeine, while the amplitude and latency of visual evoked potentials over occipital cortex remained unaltered. However, during the auditory oddball task (target versus non-target stimuli) caffeine significantly increased the BOLD signal in frontal cortex. Correspondingly, there was also a significant effect of caffeine in reducing the target evoked response potential (P300) latency in the oddball task and this was associated with a positive potential over frontal cortex. Behavioural data showed that caffeine also improved performance in the oddball task with a significantly reduced number of missed responses. Our results are consistent with earlier studies demonstrating altered flow-metabolism coupling after caffeine administration in the context of our observation of a generalised caffeine-induced reduction in cerebral blood flow demonstrated by arterial spin labelling (19% reduction over grey matter). We were able to identify vascular effects and hence altered neurovascular coupling through the alteration of low-level task FMRI responses in the face of a preserved visual evoked potential. However, our data also suggest a cognitive effect of caffeine through its positive effect on the frontal BOLD signal consistent with the shortening of oddball EEG response latency. The combined use of EEG-FMRI is a promising methodology for investigating alterations in brain function in drug and disease studies where neurovascular coupling may be altered on a regional basis.

Effects of caffeine on alcohol-related changes in behavioural control and perceived intoxication in light caffeine consumers

RATIONALE

Caffeinated alcoholic beverages have been associated with increased risk of alcohol-related harms. However, few studies have examined these combined effects on behavioural control, which is believed to underlie many of the negative effects of alcohol consumption. In addition, studies have often omitted subjective measures, and none have directly assessed the role of caffeine consumer history.

OBJECTIVES

To examine the combined effects of alcohol and caffeine on measures of behavioural control and perceived intoxication in abstinent, light caffeine consumers.

METHODS

Participants (n = 28; 50% male) attended four sessions at which they consumed one of the following beverages in a randomised order: placebo, alcohol alone (0.6 g/kg), caffeine alone (2.0 mg/kg), and alcohol/caffeine. They completed measures of mood, intoxication, anxiety and alcohol craving before and after a task battery comprising measures of behavioural control and reaction time performance.

RESULTS

Caffeine attenuated alcohol-related performance deficits on stop-signal accuracy, had no effect on go-no-go performance deficits, and worsened accuracy on the Stroop task. Caffeine did not influence absolute changes in perceived intoxication but there was suggestion that caffeine may have changed the nature of intoxication with increases in stimulation.

CONCLUSIONS

Caffeine appears to have mixed effects on alcohol intoxication that are task-dependent. We found increased stimulation in the alcohol/caffeine condition, supporting the contention that caffeinated alcoholic beverages enable an individual to drink for longer. Future research should model real world drinking behaviour by examining how these effects change across multiple drink administrations.

Differential effects of moderate alcohol consumption on motion and contrast processing

Although a moderate blood alcohol concentration already affects attention, an effect on early visual processing is still questionable. Using psychophysical measures and visually evoked potentials (VEP), we examined the effects of alcohol on the processing of contrast and motion features. In our tasks, two lateralized stimuli were briefly presented, and participants had to identify either the stimulus of higher contrast or motion coherence. In the contrast task, alcohol was found to decrease the discrimination ability and induced a global attenuation of VEP amplitudes. In the motion task, discrimination was not impaired. VEP amplitudes were reduced contralateral to the target position, indicating an effect of alcohol on the deployment of visuospatial attention. In sum, our data suggest that specialized areas for motion and contrast processing within the visual cortex are differently sensitive to moderate alcohol exposure.

Alcohol and Caffeine: The Perfect Storm

Although it is widely believed that caffeine antagonizes the intoxicating effects of alcohol, the molecular mechanisms underlying their interaction are incompletely understood. It is known that both caffeine and alcohol alter adenosine neurotransmission, but the relationship is complex, and may be dose dependent. In this article, we review the available literature on combining caffeine and alcohol. Ethical constraints prohibit laboratory studies that would mimic the high levels of alcohol intoxication achieved by many young people in real-world settings, with or without the addition of caffeine. We propose a possible neurochemical mechanism for the increase in alcohol consumption and alcohol-related consequences that have been observed in persons who simultaneously consume caffeine. Caffeine is a nonselective adenosine receptor antagonist. During acute alcohol intake, caffeine antagonizes the "unwanted" effects of alcohol by blocking the adenosine A₁ receptors that mediate alcohol's somnogenic and ataxic effects. The A₁ receptor-mediated "unwanted" anxiogenic effects of caffeine may be ameliorated by alcohol-induced increase in the extracellular concentration of adenosine. Moreover, by means of interactions between adenosine A_2A and dopamine D₂ receptors, caffeine-mediated blockade of adenosine A_2A receptors can potentiate the effects of alcohol-induced dopamine release. Chronic alcohol intake decreases adenosine tone. Caffeine may provide a "treatment" for the withdrawal effects of alcohol by blocking the effects of upregulated A₁ receptors. Finally, blockade of A_2A receptors by caffeine may contribute to the reinforcing effects of alcohol.

"Vodka energy": too much for the adolescent nephron?

We report here the case of a 17-year-old boy who suffered acute renal failure after consuming 3 L of energy drink (ED) in combination with 1 L of vodka amounting to 4600 mg of taurine and 780 mg of caffeine mixed with 380 g of alcohol. The consumption of this mixture is extremely popular in adolescents, because the joint effects of caffeine and taurine reduce the effect of alcohol. Although there have been case reports of deaths linked to the consumption of EDs with and without alcohol, awareness of the possible dangers is still low. The fact that athletes and major sports events are sponsored by ED manufacturers implies that they may even be healthy and performance-enhancing.

Pharmacokinetics and metabolism of natural methylxanthines in animal and man

Caffeine, theophylline, theobromine, and paraxanthine administered to animals and humans distribute in all body fluids and cross all biological membranes. They do not accumulate in organs or tissues and are extensively metabolized by the liver, with less than 2% of caffeine administered excreted unchanged in human urine. Dose-independent and dose-dependent pharmacokinetics of caffeine and other dimethylxanthines may be observed and explained by saturation of metabolic pathways and impaired elimination due to the immaturity of hepatic enzyme and liver diseases. While gender and menstrual cycle have little effect on their elimination, decreased clearance is seen in women using oral contraceptives and during pregnancy. Obesity, physical exercise, diseases, and particularly smoking and the interactions of drugs affect their elimination owing to either stimulation or inhibition of CYP1A2. Their metabolic pathways exhibit important quantitative and qualitative differences in animal species and man. Chronic ingestion or restriction of caffeine intake in man has a small effect on their disposition, but dietary constituents, including broccoli and herbal tea, as well as alcohol were shown to modify their plasma pharmacokinetics. Using molar ratios of metabolites in plasma and/or urine, phenotyping of various enzyme activities, such as cytochrome monooxygenases, N-acetylation, 8-hydroxylation, and xanthine oxidase, has become a valuable tool to identify polymorphisms and to understand individual variations and potential associations with health risks in epidemiological surveys.

Effect of caffeine on central auditory pathways: An evoked potential study

Caffeine is consumed in various forms like tea, coffee, chocolates and colas. The present study evaluated the effect of caffeine on auditory brainstem response (ABR), mid latency response (MLR) and slow vertex response (SVR) in 40 male volunteers. The recordings were done using a computerized evoked potential recorder by 10-20 electrode placement system. The subjects consumed 3mg/kg body weight of caffeine after 12h abstinence from caffeine in any form. The data obtained revealed that latencies of waves IV and V along with I-V interpeak interval of ABR decreased significantly. This was accompanied with significant increase in amplitude of wave V. MLR latencies and latency of P1 wave of SVR was significantly decreased following caffeine ingestion. The results indicated that caffeine improves transmission in the peripheral and central brain auditory pathways.

Evaluation of the cognitive, psychomotor and pharmacokinetic profiles of rupatadine, hydroxyzine and cetirizine, in combination with alcohol, in healthy volunteers

INTRODUCTION

The Central Nervous System (CNS) impairment induced by moderate alcohol (ALC) ingestion may be enhanced if other drugs are taken simultaneously. Rupatadine (RUP) is a new H(1)-antihistamine which also inhibits platelet activating factor (PAF) release in inflammatory reactions.

OBJECTIVE

The main aim of the study was to assess the effects of ALC 0.8 g/Kg on RUP (10 mg and 20 mg) CNS effects. An evaluation of alcohol and RUP pharmacokinetics was also attained.

METHODS

Eighteen healthy young volunteers of both sexes participated in a phase I, randomised, crossover, double-blind, placebo-controlled study. At 2-week intervals they received six treatments: (a) placebo (PLA), (b) ALC alone and ALC in combination with: (c) hydroxyzine 25 mg (HYD), (d) cetirizine 10 mg (CET), (e) RUP 10 mg or (f) RUP 20 mg. At baseline and several times thereafter, seven psychomotor performance tests (finger tapping, fine motoric skills, nystagmus, temporal estimation, critical-flicker-fusion frequency, 'd2' cancellation, simple reaction) and eleven subjective self-reports (drunkenness, sleepiness, alertness, clumsiness, anger, inattentiveness, efficiency, happiness, hostility, interest and extraversion) were carried out. Two-way (treatment, time) ANOVAs for repeated measures to each variable together with a multivariate non-parametric approach were applied. Plasma concentrations of alcohol, and of RUP and its metabolites, were quantified by validated immunofluorescence and LC/MS/MS methods, respectively. Plasma-time curves for all compounds were analysed by means of model-independent methods.

RESULTS

The combination of alcohol with HYD, CET and RUP 20 mg produced more cognitive and psychomotor impairment as compared to alcohol alone, being the combination of alcohol and HYD the one which induced the greatest deterioration. The combination of alcohol and RUP 10 mg could not be differentiated from ALC alone. Subjective self-reports reflect effects on metacognition after the combination of alcohol with HYD and CET i.e. the increased objective impairment observed was not subjectively perceived by the subjects. No significant differences were obtained when comparing alcohol plasma concentrations assessed after the treatments evaluated. RUP showed a lineal kinetic relationship after 10 and 20 mg with a higher exposition to both metabolites assayed.

CONCLUSIONS

Present results showed that single oral doses of rupatadine 10 mg in combination with alcohol do not produce more cognitive and psychomotor impairment than alcohol alone. Higher doses of rupatadine, in combination with alcohol, may induce cognitive and psychomotor deterioration as hydroxyzine and cetirizine at therapeutic doses.

Dietary caffeine, performance and mood: enhancing and restorative effects after controlling for withdrawal reversal

This study aimed to determine whether sustained (i.e. dietary) use of caffeine has net effects on performance and mood compared with sustained abstinence, and whether dietary caffeine restores performance and mood adversely affected by sleep restriction. Participants (n = 96) alternated weekly between ingesting placebo and caffeine (1.75 mg/kg) three times daily for 4 consecutive weeks, while either rested or sleep restricted. Performance involved either a single task requiring sustained vigilance or a varied battery of brief psychomotor and cognitive tasks, and mood was assessed using the Profile of Mood States. Caffeine had no significant net enhancing effects for either performance or mood when participants were rested, and produced no net restorative effects when performance and mood were degraded by sleep restriction.

Effects of dietary caffeine on mood when rested and sleep restricted

Prolonged use of caffeine can lead to physical dependence evidenced by characteristic withdrawal symptoms during abstinence. Debate exists as to whether mood enhancement by caffeine represents a net effect or merely the restoration of abstinence-induced mood decrements. One aim of this study was to determine the net effects on mood of dietary caffeine compared with prolonged abstinence. In addition, the study aimed to determine whether caffeine restores mood degraded by a non-caffeine source, namely, sleep restriction. A double-blind placebo-controlled cross-over design was employed in which 48 male and female volunteers alternated weekly between ingesting placebo and caffeine (1.75 mg/kg) three times daily for 4 consecutive weeks, while being either rested or sleep restricted. Mood was assessed using a computerized version of the profile of mood states (POMS), giving scores for overall mood and six mood dimensions. Gender had small effects on mood, whereas all mood dimensions were markedly adversely affected by sleep restriction. Caffeine had no significant net enhancing effects on mood when participants were rested, and produced no net restorative effects when mood was degraded by sleep restriction. On the contrary, caffeine-induced decrements in mood were observed during both conditions of rest and sleep restriction.

Caffeine reversal of ethanol effects on the multiple sleep latency test, memory, and psychomotor performance

Caffeine has been shown to reverse some of the performance-impairing effects of ethanol. However, it is not known whether this antagonistic effect of caffeine is mediated by a reduction in sleepiness. The present study assessed physiological alertness/sleepiness, memory, and psychomotor performance following the administration of placebo, ethanol, and caffeine+ethanol combinations. A total of 13 healthy individuals (21-35 years old) underwent four conditions presented in a Latin Square Design: placebo-placebo, ethanol (0.5 g/kg)-placebo, ethanol (0.5 g/kg)-caffeine 150 mg, and ethanol (0.5 g/kg)-caffeine 300-mg. The Multiple Sleep Latency Test (MSLT), psychomotor performance battery, memory test, and mood/sleepiness questionnaires were administered following each condition. The peak breadth ethanol concentration (BrEC) was 0.043+/-0.0197% and did not differ among the three caffeine treatments. As expected, ethanol reduced mean latency on the MSLT. The lowest caffeine dose reversed this effect and the highest dose increased mean latency (greater alertness) significantly beyond placebo levels. Ethanol also impaired psychomotor performance and memory. The 300-mg caffeine dose restored performance and memory measures to placebo levels. Although visual analog ratings of dizziness were increased by ethanol, they were not diminished by either caffeine dose. In conclusion, Low-dose caffeine prevented the sleepiness and performance impairment associated with a moderate dose of ethanol. Thus, caffeine, similar to other stimulants, can reverse the physiologically sedating effects of ethanol, although other negative effects remain.

Central and peripheral effects of sustained caffeine use: tolerance is incomplete

AIMS

It is widely held that tolerance develops to the effects of sustained caffeine consumption. This study was designed to investigate the effects of chronic, staggered caffeine ingestion on the responses of an acute caffeine challenge, during -euglycaemia.

METHODS

Twelve healthy volunteers were randomized using a double-blind, cross-over design to take either 200 mg caffeine (C-replete) or placebo (C-naïve) twice daily for 1 week. Following baseline measurements being made, the responses to 200 mg caffeine (blood-pressure, middle cerebral artery velocity, mood and cognitive performance) were examined over the subsequent 120 min. Blood glucose was not allowed to fall below 4.0 mmol l-1.

RESULTS

After the caffeine challenge, middle cerebral artery blood velocity decreased in both conditions but was greater in the C-naïve condition (-8.0 [-10.0, -6.1] cm s-1 vs -4.9 [-6.8, -2.9] cm s-1 C-replete, P < 0.02). Systolic blood pressure rise was not significantly different in C-naïve, although this rise was more sustained over time (P < 0.04). Mood was adversely affected by regular caffeine consumption with tense aspect of mood significantly higher at baseline in C-replete 11.6 +/- 0.6 C-naïve vs 16.3 +/- 1.6 C-replete, P < 0.01). Cognitive performance was not affected by previous caffeine exposure.

CONCLUSIONS

Overall these results suggest that tolerance is incomplete with respect to both peripheral or central effects of caffeine.

Interactions between alcohol and caffeine in relation to psychomotor speed and accuracy

Unlike other CNS depressants, alcohol intoxication can be associated with increased error rates, coupled with unaffected (or speeded) response rates during psychomotor and cognitive processing. The present study examined whether concurrent consumption of caffeine may differentially affect these aspects of alcohol and performance.A randomised, double-blind, placebo-controlled design was utilised in which 64 healthy young volunteers received either 0.66 g/kg alcohol, caffeine (110-120 mg), both or neither. Performance was assessed using a four choice reaction time task (FCRT) with elements of repetitive (predictable) and random stimuli sequences and the digit symbol substitution task (DSST). Individuals on alcohol made significantly more errors during both fixed and random FCRT sequences, and there was evidence of weak antagonism of these effects by caffeine on the latter measure. On the DSST test of psychomotor speed, alcohol was associated with a significant slowing, the caffeine group were significantly faster and there was clear antagonism of the effects of alcohol by caffeine. These findings confirm that alcohol consumption is associated a greater number of errors and provide some evidence for task-specific antagonism of alcohol's cognitive effects by caffeine.

Caffeine antagonism of alcohol-induced driving impairment

The extent to which caffeine antagonizes alcohol-induced impairment of simulated automobile driving at the current lowest legal American limit (0.08% BrAC) was the focus of this study. Fifteen adults swallowed a capsule (0, 200, or 400 mg caffeine) then drank a beverage (0.0 or 0.6 g/kg ethanol) in a within-subject, double-blind, randomized procedure. Forty-five minutes later, participants completed a test battery of subjective effects scales, dynamic posturography, critical flicker fusion (CFF), choice reaction time (CRT), divided attention (Stroop test), and simulated driving. Alcohol alone increased ratings of 'dizzy', 'drug effect', and 'high', slowed CRT and brake latency, and increased body sway. Caffeine alone increased ratings of 'alert' and 'jittery', but did not significantly affect body sway or psychomotor performance. Both caffeine doses comparably counteracted alcohol impairment of brake latency but not CRT or body sway. Brake latency with either alcohol-caffeine combination remained significantly longer than that with placebo. Stroop and CFF performance were unaffected by any drug condition. The results suggest that caffeine may increase alertness and improve reaction time after alcohol use but will not completely counteract alcohol impairment in a driver.