Post-occlusive reactive hyperemia in habituated caffeine users: Effects of abstaining versus consuming typical doses

BACKGROUND

Post-occlusive reactive hyperemia (PORH) typically requires caffeine abstinence. For habitual users, it is unknown if abstinence affects PORH.

OBJECTIVE

Compare PORH after habitual users consume or abstain from caffeine.

METHODS

On separate visits (within-subject), PORH was measured in 30 participants without abstinence from typical caffeine doses (CAFF) and with abstinence (ABS). Measurements included baseline and peak hyperemic velocity, tissue saturation index slopes during ischemia (Slope 1) and following cuff deflation (Slope 2), resting arterial occlusion pressure (AOP), heart rate (HR), systolic (SBP), and diastolic (DBP) blood pressure. All variables were compared using Bayesian paired t-tests. BF10 = likelihood of alternative vs null. Results are mean±SD.

RESULTS

Comparing baseline velocity (cm/s) between CAFF (9.3±4.8) and ABS (7.5±4.9) yielded anecdotal evidence (BF10 = 1.0). Peak hyperemic velocity (cm/s) was similar (CAFF = 77.3±16.7; ABS = 77.6±19.0, BF10 = 0.20). For slopes (TSI% /s), CAFF Slope 1 = -0.11±0.04 and Slope 2 = 1.9±0.46 were similar (both BF10≤0.20) to ABS Slope 1 = -0.12±0.03 and Slope 2 = 1.8±0.42. SBP and DBP (mmHg) were both similar (CAFF SBP = 116.0±9.8, DBP = 69.6±5.8; ABS SBP = 115.5±10.7, DBP = 69.5±5.4; both BF10≤0.22). Comparing AOP (mmHg) (CAFF = 146.6±15.0; ABS = 143.0±16.4) yielded anecdotal evidence (BF10 = 0.46). HR (bpm) was similar (CAFF = 66.5±12.3; ABS = 66.9±13.0; BF10 = 0.20).

CONCLUSIONS

In habitual users, consuming or abstaining from typical caffeine doses does not appear to affect post-occlusive reactive hyperemia.

Guarana (Paullinia cupana) but Not Low-Dose Caffeine Improves Cycling Time-Trial Performance Versus Placebo

Guarana (GUA) seed extract, containing caffeine (CAF) and additional bioactive compounds, may positively affect mental performance, but evidence regarding exercise is limited. This investigation assessed acute GUA ingestion compared with CAF on endurance performance. Eleven endurance-trained noncyclists and cyclists (V˙O2peak = 49.7 ± 5.9, 60.4 ± 4.6 ml·kg·min-1) completed a double-blind, crossover experiment after ingesting (a) 100 mg CAF, (b) 500 mg GUA (containing 130 mg CAF), or (c) placebo (P) prior to 60-min fixed cycling workload (FIX) + 15-min time trial. Oxygen uptake, heart rate, respiratory exchange ratio, blood glucose, and lactate were not different (p ≥ .052) during FIX. A significant interaction (p = .042) for perceived exertion was observed at 50-min FIX with lower rating (p = .023) for GUA versus CAF but not compared with P. Work accumulated over 15-min time trial was greater (p = .038) for GUA versus P due to higher early (1-11 min) work outputs. Work performance favored (effect size = 0.18; 95% confidence interval [0.003, 0.355], p = .046) GUA (241.4 ± 39.9 kJ) versus P (232.1 ± 46.6 kJ), but CAF (232.3 ± 43.9) was not different from GUA (effect size = 0.19; 95% confidence interval [-0.022, 0.410], p = .079) or P. Postexercise strength loss was not attenuated with GUA (-5.6 ± 8.5%) or CAF (-8.3 ± 9.4%) versus P (-10.3 ± 5.1%). Acute GUA ingestion improved work performance relative to P, but effects were trivial to small and unrelated to altered substrate oxidation or muscular strength. Ergogenicity may involve central mechanisms reducing perceived effort with GUA (containing 130 mg caffeine). Due to issues related to identical matching of dosage, whether GUA confers additional benefits beyond its CAF content cannot be determined at present.

Traversing the Cell Wall: The Chitinolytic Activity of Histoplasma capsulatum Extracellular Vesicles Facilitates Their Release

Histoplasma capsulatum is the causative agent of histoplasmosis. Treating this fungal infection conventionally has significant limitations, prompting the search for alternative therapies. In this context, fungal extracellular vesicles (EVs) hold relevant potential as both therapeutic agents and targets for the treatment of fungal infections. To explore this further, we conducted a study using pharmacological inhibitors of chitinase (methylxanthines) to investigate their potential to reduce EV release and its subsequent impact on fungal virulence in an in vivo invertebrate model. Our findings revealed that a subinhibitory concentration of the methylxanthine, caffeine, effectively reduces EV release, leading to a modulation of H. capsulatum virulence. To the best of our knowledge, this is the first reported instance of a pharmacological inhibitor that reduces fungal EV release without any observed fungicidal effects.

Caffeine Synthesis and Its Mechanism and Application by Microbial Degradation, A Review

Caffeine is a metabolite derived from purine nucleotides, typically accounting for 2-5% of the dry weight of tea and 1-2% of the dry weight of coffee. In the tea and coffee plants, the main synthesis pathway of caffeine is a four-step sequence consisting of three methylation reactions and one nucleosidase reaction using xanthine as a precursor. In bacteria, caffeine degradation occurs mainly through the pathways of N-demethylation and C-8 oxidation. However, a study fully and systematically summarizing the metabolism and application of caffeine in microorganisms has not been established elsewhere. In the present study, we provide a review of the biosynthesis, microbial degradation, gene expression, and application of caffeine microbial degradation. The present review aims to further elaborate the mechanism of caffeine metabolism by microorganisms and explore the development prospects in this field.

Cardiorespiratory and Neuroprotective Effects of Caffeine in Neonate Animal Models

Caffeine is widely used to improve neonatal health in animals with low vitality. Due to its pharmacokinetics and pharmacodynamics, caffeine stimulates the cardiorespiratory system by antagonism of adenosine receptors and alteration in Ca+2 ion channel activity. Moreover, the availability of intracellular Ca+2 also has positive inotropic effects by increasing heart contractibility and by having a possible positive effect on neonate vitality. Nonetheless, since neonatal enzymatic and tissular systems are immature at birth, there is a controversy about whether caffeine is an effective therapy for newborns. This review aims to analyze the basic concepts of caffeine in neonatal animal models (rat and mouse pups, goat kids, lambs, and piglets), and it will discuss the neuroprotective effect and its physiological actions in reducing apnea in newborns.

Could the serum glucose/potassium ratio offer an early reliable predictor of life-threatening events in acute methylxanthine intoxication?

Methylxanthines are widely used to manage pulmonary disorders, particularly in developing countries. Methylxanthines are unsafe due to their narrow therapeutic index and associated morbidity and mortality. The current study aimed to investigate the role of glucose/potassium ratio as a substantially useful early predictor of life-threatening events (LTEs) in the form of cardiovascular and neurological complications among methylxanthine users. A retrospective cohort study was conducted using medical records of patients diagnosed with acute methylxanthine intoxications and presented to an Egyptian Poison Control Center for 2 years. A total of 366 patients were enrolled. Of them, 59 patients (16.1%) were complicated with LTEs. The most frequent serious arrhythmia was T wave inversion (45.6% of patients with LTEs). Laboratory investigations that could significantly predict LTEs were the random blood glucose and potassium levels, glucose/potassium ratio, pH, liver transaminases, HCO3 level, hemoglobin, and platelet count (P < 0.05). The glucose/potassium ratio was the best predictor of LTEs (odds ratio = 2.92, and 95% confidence interval = 2.02-4.23). With an excellent area under the curve (0.906) and at a cutoff of 2.44, that ratio could correctly classify the patients based on their risk of LTEs with an overall accuracy of 73% (sensitivity of 88% and specificity of 70%). The current study endorsed an important, feasible, and easily obtainable ratio that could predictor stratify the patients according to severity and risk of LTEs, which guides the decision-making and prioritizes the treatment lines in methylxanthine intoxicated patients.

Metabolism of guarana (Paullinia cupana Kunth var. sorbilis) plants and fruit production subjected to glyphosate doses

Guarana (Paullinia cupana Kunth var. sorbilis) is a typically Amazonian plant of high economic value due to the compounds found in its seed. For guarana to reach the maximum productive potential, management practices such as weed control are necessary. The use of herbicides is a viable alternative, however, its drift may lead to adverse effects on the primary and secondary plant metabolisms and cause losses in crop production. This study evaluated the differential drift effects of glyphosate doses on the physiology of guarana plants and the production of compounds of economic interest in their seeds. Glyphosate doses (57.6, 115.2, 230.4, 460.8 g ae ha^-1) were applied to adult guarana plants after the flowering period. The photosynthetic functions and metabolism effects were evaluated. Herbicide treatments led to oxidative stress due to increased lipid peroxidation and increased carbohydrate and amino acid in their leaflets. Despite this, glyphosate showed no effect on fruit production or the content of secondary metabolites of commercial interest in seeds.

Paraxanthine safety and comparison to caffeine

Introduction: Caffeine, one of the most ubiquitous ingredients found in beverages and other ingested food products, has a long history of safe use. As a member of the methylxanthine class of stimulants, caffeine is not devoid of unwanted side effects at any serving level. Caffeine safety has been the subject of a safety workshop by FDA and the Institute of Medicine in the past decade. Thus, investigation into an alternate stimulant with similar pharmacology but improved safety is warranted. Paraxanthine (1,7-dimethylxanthine) is the predominant metabolite of caffeine in humans with similar stimulant properties. The few toxicity studies that are available for paraxanthine suggest that the molecule is relatively safe, although thorough characterization of its safety is required prior to widespread incorporation into foods/beverages. Methods: The aim of this study was to evaluate the toxicity of paraxanthine (Rarebird, Inc.) relative to caffeine through a battery of toxicological studies conducted in accordance with international guidelines. These studies evaluated the potential mutagenicity (bacterial reverse mutation, in vitro mammalian chromosomal aberration), genetic toxicity (in vitro mammalian cell gene mutation) and acute, sub-acute and sub-chronic oral toxicity of paraxanthine in Sprague Dawley rats. Results/Discussion: There was no evidence of genetic toxicity or mutagenicity in the in vitro studies. An acute oral LD₅₀ of 829.20 mg/kg body weight (bw) was established. There was no mortality or treatment-related adverse effects in the 14-day repeat dose oral toxicity study, wherein rats received low, mid, or high doses of paraxanthine (50, 100, or 150 mg/kg bw, n = 5 rats/sex/group). The same findings were observed in the subchronic repeat-dose 90-day oral toxicity study at daily doses of paraxanthine of 100, 150, or 185 mg/kg bw which were compared to caffeine at 150 or 185 mg/kg bw (n = 10 animals/sex/group). However, mortality was reported in two animals in the high dose caffeine-treated animals. Therefore, the no observed adverse effect level (NOAEL) from the 90-day study was determined to be 150 mg/kg bw for caffeine and 185 mg/kg bw for paraxanthine for both male and female Sprague Dawley rats. These findings may suggest that paraxanthine could be a safer alternative to caffeine in humans.

From Cocoa to Chocolate: Effect of Processing on Flavanols and Methylxanthines and Their Mechanisms of Action

Despite the health benefits associated with the ingestion of the bioactive compounds in cocoa, the high concentrations of polyphenols and methylxanthines in the raw cocoa beans negatively influence the taste, confer the astringency and bitterness, and affect the stability and digestibility of the cocoa products. It is, therefore, necessary to process cocoa beans to develop the characteristic color, taste, and flavor, and reduce the astringency and bitterness, which are desirable in cocoa products. Processing, however, affects the composition and quantities of the bioactive compounds, resulting in the modification of the health-promoting properties of cocoa beans and chocolate. In this advanced review, we sought to better understand the effect of cocoa's transformational process into chocolate on polyphenols and methylxanthine and the mechanism of action of the original flavanols and methylxanthines. More data on the cocoa processing effect on cocoa bioactives are still needed for better understanding the effect of each processing step on the final polyphenolic and methylxanthine composition of chocolate and other cocoa products. Regarding the mechanisms of action, theobromine acts through the modulation of the fatty acid metabolism, mitochondrial function, and energy metabolism pathways, while flavanols mainly act though the protein kinases and antioxidant pathways. Both flavanols and theobromine seem to be involved in the nitric oxide and neurotrophin regulation.

Quantitative analysis and response surface modeling of important bitter compounds in chocolate made from cocoa beans with eight roast profiles across three origins

Eight different roast profiles for each of the three origins of cacao were prepared and made into unsweetened chocolate based upon an I-Optimal response-surface design for minimizing prediction variance. Quantitative chemical analysis of all chocolate treatments was performed with HPLC-DAD on six important bitter compounds (i.e., theobromine, caffeine, epicatechin, catechin, procyanidin B2, and cyclo(Proline-Valine)). Least-squares linear modeling was then performed. Using derived linear models, response-surface contour plots were produced to show predicted changes in the six bitter compounds over the entire experimental region. Significant and large decreases in concentration of epicatechin and procyanidin B2 were observed as roasting progressed, whereas for catechin and cyclo(Proline-Valine), significant increases were observed. Small yet significant theobromine and caffeine concentration increases were also observed with roasting, likely due to moisture loss. Some significant differences were also found between the cacao origins for all bitter compound concentrations except for cyclo(Proline-Valine), suggesting the importance of a survey encompassing a greater number of cacao origins in the future to obtain a more complete picture of the variation in bitter compounds in cacao due to origin. PRACTICAL APPLICATION: This research describes how roasting can be used to alter the concentration of bitter and sometimes astringent chemicals for several origins of cacao, which may be used to improve the sensory characteristics of dark chocolate.

The possible effect of pentoxifylline on development and severity of retinopathy of prematurity

BACKGROUND AND AIM

Retinopathy of prematurity (ROP) is the major ocular problem of preterm infants that occurs with abnormal proliferation of immature retinal vessels. Although pentoxifylline (PTX) was reported to inhibit vasculogenesis and neovascularization in experimental studies, there is no clinical data about the effects of PTX treatment on the development and severity of ROP. This clinical study aimed to investigate the possible effects of PTX on the development of ROP.

MATERIALS AND METHODS

A single-centre retrospective study was conducted including preterm infants who were hospitalised in the neonatal intensive care unit between 2015-2017 years. Infants were divided into two groups in terms of PTX administration for adjuvant therapy, as PTX and non-PTX groups.

RESULTS

A total of 211 infants were included in the study [gestational age 29 (27-31) weeks, birth weight 1140 (960-1340) g]. From these, 97 infants (46%) were given PTX treatment. The two groups were similar in terms of demographic data and baseline clinical characteristics. Any stage of ROP was detected in 47.4% of infants in the PTX group, which was significantly higher than those in the non-PTX group (27.2%) (p = 0.002). The incidence of advanced-stage ROP in the PTX group (10.3%) was also higher than in the non-PTX group (2.6%) (p = 0.021). Repeated usage of PTX was not found to be related to the development of ROP (p = 0.059). The time of PTX administration was similar between the ROP and no-ROP groups (median; one vs one week, p = 0.825). Surfactant therapy, duration of hospital stay, and PTX treatment were found as significant risk factors for ROP in the logistic regression analysis.

CONCLUSIONS

In contrast to the experimental studies and also promising results of PTX treatment in some neonatal morbidities, it may be associated with increased incidence and stage of ROP.

The Effects of Caffeine on Jumping Performance and Maximal Strength in Female Collegiate Athletes

Caffeine is often used in a variety of forms to enhance athletic performance; however, research regarding caffeine's effects on strength and power in female athletes is lacking. Therefore, the purpose of this study was to analyze the acute effects of caffeine anhydrous (6 mg/kg of body mass) on jumping performance and maximal strength in female collegiate athletes. Eleven athletes (19.7 ± 0.9 yrs; 166.4 ± 10.2 cm, 67.7 ± 9.4 kg) performed two testing sessions separated by one week, and randomly received caffeine or placebo using a double-blind approach. Heart rate, blood pressure, and tympanic temperature were recorded before athletes received each condition, following 60 min of quiet sitting, and directly after performance testing. Athletes were assessed on unweighted and weighted squat jump height (SJH0, SJH20) and countermovement jump height (CMJH0, CMJH20), isometric mid-thigh pull peak force (IPF), and rate of force development from 0-200 ms (RFD200). Resting systolic blood pressure was significantly greater following caffeine administration compared to a placebo (p = 0.017). There were small, significant differences in SJH0 (p = 0.035, g = 0.35), SJH20 (p = 0.002, g = 0.49), CMJH0 (p = 0.015, g = 0.19), and CMJH20 (p < 0.001, g = 0.37) in favor of caffeine over placebo. However, there was no significant difference in IPF (p = 0.369, g = 0.12) and RFD200 (p = 0.235, g = 0.32) between conditions. Therefore, caffeine appears to enhance jumping performance, but not maximal strength in female collegiate athletes.

The Neurophysiology of Caffeine as a Central Nervous System Stimulant and the Resultant Effects on Cognitive Function

Caffeine is one of the world’s most consumed drugs. According to the Washington Post (2015), two billion cups of coffee are consumed per day worldwide. Caffeine is classified as a central nervous system (CNS) stimulant and an organic molecule called methylxanthine. Caffeine has three notable mechanisms of action on the CNS that produce a psychostimulant effect. These effects are responsible for the effect that caffeine has on cognitive function. The effects of caffeine consumption on cognitive function have been demonstrated across several studies involving humans and animals. With the immense number of people consuming caffeine around the world, it is of vital importance to study the effects that this drug has on people’s cognitive function. This literature review provides useful insights on this question through the analysis of caffeine’s effects on cognitive function, along with information on caffeine’s three modes of action. The findings of recent studies show mixed results regarding the effects of caffeine on mood, attention, processing speed, and memory. Current research suggests that if caffeine does have an effect on mood, the most significant changes may be anxiety. Studies did not support caffeine as having any significant effect on attention, but that it did play a role in enhancing processing speed. The majority of the studies reviewed suggest caffeine as having a significant positive effect on both short and long-term memory in adults and the elderly. Current findings warrant continued research on the association of caffeine and the resultant effects on cognitive function.

Natural Compounds as Guides for the Discovery of Drugs Targeting G-Protein-Coupled Receptors

G protein-coupled receptors (GPCRs), which constitute the most populous family of the human proteome, are the target of 35–45% of approved therapeutic drugs. This review focuses on natural products (excluding peptides) that target GPCRs. Natural compounds identified so far as agonists, antagonists or allosteric modulators of GPCRs have been found in all groups of existing living beings according to Whittaker’s Five Kingdom Classification, i.e., bacteria (monera), fungi, protoctists, plants and animals. Terpenoids, alkaloids and flavonoids are the most common chemical structures that target GPCRs whose endogenous ligands range from lipids to epinephrine, from molecules that activate taste receptors to molecules that activate smell receptors. Virtually all of the compounds whose formula is displayed in this review are pharmacophores with potential for drug discovery; furthermore, they are expected to help expand the number of GPCRs that can be considered as therapeutic targets.

Terbutaline and aminophylline as second-line therapies for status asthmaticus in the pediatric intensive care unit

OBJECTIVE

Asthma is the most common chronic disease of childhood. Although asthma admissions to the pediatric intensive care unit (PICU) are increasing, there are no evidence-based guidelines on preferred escalation of therapies for patients with status asthmaticus who fail to respond to inhaled bronchodilators and systemic corticosteroids. The purpose of this study was to assess outcomes of PICU patients receiving aminophylline versus terbutaline as second-tier therapies for status asthmaticus.

DESIGN

Retrospective cohort study using Pediatric Health Information System from 2016-2019.

SETTING

Fifty-three tertiary children's hospitals.

SUBJECTS

Children aged 2 to 18 years admitted to the PICU in children's hospitals contributing data to the Pediatric Health Information System with a primary diagnosis of status asthmaticus.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 11 133 pediatric patients treated for status asthmaticus in the PICU during the study period, 1144 received either terbutaline or aminophylline. There was no difference in intubation and mechanical ventilation between patients who received aminophylline and those who received terbutaline. However, in African American patients, those who received terbutaline had a significantly higher odds of intubation and mechanical ventilation compared to those who received aminophylline (OR, 12.41; 95%CI, 1.61,95).

CONCLUSIONS

The use of aminophylline is associated with lower odds of intubation and mechanical ventilation in African American patients with status asthmaticus as compared to terbutaline.

Caffeine Therapy in Preterm Infants: The Dose (and Timing) Make the Medicine

Caffeine is one of the most commonly utilized medications in the NICU. In preterm infants, short-term and long-term pulmonary and neurodevelopmental benefits of therapy are well documented in the literature. While robust evidence supports the use of standard doses of caffeine for apnea of prematurity or to facilitate successful extubation, much remains unknown regarding the boundaries of efficacy and safety for this common therapeutic agent. Escalating dosing regimens seem to provide additional benefit in select infants, but grave toxicity has also been documented with early utilization of high-dose caffeine. Conflicting data exist surrounding the ideal timing of initiation of therapy. Even the widely adhered to discontinuation point has been challenged by data supporting continued use. Until robust data definitively support change, practice should align with current evidence defining clear, safe, and efficacious dosing and timing of caffeine therapy.

Methylxanthines Inhibit Primary Amine Oxidase and Monoamine Oxidase Activities of Human Adipose Tissue

Background: Methylxanthines including caffeine and theobromine are widely consumed compounds and were recently shown to interact with bovine copper-containing amine oxidase. To the best of our knowledge, no direct demonstration of any interplay between these phytochemicals and human primary amine oxidase (PrAO) has been reported to date. We took advantage of the coexistence of PrAO and monoamine oxidase (MAO) activities in human subcutaneous adipose tissue (hScAT) to test the interaction between several methylxanthines and these enzymes, which are involved in many key pathophysiological processes. Methods: Benzylamine, methylamine, and tyramine were used as substrates for PrAO and MAO in homogenates of subcutaneous adipose depots obtained from overweight women undergoing plastic surgery. Methylxanthines were tested as substrates or inhibitors by fluorimetric determination of hydrogen peroxide, an end-product of amine oxidation. Results: Semicarbazide-sensitive PrAO activity was inhibited by theobromine, caffeine, and isobutylmethylxanthine (IBMX) while theophylline, paraxanthine, and 7-methylxanthine had little effect. Theobromine inhibited PrAO activity by 54% at 2.5 mM. Overall, the relationship between methylxanthine structure and the degree of inhibition was similar to that seen with bovine PrAO, although higher concentrations (mM) were required for inhibition. Theobromine also inhibited oxidation of tyramine by MAO, at the limits of its solubility in a DMSO vehicle. At doses higher than 12 % v/v, DMSO impaired MAO activity. MAO was also inhibited by millimolar doses of IBMX, caffeine and by other methylxanthines to a lesser extent. Conclusions: This preclinical study extrapolates previous findings with bovine PrAO to human tissues. Given that PrAO is a potential target for anti-inflammatory drugs, it indicates that alongside phosphodiesterase inhibition and adenosine receptor antagonism, PrAO and MAO inhibition could contribute to the health benefits of methylxanthines, especially their anti-inflammatory effects.

The efficacy of adding budesonide/formoterol to ipratropium plus theophylline in managing severe chronic obstructive pulmonary disease: an open-label, randomized study in China

Background:

Patients diagnosed with chronic obstructive pulmonary disease (COPD) in China are commonly prescribed ipratropium plus theophylline (I+T) therapy. Studies have shown that an inhaled corticosteroid (ICS)/long-acting β²-agonist (LABA) combination is also efficacious in reducing symptoms and exacerbations. This study evaluated the efficacy and tolerability of adding budesonide/formoterol (BUD/FORM) to I+T in Chinese patients with severe COPD.

Methods:

A randomized, parallel-group, open-label, multicenter phase IV study (Clinical Trials.gov identifier: NCT01415518) was conducted in China. Patients received either BUD/FORM (160/4.5 µg; two inhalations twice daily [bid] via Turbuhaler^®) + I (20 µg per inhalation, two inhalations four times daily) + T (100 mg bid) or I+T alone for 12 weeks. The primary efficacy variable was change from baseline in predose forced expiratory volume in 1 s (FEV₁).

Results:

A total of 584 patients were randomized equally between treatment groups. At the end of the study, the BUD/FORM plus I+T group displayed significant improvements in predose FEV₁ versus the I+T group (between-group difference 6.9%; 95% confidence interval [CI]: 4.3, 9.6; p < 0.0001). Forced vital capacity, inspiratory capacity, peak expiratory flow and health-related quality of life (HRQoL) scores were significantly improved (all p < 0.0001) and exacerbation frequency was reduced (43.5% reduction; rate ratio 0.565, 95% CI 0.325, 0.981; p = 0.0425) with BUD/FORM plus I+T versus I+T alone.

Conclusion:

Patients with severe COPD in China treated with BUD/FORM plus I+T showed significant improvements in lung function and HRQoL and a reduction in exacerbations compared with I+T alone. Both treatments were well tolerated and no safety concerns were noted.

The reviews of this paper are available via the supplemental material section.

Bioassay for Determining the Concentrations of Caffeine and Individual Methylxanthines in Complex Samples

Caffeine and other methylxanthines are stimulant molecules found in formulated beverages, including sodas and energy drinks, and in brewed beverages, such as coffee and teas. Previously, we developed a bioassay for caffeine that involves monitoring the growth of a ΔguaB mutant of Escherichia coli defective in de novo guanine biosynthesis. When supplemented with a plasmid expressing the genes for an N-demethylation pathway from Pseudomonas putida CBB5, these bacteria demethylate caffeine (1,3,7-trimethylxanthine) and other methylxanthines into xanthine, which is then converted into guanine to support cell growth. A major limitation of this bioassay was that it could only measure the total concentration of all methylxanthines in a mixture. Therefore, it could not be used to measure the caffeine content of beverages like teas, which contain substantial quantities of multiple methylxanthines. To overcome this limitation, we created seven new plasmids containing all subsets of the three demethylase genes (ndmA, ndmB, and ndmC). We show that strains of ΔguaB E. coli containing each plasmid are able to demethylate specific subsets of methylxanthines and that they can be used to determine the concentrations of individual methylxanthines in complex mixtures containing multiple methylxanthines, including coffee doped with an additional methylxanthine. While validating this assay, we also discovered an unexpected demethylation event at the 1-methyl position when NdmB and NdmC were expressed in the absence of NdmA. The improved cell-based bioassay is inexpensive, is easy to use, and gives results comparable to standard high-performance liquid chromatography methods for measuring methylxanthine concentrations.IMPORTANCE Caffeine (1,3,7-trimethylxanthine) is the dominant neurostimulant found in coffee, teas, sodas, and energy drinks. Measuring the amount of caffeine and other methylxanthines in these beverages is important for quality assurance and safety in food science. Methylxanthines are also used in medicine and as performance-enhancing drugs, two contexts in which accurately determining their concentrations in bodily fluids is important. Liquid chromatography is the standard method for measuring methylxanthine concentrations in a sample, but it requires specialized equipment and expertise. We improved a previous bioassay that links E. coli growth to methylxanthine demethylation so that it can now be used to determine the amounts of individual methylxanthines in complex mixtures or beverages, such as coffee.

Incidence and Risk Factors of Early Onset Neonatal AKI

BACKGROUND AND OBJECTIVES

Neonatal AKI is associated with poor short- and long-term outcomes. The objective of this study was to describe the risk factors and outcomes of neonatal AKI in the first postnatal week.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The international retrospective observational cohort study, Assessment of Worldwide AKI Epidemiology in Neonates (AWAKEN), included neonates admitted to a neonatal intensive care unit who received at least 48 hours of intravenous fluids. Early AKI was defined by an increase in serum creatinine >0.3 mg/dl or urine output <1 ml/kg per hour on postnatal days 2-7, the neonatal modification of Kidney Disease: Improving Global Outcomes criteria. We assessed risk factors for AKI and associations of AKI with death and duration of hospitalization.

RESULTS

Twenty-one percent (449 of 2110) experienced early AKI. Early AKI was associated with higher risk of death (adjusted odds ratio, 2.8; 95% confidence interval, 1.7 to 4.7) and longer duration of hospitalization (parameter estimate: 7.3 days 95% confidence interval, 4.7 to 10.0), adjusting for neonatal and maternal factors along with medication exposures. Factors associated with a higher risk of AKI included: outborn delivery; resuscitation with epinephrine; admission diagnosis of hyperbilirubinemia, inborn errors of metabolism, or surgical need; frequent kidney function surveillance; and admission to a children's hospital. Those factors that were associated with a lower risk included multiple gestations, cesarean section, and exposures to antimicrobials, methylxanthines, diuretics, and vasopressors. Risk factors varied by gestational age strata.

CONCLUSIONS

AKI in the first postnatal week is common and associated with death and longer duration of hospitalization. The AWAKEN study demonstrates a number of specific risk factors that should serve as "red flags" for clinicians at the initiation of the neonatal intensive care unit course.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Assessment of Worldwide AKI Epidemiology in Neonates (AWAKEN), NCT02443389.

LC-MS Metabolomics and Chemotaxonomy of Caffeine-Containing Holly ( Ilex) Species and Related Taxa in the Aquifoliaceae

Ilex species have been consumed traditionally as medicinal teas worldwide. Though the presence of caffeine has been reported in several species, little is known about secondary-metabolite diversity within and among these taxa. Leaf samples of Ilex guayusa, Ilex paraguariensis, and Ilex vomitoria were analyzed by liquid chromatography-mass spectrometry and comparative metabolite profiling with Ilex cassine and other Ilex species to identify chemotaxonomic markers, delimit species, and provide an assessment of chemodiversity. Purine alkaloids were detected and quantified in I. guayusa, I. paraguariensis, and I. vomitoria. Reports of caffeine for I. cassine were not corroborated, suggesting that I. vomitoria was the traditional source of the Native North American tea yaupon. The tetramethyluric acid, theacrine, was detected for the first time in the genus Ilex as a low-level chemotaxonomic marker in I. vomitoria samples. Chemotaxonomy and metabolomics support a close relationship for caffeine-containing Ilex species.

Role of Theobromine in Cocoa's Metabolic Properties in Healthy Rats

Cocoa is rich in polyphenols and methylxanthines, and it has been reported that its consumption, among other properties, has beneficial effects on metabolism. This study aimed to investigate the role of theobromine in cocoa's metabolic properties in healthy rats. In addition to morphometric measurements, biochemical markers of lipids and glucose metabolism and gene expression of molecules related to immune cells in adipose and hepatic tissues were assessed after 7 or 18 days of diet. Additionally, a metabolomic analysis was carried out at day 7. This study revealed the presence of six discriminant metabolites in plasma due to the diets. Moreover, the results showed that theobromine is the main responsible factor for cocoa's effects on body weight gain as well as on lipid and glucose metabolism. The effects on body weight and lipids appeared as early as after 7 days of diet, whereas those affecting glucose metabolism required a longer intervention.

Methylxanthine use for acute asthma in the emergency department in Japan: a multicenter observational study

Aim

Methylxanthines are no longer recommended for emergency department (ED) patients with acute asthma according to international guidelines. We aimed to describe the current methylxanthine use for acute asthma and to determine factors related to its use in the ED.

Methods

We undertook a multicenter retrospective study in 23 EDs across Japan. From each participating hospital, we randomly identified 60 ED patients aged 18-54 years with acute asthma from 2009 through 2011. We examined the associations of ED and patient characteristics with methylxanthine use by constructing a multivariable logistic regression model adjusting for a predefined set of ED- and patient-level factors.

Results

Among 1,380 patients, methylxanthines were used for 79 patients (5.7%, 95% confidence interval [CI], 4.6-7.0%). The proportion of methylxanthine treatment varied substantially among EDs, ranging from 0% to 26.1%. In the multivariable analysis, the number of annual ED patients with acute asthma (odds ratio [OR] per 100 increase in annual asthma patients, 0.12; 95% CI, 0.04-0.34; P < 0.001) and having a protocol for asthma treatment (OR 2.91; 95% CI, 1.06-8.00; P = 0.04) at the ED level, and systemic corticosteroid use (OR 6.39; 95% CI, 3.34-12.22; P < 0.001) at the patient level were associated with likelihood of methylxanthine use.

Conclusions

In this multicenter study, approximately 6% of ED patients with acute asthma were treated with methylxanthines, with a wide variation across EDs. The number of annual ED patients with acute asthma was significantly associated with a lower likelihood of methylxanthine use, whereas having an ED asthma treatment protocol and systemic corticosteroid use in the ED were associated with a higher likelihood of methylxanthine treatment.

Incidence and Risk Factors of Early Onset Neonatal AKI

BACKGROUND AND OBJECTIVES

Neonatal AKI is associated with poor short- and long-term outcomes. The objective of this study was to describe the risk factors and outcomes of neonatal AKI in the first postnatal week.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The international retrospective observational cohort study, Assessment of Worldwide AKI Epidemiology in Neonates (AWAKEN), included neonates admitted to a neonatal intensive care unit who received at least 48 hours of intravenous fluids. Early AKI was defined by an increase in serum creatinine >0.3 mg/dl or urine output <1 ml/kg per hour on postnatal days 2-7, the neonatal modification of Kidney Disease: Improving Global Outcomes criteria. We assessed risk factors for AKI and associations of AKI with death and duration of hospitalization.

RESULTS

Twenty-one percent (449 of 2110) experienced early AKI. Early AKI was associated with higher risk of death (adjusted odds ratio, 2.8; 95% confidence interval, 1.7 to 4.7) and longer duration of hospitalization (parameter estimate: 7.3 days 95% confidence interval, 4.7 to 10.0), adjusting for neonatal and maternal factors along with medication exposures. Factors associated with a higher risk of AKI included: outborn delivery; resuscitation with epinephrine; admission diagnosis of hyperbilirubinemia, inborn errors of metabolism, or surgical need; frequent kidney function surveillance; and admission to a children's hospital. Those factors that were associated with a lower risk included multiple gestations, cesarean section, and exposures to antimicrobials, methylxanthines, diuretics, and vasopressors. Risk factors varied by gestational age strata.

CONCLUSIONS

AKI in the first postnatal week is common and associated with death and longer duration of hospitalization. The AWAKEN study demonstrates a number of specific risk factors that should serve as "red flags" for clinicians at the initiation of the neonatal intensive care unit course.

Prescription Status and Clinical Outcomes of Methylxanthines and Leukotriene Receptor Antagonists in Mild-to-Moderate Chronic Obstructive Pulmonary Disease

BACKGROUND

Methylxanthines and leukotriene receptor antagonists (LTRA) are not a first-line medical treatment for chronic obstructive pulmonary disease (COPD) but are frequently prescribed despite limited evidence. We aimed to elucidate the real prescribing status and clinical impacts of these agents in early COPD patients.

METHODS

Patients with mild-to-moderate COPD (FEV₁>50%) were selected from the Korean National Health and Nutrition Examination Survey data between 2007 and 2012. Besides analyzing the prescription status of methylxanthines and LTRA and the contributing factors to the prescription, we evaluated the clinical impacts of these drugs on the exacerbation, hospitalization, and medical costs.

RESULTS

Of 2269 patients with mild-to-moderate COPD, 378 patients (16.7%) were under medical treatments, and the users of methylxanthines and/or LTRA were 279 patients (12.3%); however, only 139 patients (6.1%) were inhaler users. The contributing factors for the prescription of methylxanthines were a comorbidity of asthma or allergic disease, poor lung function, low quality of life, prescribing doctor from the specialty of internal medicine, and an institution type of private hospital. The prescription of LTRA was associated with the comorbidity of allergic disease. The methylxanthine and/or LTRA users had more hospital utilization but did not have significant differences in acute exacerbations and medical cost for hospital utilization, compared with the non-users.

CONCLUSION

Methylxanthines and LTRA were used in a significant proportion of patients with mild-to-moderate COPD in real fields without favorable impacts on the exacerbations, hospitalizations, or medical costs. The use of more effective inhaled medications should be encouraged.

Caffeine and Physiological Responses to Submaximal Exercise: A Meta-Analysis

The aim of this study was to carry out a systematic review and meta-analysis of the effects of caffeine supplementation on physiological responses to submaximal exercise. A total of 26 studies met the inclusion criteria of adopting double-blind, randomized crossover designs that included a sustained (5-30 min) fixed-intensity bout of submaximal exercise (constrained to 60-85% maximal rate of oxygen consumption) using a standard caffeine dose of 3-6 mg·kg^-1 administered 30-90 min prior to exercise. Meta-analyses were completed using a random-effects model, and data are presented as raw mean difference (D) with associated 95% confidence limits (CLs). Relative to placebo, caffeine led to significant increases in submaximal measures of minute ventilation (D = 3.36 L·min^-1; 95% CL, 1.63-5.08; P = .0001; n = 73), blood lactate (D = 0.69 mmol·L^-1; 95% CL, 0.46-0.93; P < .00001; n = 208), and blood glucose (D = 0.42 mmol·L^-1; 95% CL, 0.29-0.55; P < .00001; n = 129). In contrast, caffeine had a suppressive effect on ratings of perceived exertion (D = -0.8; 95% CL, -1.1 to -0.6; P < .00001; n = 147). Caffeine had no effect on measures of heart rate (P = .99; n = 207), respiratory exchange ratio (P = .18; n = 181), or oxygen consumption (P = .92; n = 203). The positive effects of caffeine supplementation on sustained high-intensity exercise performance are widely accepted, although the mechanisms to explain that response are currently unresolved. This meta-analysis has revealed clear effects of caffeine on various physiological responses during submaximal exercise, which may help explain its ergogenic action.

Pharmacological potential of methylxanthines: Retrospective analysis and future expectations

Methylated xanthines (methylxanthines) are available from a significant number of different botanical species. They are ordinarily included in daily diet, in many extremely common beverages and foods. Caffeine, theophylline and theobromine are the main methylxanthines available from natural sources. The supposedly relatively low toxicity of methylxanthines, combined with the many beneficial effects that have been attributed to these compounds through time, generated a justified attention and a very prolific ground for dedicated scientific reports. Methylxanthines have been widely used as therapeutical tools, in an intriguing range of medicinal scopes. In fact, methylxanthines have been/were medically used as Central Nervous System stimulants, bronchodilators, coronary dilators, diuretics and anti-cancer adjuvant treatments. Other than these applications, methylxanthines have also been hinted to hold other beneficial health effects, namely regarding neurodegenerative diseases, cardioprotection, diabetes and fertility. However, it seems now consensual that toxicity concerns related to methylxanthine consumption and/or therapeutic use should not be dismissed. Taking all the knowledge and expectations on the potential of methylxanthines into account, we propose a systematic look at the past and future of methylxanthine pharmacologic applications, discussing all the promise and anticipating possible constraints. Anyways, methylxanthines will still substantiate considerable meaningful research and discussion for years to come.

[Comparative Study of the Efficacy and Safety of Caffeine and Aminophylline for the Treatment of Apnea in Preterm Infants]

　Methylxanthine is widely administered for the treatment of apnea of prematurity in many countries, and previous reports have clearly established that caffeine is effective for the treatment of apnea of prematurity. In Japan, caffeine has been available since December 2014. Thus, we compared the efficacy and safety of caffeine with that of aminophylline in our hospital. There was no significant difference between the caffeine group and aminophylline group regarding the characteristics of the study patients. The mean efficacy rate from day 1 to day 10 was 89.5% in the caffeine group, and 81.9% in the aminophylline group, although the rate of improvement in apnea episodes each day from day 1 to day 10 was not significantly different between the two groups. On the other hand, the adverse event rates in the caffeine group and the aminophylline group were 70.6% and 75.0%, respectively. No significant difference was observed in the adverse event rates between the two groups. Moreover, suspected abdominal distension due to the drug administration was more frequently observed with the aminophylline group. Our findings indicate that caffeine is as effective as aminophylline, while it is superior to aminophylline regarding its overall safety.

Caffeine Modulates Food Intake Depending on the Context That Gives Access to Food: Comparison With Dopamine Depletion

Caffeine is a methylxanthine consumed in different contexts to potentiate alertness and reduce fatigue. However, caffeine can induce anxiety at high doses. Caffeine is also a minor psychostimulant that seems to act as an appetite suppressant, but there are also reports indicating that it could stimulate appetite. Dopamine also is involved in food motivation and in behavioral activation. In the present series of experiments, we evaluated the effects of acute administration of caffeine on food consumption under different access conditions. CD1 male adult mice had access to highly palatable food (50% sucrose) in a restricted but habitual context, under continuous or intermittent access as well as under anxiogenic, or effortful conditions. Caffeine (2.5-20.0 mg/kg) increased intake at the highest dose under familiar continuous and intermittent access. However, this high dose reduced food intake in the dark-light paradigm. In contrast, a dopamine-depleting agent, tetrabenazine (TBZ; 1.0-8.0 mg/kg) did not affect food intake in any of those experimental conditions. In the T-maze-barrier task that evaluates seeking and taking of food under effortful conditions, caffeine (10.0 mg/kg) decreased latency to reach the food, but did not affect selection of the high-food density arm that required more effort, or the total amount of food consumed. In contrast, TBZ (4.0 mg/kg) reduced selection of the high food density arm with the barrier, thus affecting amount of food consumed. Interestingly, a small dose of caffeine (5.0 mg/kg) was able to reverse the anergia-inducing effects produced by TBZ in the T-maze. These results suggest that caffeine can potentiate or suppress food consumption depending on the context. Moreover, caffeine did not change appetite, and did not impair orientation toward food under effortful conditions, but it rather helped to achieve the goal by improving speed and by reversing performance to normal levels when fatigue was induced by dopamine depletion.

Methylxanthine Content in Commonly Consumed Foods in Spain and Determination of Its Intake during Consumption

Methylxanthines present psychostimulant effects. These compounds have low toxicity and their consumption at moderate levels presents some beneficial health effects, whereas some significant risk appears at high levels. Samples of common types of methylxanthine-containing beverages and foods consumed in Spain were analyzed to determine their content. Caffeine was the methylxanthine that was most found in the samples investigated. Instant coffees gave the highest caffeine percentage (18–44 mg·g⁻¹). Green and scented teas were found to have a caffeine dry-weight content (8–26 mg·g⁻¹) equivalent to ground coffees (13–23 mg·g⁻¹), but black and pu-erh teas (18–30 mg·g⁻¹) had a higher caffeine content. The evaluation of the most conventional methods for preparing espresso coffees showed that an espresso contains between 88–116 mg of caffeine. In the case of tea beverages, the amount of caffeine present was 2–3 times smaller than in espresso coffees. Energy drinks showed a similar caffeine content (80–106 mg) as espresso coffees. Chocolates had the lowest caffeine content. It has been found that none of the foods evaluated reach the recommended daily intake limit of 400 mg of caffeine with a single dose. This limit can be reached with 4–5 doses in the case of coffees and energy drinks. In the case of chocolates, the methylxanthine compound detected at large levels was theobromine, with amounts ranging from 4 to 10 mg·g⁻¹ for dark chocolates.

Early Caffeine Prophylaxis and Risk of Failure of Initial Continuous Positive Airway Pressure in Very Low Birth Weight Infants

OBJECTIVE

To test the hypothesis that early caffeine treatment on the day of birth, compared with later treatment in very low birth weight (VLBW, <1500 g) infants receiving continuous positive airway pressure (CPAP) therapy, is associated with a decreased risk of CPAP failure in the first week of life.

STUDY DESIGN

Multicenter, observational cohort study in 366 US neonatal intensive care units. We evaluated inborn, VLBW infants discharged from 2000 to 2014, who received only CPAP therapy without surfactant treatment on day of life (DOL) 0, had a 5-minute Apgar ≥3, and received caffeine in the first week of life. We used multivariable conditional logistic regression to compare the risk of CPAP failure, defined as invasive mechanical ventilation or surfactant therapy on DOL 1-6, by timing of caffeine treatment as either early (initiation on DOL 0) or routine (initiation on DOL 1-6).

RESULTS

We identified 11 133 infants; 4528 (41%) received early caffeine and 6605 (59%) received routine caffeine. Median gestational age was lower in the early caffeine group, 29 weeks (25th, 75th percentiles; 28, 30) vs the routine caffeine group, 30 weeks (29, 31); P < 0.001. The incidence of CPAP failure on DOL 1-6 was similar between the early and routine caffeine groups: 22% vs 21%; adjusted OR = 1.05 (95% CI: 0.93, 1.18).

CONCLUSIONS

Early caffeine treatment on the day of birth was not associated with a decreased risk of CPAP failure in the first week of life for VLBW infants initially treated with CPAP.

Theophylline exhibits anti-cancer activity via suppressing SRSF3 in cervical and breast cancer cell lines

Caffeine, theophylline, and theobromine are the most well-known members of methylxanthines. Caffeine-induced serine/arginine-rich splicing factor 2, SRSF2, and SRSF3 are required for the alternative splicing of a subset of cancer-associated genes. However, it remains to be investigated whether and how theophylline and theobromine as well as caffeine exert their antitumor effects through mediating the alternative splicing process. Here, we reveal that theophylline down-regulated SRSF3 expression and switched p53 from alpha into a beta isoform as caffeine did in HeLa and MCF-7 cells via the reverse-transcriptase polymerase chain reaction and Western blot analysis. Further functional studies show that theophylline induced cellular apoptosis, senescence, and decreased colony formation. Interestingly, theophylline had a suppressive effect on cellular proliferation, whereas caffeine enhanced cellular proliferation rates via the 5-bromo-2-deoxyuridine analysis. Theophylline and caffeine had no effect on MCF-10A cells, which is a normal breast cell line. Our results provide an insight that theophylline as well as caffeine could be repurposed as antitumor leading compounds via the downregulation of splicing factor SRSF3 and its target genes.

Zebrafish Embryo as an In Vivo Model for Behavioral and Pharmacological Characterization of Methylxanthine Drugs

Zebrafish embryo is emerging as an important tool for behavior analysis as well as toxicity testing. In this study, we compared the effect of nine different methylxanthine drugs using zebrafish embryo as a model. We performed behavioral analysis, biochemical assay and Fish Embryo Toxicity (FET) test in zebrafish embryos after treatment with methylxanthines. Each drug appeared to behave in different ways and showed a distinct pattern of results. Embryos treated with seven out of nine methylxanthines exhibited epileptic-like pattern of movements, the severity of which varied with drugs and doses used. Cyclic AMP measurement showed that, despite of a significant increase in cAMP with some compounds, it was unrelated to the observed movement behavior changes. FET test showed a different pattern of toxicity with different methylxanthines. Each drug could be distinguished from the other based on its effect on mortality, morphological defects and teratogenic effects. In addition, there was a strong positive correlation between the toxic doses (TC₅₀) calculated in zebrafish embryos and lethal doses (LD₅₀) in rodents obtained from TOXNET database. Taken together, all these findings elucidate the potentiality of zebrafish embryos as an in vivo model for behavioral and toxicity testing of methylxanthines and other related compounds.

Effect of Catechins, Green tea Extract and Methylxanthines in Combination with Gentamicin Against Staphylococcus aureus and Pseudomonas aeruginosa: - Combination therapy against resistant bacteria

Objectives:

Bacterial resistant infections have become a global health challenge and threaten the society’s health. Thus, an urgent need exists to find ways to combat resistant pathogens. One promising approach to overcoming bacterial resistance is the use of herbal products. Green tea catechins, the major green tea polyphenols, show antimicrobial activity against resistant pathogens. The present study aimed to investigate the effect of catechins, green tea extract, and methylxanthines in combination with gentamicin against standard and clinical isolates of Staphylococcus aureus (S. aureus) and the standard strain of Pseudomonas aeruginosa (P. aeruginosa).

Methods:

The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) values of different agents against bacterial strains were determined. The interactions of green tea extract, epigallate catechin, epigallocatechin gallate, two types of methylxanthine, caffeine, and theophylline with gentamicin were studied in vitro by using a checkerboard method and calculating the fraction inhibitory concentration index (FICI).

Results:

The MICs of gentamicin against bacterial strains were in the range of 0.312 - 320 μg/mL. The MIC values of both types of catechins were 62.5 - 250 μg/ mL. Green tea extract showed insufficient antibacterial activity when used alone. Methylxanthines had no intrinsic inhibitory activity against any of the bacterial strains tested. When green tea extract and catechins were combined with gentamicin, the MIC values of gentamicin against the standard strains and a clinical isolate were reduced, and synergistic activities were observed (FICI < 1). A combination of caffeine with gentamicin did not alter the MIC values of gentamicin.

Conclusion:

The results of the present study revealed that green tea extract and catechins potentiated the antimicrobial action of gentamicin against some clinical isolates of S. aureus and standard P. aeruginosa strains. Therefore, combinations of gentamicin with these natural compounds might be a promising approach to combat microbial resistance.

Caffeine Administration to Prevent Apnea in Very Premature Infants

BACKGROUND

Apnea intervals frequently occur in premature infants. Periods of apnea occur more often with decreases in gestational age. Periods of apnea can cause damage to the infant's developing brain and other organs. This study was designed to investigate the preventive effects of caffeine on apnea incidence in higher-risk neonates.

METHODS

In this single-center randomized control trial study, premature infants with a birth weight of ≤1200 g were eligible for enrollment. Twenty-six infants were randomly assigned to receive 20 mg/kg caffeine, as the loading dose, which was followed by 5 mg/kg daily as the maintenance dose until the 10^th day of life; these infants were compared with 26 infants in the control group. Primary outcomes were incidence of apnea, bradycardia, and cyanosis.

RESULTS

Fifty-two infants were enrolled (26 in the caffeine group and 26 in the control group). The preventive effect of caffeine on apnea was significant in these infants. The relative risk for incidence of apnea in preterm neonates with a birth weight of <1200 g was 0.250 (95% confidence interval, 0.097-0.647). Only four infants (15.4%) in the caffeine group developed apnea, compared with 16 (61.5%) in the control group (p = 0.001).

CONCLUSION

It seems that preventative effects of caffeine on apnea become apparent by using the drug in very premature infants.

Structure-Bioactivity Relationships of Methylxanthines: Trying to Make Sense of All the Promises and the Drawbacks

Methylxanthines are a group of phytochemicals derived from the purine base xanthine and obtained from plant secondary metabolism. They are unobtrusively included in daily diet in common products as coffee, tea, energetic drinks, or chocolate. Caffeine is by far the most studied methylxanthine either in animal or epidemiologic studies. Theophylline and theobromine are other relevant methylxanthines also commonly available in the aforementioned sources. There are many disseminated myths about methylxanthines but there is increased scientific knowledge to discuss all the controversy and promise shown by these intriguing phytochemicals. In fact, many beneficial physiologic outcomes have been suggested for methylxanthines in areas as important and diverse as neurodegenerative and respiratory diseases, diabetes or cancer. However, there have always been toxicity concerns with methylxanthine (over)consumption and pharmacologic applications. Herein, we explore the structure-bioactivity relationships to bring light those enumerated effects. The potential shown by methylxanthines in such a wide range of conditions should substantiate many other scientific endeavors that may highlight their adequacy as adjuvant therapy agents and may contribute to the advent of functional foods. Newly designed targeted molecules based on methylxanthine structure may originate more specific and effective outcomes.

A Case Series of Clenbuterol Toxicity Caused by Adulterated Heroin

BACKGROUND

Adulteration of drugs of abuse may be done to increase profits. Some adulterants are relatively innocuous and others result in significant toxicity. Clenbuterol is a β2-adrenergic agonist with veterinary uses that has not been approved by the U.S. Food and Drug Administration for human use. It is an infrequently reported heroin adulterant. We describe a cluster of hospitalized patients with laboratory-confirmed clenbuterol exposure resulting in serious clinical effects.

CASE SERIES

Ten patients presented with unexpected symptoms shortly after heroin use. Seven evaluated by our medical toxicology service are summarized. Presenting symptoms included chest pain, dyspnea, palpitations, and nausea/vomiting. All patients were male, with a median age of 40 years (interquartile range [IQR] 38-46 years). Initial vital signs included a heart rate of 120 beats/min (IQR 91-137 beats/min), a respiratory rate of 20 breaths/min (IQR 18-22 breaths/min), a temperature of 36.8°C (IQR 36.7-37.0°C), a systolic blood pressure of 107 mm Hg (IQR 91-131 mm Hg), and a diastolic blood pressure of 49 mm Hg (IQR 40-70 mm Hg). Serum potassium nadir was 2.5 mEq/L (IQR 2.2-2.6 mEq/L), initial glucose was 179 mg/dL (IQR 125-231 mg/dL), initial lactate was 9.4 mmol/L (IQR 4.7-10.5 mmol/L), and peak creatine phosphokinase was 953 units/L (IQR 367-10,363 units/L). The median peak troponin level in six patients was 0.7 ng/mL (IQR 0.3-2.4 ng/mL). Three patients underwent cardiac catheterization and none had significant coronary artery disease. Clenbuterol was detected in all patients after comprehensive testing. All patients survived with supportive care. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Atypical presentations of illicit drug intoxication may raise concern for drug adulteration. In the case of heroin use, the presence of adrenergic symptoms or chest pain with hypokalemia, lactic acidosis, and hyperglycemia suggests adulteration with a β-agonist, such as clenbuterol, and patients presenting with these symptoms often require hospitalization.

Effects of infant flow Bi-NCPAP on apnea of prematurity

BACKGROUND

Infant flow biphasic nasal continuous positive airway pressure (Bi-NCPAP) and regular NCPAP (Re-NCPAP) are equally useful with respect to the rate of successful weaning from mechanical ventilation. It remains unclear, however, whether Bi-NCPAP or Re-NCPAP is more effective for reducing apnea of prematurity (AOP).

METHODS

A multicenter randomized controlled study was conducted of 66 infants assigned to receive Bi-NCPAP and 66 assigned to receive Re-NCPAP for respiratory support after extubation. Primary outcome was the number of AOP events during the 48 h observation period after successful extubation, defined as no reintubation and no adverse events associated with the use of NCPAP during the observation period. The secondary outcome was successful extubation. Reintubation was at the discretion of the attending physician.

RESULTS

Baseline characteristics were similar between the two groups. The number of AOP events during the 48 h observation period was significantly lower in infants with Bi-NCPAP than in those with Re-NCPAP (5.2 ± 6.5 vs 10.3 ± 10.9 per infant, respectively; P = 0.002). The rate of successful extubation tended to be greater in those with Bi-NCPAP than in those with Re-NCPAP (92.4%, 61/66 vs 80.3%, 53/66, respectively; P = 0.074). Adverse events occurred in only one of 132 infants: erosive dermatitis developed on the nose after application of Re-NCPAP. The risk of reintubation did not differ significantly between the two groups (7.6%, 5/66 for Bi-NCPAP vs 18.2%, 12/66 for Re-NCPAP; P = 0.117).

CONCLUSIONS

Bi-NCPAP was superior to Re-NCPAP for reduction of AOP following extubation.

Caffeine affects CD8+ lymphocyte apoptosis and migration differently in naïve and familiar individuals following moderate intensity exercise

The purpose of this investigation was to determine the lymphocyte subset response to 30 min of moderate treadmill exercise during caffeine supplemented (6.0 mg.kg(-1)) and placebo conditions in caffeine-naïve and -familiar individuals. Seventeen individuals participated (caffeine-familiar = 8, caffeine-naïve = 9) completing two exercise bouts (caffeine supplemented and placebo control) 48 h apart in a counterbalanced and double-blinded fashion. Individuals were classified as follows: caffeine-naive <50 mg.d(-1) and caffeine-familiar >200 mg.d(-1) Whole blood samples were obtained at rest, 30 min after caffeine or placebo ingestion, immediately following exercise, and 1 h post exercise. Blood was used to analyze apoptosis (annexin V) and cellular migration (CX3CR1) responses in lymphocyte subsets (CD4+, CD8+, CD19+). Absolute changes from rest values were calculated and differences between conditions were determined through Chi-squared analysis with significance accepted at P <0.05. With regard to CD4+ and CD19+ lymphocytes, the interaction of caffeine and exercise did not affect naïve individuals to a greater extent immediately post exercise when compared to familiar, as similar apoptotic and migratory responses were observed (P >0.05). However, CD8+ lymphocyte cell death and migration responses were observed to be significantly greater at each sampling point in caffeine-familiar individuals (P <0.05). It is possible that chronic caffeine supplementation may prime CD8+ cell receptors for responsiveness to apoptosis and migration and the consequence of this form of immunosuppression in the post-exercise period should be determined.

Effect of a high and low dose of caffeine on human lymphocyte activation in response to antigen stimulation

This study investigated the effect of caffeine on antigen-stimulated lymphocyte activation. Six males rested for 3.5 h after ingesting 0 (PLA), 2, or 6 (6CAF) mg·kg(-1) body mass of caffeine. The number of antigen-stimulated NK CD69(+) cells increased in 6CAF at 1 h compared with PLA (P = 0.021). Caffeine did not influence the number of antigen-stimulated CD69(+) T cells or the geometric mean fluorescence intensity expression of CD69 on antigen-stimulated lymphocytes, suggesting caffeine has little effect on antigen-stimulated lymphocyte activation.

A review of the use of adjunctive therapies in severe acute asthma exacerbation in critically ill children

Asthma is a common and potentially life threatening childhood condition. Asthma involves not only chronic airway remodeling, but may also include frequent exacerbations resulting from bronchospasm, edema, and mucus production. In children with severe exacerbations, standard therapy with β2-agonists, anti-cholinergic agents, oxygen, and systemic steroids may fail to reverse the severe airflow obstruction and necessitate use of adjunctive therapies. These therapies include intravenous or inhaled magnesium, inhaled helium-oxygen mixtures, intravenous methylxanthines, intravenous β2-agonists, and intravenous ketamine. Rarely, these measures are not successful and following the initiation of invasive mechanical ventilation, inhaled anesthetics or extracorporeal life support may be required. In this review, we discuss the mechanisms and evidence for adjunctive therapies in the setting of severe acute asthma exacerbations in children.

Theophylline

Theophylline (3-methyxanthine) has been used to treat airway diseases for over 70 years. It was originally used as a bronchodilator but the relatively high doses required are associated with frequent side effects, so its use declined as inhaled β₂-agonists became more widely used. More recently it has been shown to have anti-inflammatory effects in asthma and COPD at lower concentrations. The molecular mechanism of bronchodilatation is inhibition of phosphodiesterase(PDE)3 and PDE4, but the anti-inflammatory effect may be due to histone deacetylase (HDAC) activation, resulting in switching off of activated inflammatory genes. Through this mechanism theophylline also reverses corticosteroid resistance and this may be of particular value in severe asthma and COPD where HDAC2 activity is markedly reduced. Theophylline is given systemically (orally as slow-release preparations for chronic treatment and intravenously for acute exacerbations of asthma) and blood concentrations are determined mainly by hepatic metabolism, which may be increased or decreased in several diseases and by concomitant drug therapy. Theophylline is now usually used as an add-on therapy in asthma patients not well controlled on inhaled corticosteroids and in COPD patients with severe disease not controlled by bronchodilator therapy. Side effects are related to plasma concentrations and include nausea, vomiting and headaches due to PDE inhibition and at higher concentrations to cardiac arrhythmias and seizures due to adenosine A₁-receptor antagonism.

Autoradiographic localization of adenosine A1 receptors in rat brain using [3H]XCC, a functionalized congener of 1,3-dipropylxanthine

Quantitative autoradiography was used to visualize the anatomical distribution of adenosine receptors labeled by the carboxylic acid congener of 1,3-dipropylxanthine, [3H](8-(p-carboxymethyloxy)phenyl-1,3-dipropylxanthine)([3H]XCC ) in the rat brain. [3H]XCC was observed to specifically bind to rat brain sagittal sections in a heterogeneous pattern. Saturation experiments revealed that [3H]XCC binds with nanomolar affinity to 20-microns frozen tissue sections with the highest binding densities occurring in the hippocampus and cerebellum. Both the binding characteristics and regional receptor distribution obtained with [3H]XCC demonstrate the potential usefulness of this new ligand in the study of adenosine A1 receptors.

Stimulation of release of adrenal catecholamine by adenosine 3':5'-cyclic monophosphate and theophylline in the absence of extracellular Ca 2+

Stimulation of catecholamine release was studied in the isolated adrenal of the cat during retrograde perfusion. Theophylline, adenosine 3':5'-cyclic monophosphate (cyclic AMP), and dibutyryl-cyclic AMP stimulated catecholamine release in adrenal chromaffin tissue; adenosine, 2'-AMP, 3'-AMP, and 5'-AMP were ineffective. Addition of theophylline for 5-15 min had no effect on catecholamine release induced by KCl or nicotine, but it significantly increased the responses to cyclic AMP and its dibutyryl derivative. Glands perfused with Ca(2+)-free Locke's solution for 30-180 min rapidly lost their responsiveness to KCl or nicotine. In contrast, exposure to Ca(2+)-free medium for 180 min had no effect on secretory responses to either the cyclic nucleotides, themselves, or to methylxanthine-induced potentiation of cyclic AMP responses. Thus, dibutyryl-cyclic AMP, cyclic AMP, and theophylline do not require extracellular Ca(2+) to release adrenal catecholamines. They may act by translocating intracellular bound Ca(2+) or by a mechanism independent of calcium.