Severe 25E-NBOH intoxication associated with MDPHP intake: a case report, metabolism study, and literature review

N-Benzylphenethylamine derivatives are 5-HT2A receptor agonists with hallucinogenic properties, including NBOMe (N-(2-methoxybenzyl)-2-(3,4,5-trimethoxyphenyl)ethan-1-amine) and NBOH (2-(((2,5-dimethoxyphenethyl)amino)methyl)phenol). We reported here the case of a 23-year-old man who presented a serotoninergic syndrome and a loss of consciousness following the consumption of a powder labelled as 25I-NBOH. Toxicological analyses of biological samples were carried out using a liquid chromatography high-resolution mass spectrometry. Two new psychoactive substances were identified and confirmed with certified reference materials: 25E-NBOH (2-(((4-ethyl-2,5-dimethoxyphenethyl)amino)methyl)phenol) and MDPHP (1-(benzo[d][1,3]dioxol-5-yl)-2-(pyrrolidin-1-yl)hexan-1-one). Pharmaceuticals administered to the patient during his medical care were found in plasma and urine. 25E-NBOH and MDPHP concentrations were respectively at 2.3 ng/mL and 3.4 ng/mL in plasma, and 25.7 ng/mL and 30.5 ng/mL in urine. 25I-NBOH (2-(((4-iodo-2,5-dimethoxyphenethyl)amino)methyl)phenol) was specifically searched in both samples and was not detected. These results are discussed along with a literature review on human cases of exposure to N-benzylphenethylamine derivatives. Using molecular networking approach, we propose the first 25E-NBOH metabolism study using authentic biological samples (plasma and urine). We described seven metabolites (M1 to M7), including two phase I (m/z 330.172; m/z 288.160) and five phase II metabolites (m/z 464.191, m/z 478.207, m/z 492.223, m/z 508.218; m/z 396.156). The M6 (m/z 492.223) was the most intense ion detected in plasma and urine and could be proposed as a relevant 25E-NBOH consumption marker. Overall, we described an original case of 25E-NBOH poisoning and identified metabolites that could potentially be used as consumption markers to detect 25E-NBOH intoxications with a higher confidence level and probably a longer detection window.

Hair analysis in postmortem investigations: Case of a skeletonized body

Analysis of hair collected from putrefied or skeletal bodies is always complex and must take into account several pitfalls, such as external contamination and contamination by biological fluids. This work presents a case of particular complexity. A skeletonized body was discovered on a country road. A tuft of brown hair, detached from the scalp, irregular in length, non-oriented, in contact with soil and vegetation, was removed. An anthropological examination was carried out and genetic samples were taken from the right femoral shaft. After about 10 washes with warm water and dichloromethane, the tuft of hair was analyzed without segmentation. General unknown screening was performed by liquid chromatography system coupled to a high-resolution mass spectrometry (LC-HRMS) after incubation in pH 9.5 borate buffer and liquid-liquid extraction. Specific Multiple Reaction Monitoring (MRM) methods for date rape drugs were carried out by liquid chromatography system coupled to a tandem mass spectrometry (LC-MS/MS). The anthropological examination allowed to determine that the victim was a female individual, over 60 years old, the death dating from 3 months to 1 year. Comparison of the DNA results with the Missing Persons Index led to the identification, a 60-year-old woman who disappeared 5 months earlier. Hair analysis showed the presence of oxazepam (361 pg/mg), nordiazepam (54 pg/mg), and alimemazine (5 pg/mg). The interpretation of these concentrations is extremely difficult due to the risk of degradation of the hair cuticle during prolonged stay in the soil, as well as of contamination by putrefactive fluids. The authors discuss the value of using multiple biological and non-biological matrices in this context to improve the interpretation of the results.

Sexually Dimorphic Adolescent Trajectories of Prefrontal Endocannabinoid Synaptic Plasticity Equalize in Adulthood, Reflected by Endocannabinoid System Gene Expression

Introduction: How sex influences prefrontal cortexes (PFCs) synaptic development through adolescence remains unclear. Materials and Methods: In this study we describe sex-specific cellular and synaptic trajectories in the rat PFC from adolescence to adulthood. Results: The excitability of PFC layer 5 pyramidal neurons was lower in adult females compared with other developmental stages. The developmental course of endocannabinoid-mediated long-term depression (eCB-LTD) was sexually dimorphic, unlike long-term potentiation or mGluR3-LTD. eCB-LTD was expressed in juvenile females but appeared only at puberty in males. Endovanilloid TRPV1R or eCB receptors were engaged during LTD in a sequential and sexually dimorphic manner. Gene expression of the eCB/vanilloid systems was sequential and sex specific. LTD-incompetent juvenile males had elevated expression levels of the CB1R-interacting inhibitory protein cannabinoid receptor interacting protein 1a and of the 2-arachidonoylglycerol-degrading enzyme ABHD6. Pharmacological inhibition of ABHD6 or MAGL enabled LTD in young males, whereas inhibition of anandamide degradation was ineffective. Conclusions: These results reveal sex differences in the maturational trajectories of the rat PFC.

Validation of a non-targeted method devoted to identification and quantitation of toxicologically relevant compounds in plasma with HRMS

The objective of this study was to develop and validate a simple method using liquid chromatography hyphenated to high resolution mass spectrometry (HRMS) allowing both the performance of a non-targeted screening and the simultaneous quantification of 29 compounds of interest in clinical and forensic toxicology. Extraction was done with QuEChERS salts and acetonitrile, after addition of internal standard to 200 μL of human plasma samples. The mass spectrometer was an Orbitrap, with a heated electrospray ionization (HESI) probe. The analyses were carried out in full scan experiment with a nominal resolving power of 60,000 FWHM within the 125-650 m/z mass range, followed by four cycles of data dependent analysis (DDA) with a mass resolution of 16,000 FWHM. The untargeted screening was evaluated using 132 compounds, mean limit of identification (LOI) was 8.8 ng/mL (min = 0.05 ng/mL, max = 500 ng/mL) and mean limit of detection (LOD) was 0.25 ng/mL (min = 0.05 ng/mL, max = 5 ng/mL). The method was linear in the 5 to 500 ng/mL range (0.5 to 50 ng/mL for cannabinoids, 6-acetylmorphine and buprenorphine) with correlation coefficients > 0.99, intra- and inter-day accuracy and precision were < 15% for all compounds. The method was successfully applied to 31 routine samples.

Determination of cannabinoids content in light cannabis inflorescences sold in France

In the last 2 years, the number of shops selling CBD-rich THC-deprived cannabis flowers (CrTd) has increased considerably in France as in many European countries. The objective of this study was to determine the actual composition of the samples sold in these stores and to discuss regulatory consequences that may affect users. Samples were provided from shops in the region Provence-Alpes Cote d'Azur (PACA), France. Pictures of the samples were taken before they were weighed then crushed. Twenty milligrams were diluted in 10 ml heptane ethyl acetate (7:1; v:v) for analysis by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The method was validated according to SWGTOX guidelines for the quantification of cannabidiol (CBD), delta-9-tetrahydrocannabinol (THC) and cannabinol (CBN). Thirty-nine samples obtained between November 2021 and January 2022 in the PACA region were analyzed in this study. Mean content was 0.32% (0.03%-0.77%; STDV = 0.17%; n = 39) for THC, 2.23% (0.01%-5.97%; STDV = 1.29%; n = 39) for CBD and 0.01% (0.004%-0.025%; STDV = 0.01%; n = 19) for CBN. THC content over the threshold defined by the European legislation (>0.3%) was found in 18 of the 39 samples analyzed together with a CBD content <1% in nine samples (23%). None of the products analyzed had health risk messages on the packaging. The consumption of these products may lead to the presence of THC in biological fluids, which can be detected by screening. Users may then find themselves in breach of the law particularly when driving. Consumers should therefore be informed both about the actual composition of these products and about the legal and health risks they run.

Occurrence and severity of cocaine-induced hallucinations: Two distinct phenotypes with shared clinical factors but specific genetic risk factors

Cocaine-induced transient hallucinations (CIH) are a frequent complication following cocaine intake that is associated with addiction severity.

METHODS

Two hundred and forty-two non-psychotic and Caucasian lifetime cocaine users were included in a French multicentric study. Clinical variables and dopamine pathway genotype data were extracted and tested with CIH scores using a zero-inflated binomial model, which allows for the exploration of factors associated with occurrence and severity separately.

RESULTS

Cocaine dependence (p_occurrence= 6.18 × 10^-5, p_severity= 9.25 × 10^-8), number of cocaine dependence DSM IV-Tr criteria (p_occurrence= 1.22 × 10^-7, p_severity= 5.09 × 10^-6), and frequency of intake during the worst period of misuse (p_occurrence= 8.51 × 10^-04, p_severity= 0.04) were associated with greater occurrence and higher severity of CIH. The genetic associations did not yield significant results after correction for multiple tests. However, some nominal associations of SNPs mapped to the VMAT2, DBH, DRD1, and DRD2 genes were significant. In the multivariate model, the significant variables were the number of cocaine dependence criteria, lifetime alcohol dependence, and the nominally associated SNPs.

CONCLUSION

Our study shows that CIH occurrence and severity are two distinct phenotypes, with shared clinical risk factors; however, they likely do not share the same genetic background.

Childhood trauma and the severity of past suicide attempts in outpatients with cocaine use disorders

INTRODUCTION

Suicide attempts have been associated with both cocaine use disorder (CocUD) and childhood trauma. We investigated how childhood trauma is an independent risk factor for serious and recurrent suicide attempts in CocUD. Method: 298 outpatients (23% women) with CocUD underwent standardized assessments of substance dependence (Diagnostic and Statistical Manual-mental disorders, fourth edition, text revised), impulsiveness, resilience, and childhood trauma, using validated tools. Suicide attempts history was categorized as single vs. recurrent or non-serious vs. serious depending on the lifetime number of suicide attempts and the potential or actual lethality of the worst attempt reported, respectively. Bivariate and multinomial regression analyses were used to characterize which childhood trauma patterns were associated with the suicide attempts groups. Results: 58% of CocUD patients reported childhood trauma. Recurrent and serious suicide attempts clustered together and were thus combined into "severe SA." Severe suicide attempt risk increased proportionally to the number of childhood traumas (test for trend, p = 9 × 10^-7). Non-severe suicide attempt risk increased with impulsiveness and decreased with resilience. In multinomial regression models, a higher number of traumas and emotional abuse were independently and only associated with severe vs. non-severe suicide attempts (effect size = 0.82, AUC = 0.7). The study was limited by its cross-sectional design. Conclusion: These preferential associations between childhood trauma and severe suicide attempts warrant specific monitoring of suicide attempts risk in CocUD, regardless of the severity of addiction profiles.

Prenatal cannabinoid exposure alters the ovarian reserve in adult offspring of rats

In animals, research in the past two decades has demonstrated the strong involvement of the endocannabinoid system (ECS) in numerous steps of the reproductive process, including ovarian physiology. Reproductive lifespan is closely related to the number of nongrowing ovarian follicles, called ovarian reserve (OR), which is definitively established during foetal life. Thus, OR damage may lead to poor reproductive outcomes and a shortened reproductive lifespan. We investigated whether prenatal ECS modulation had an effect on the OR at different ages in the rat offspring. Four groups of gestating female rats (F0) were exposed to the CB1-/CB2-receptor agonist WIN55212 (0.5 mg/kg), the CB1R inverse agonist SR141716 (3 mg/kg) or Δ9THC (5 mg/kg) and were compared to negative control groups. OR was histologically assessed at different postnatal timepoints (F1 individuals): postnatal day (PND) 6, PND40 and PND90. At PND6, prenatal exposure had no effect on OR. In the young adult group (PND90) exposed during gestation to WIN55212, we observed a CB1R-mediated delayed OR decrease, which was reversed by prenatal CB1R blockade by SR141716. Conversely, after prenatal SR141716 exposure, we observed higher OR counts at PND90. RT-PCR experiments also showed that prenatal ECS modulation perturbed the mRNA levels of ECS enzymes and OR regulation genes. Our findings support the role of the ECS in OR regulation during the foetal life of rats and highlight the need for further studies to elucidate its precise role in OR physiology.

Cannabinoid Exposure via Lactation in Rats Disrupts Perinatal Programming of the Gamma-Aminobutyric Acid Trajectory and Select Early-Life Behaviors

BACKGROUND

Cannabis usage is increasing with its widespread legalization. Cannabis use by mothers during lactation transfers active cannabinoids to the developing offspring during this critical period and alters postnatal neurodevelopment. A key neurodevelopmental landmark is the excitatory to inhibitory gamma-aminobutyric acid (GABA) switch caused by reciprocal changes in expression ratios of the K+/Cl- transporters potassium-chloride cotransporter 2 (KCC2) and sodium-potassium-chloride transporter (NKCC1).

METHODS

Rat dams were treated with Δ9-tetrahydrocannabinol or a synthetic cannabinoid during the first 10 days of postnatal development, and experiments were then conducted in the offspring exposed to these drugs via lactation. The network influence of GABA transmission was analyzed using cell-attached recordings. KCC2 and NKCC1 levels were determined using Western blot and quantitative polymerase chain reaction analyses. Ultrasonic vocalization and homing behavioral experiments were carried out at relevant time points.

RESULTS

Treating rat dams with cannabinoids during early lactation retards transcriptional upregulation and expression of KCC2, thereby delaying the GABA switch in pups of both sexes. This perturbed trajectory was corrected by the NKCC1 antagonist bumetanide and accompanied by alterations in ultrasonic vocalization without changes in homing behavior. Neurobehavioral deficits were prevented by CB1 receptor antagonism during maternal exposure, showing that the CB1 receptor underlies the cannabinoid-induced alterations.

CONCLUSIONS

These results reveal how perinatal cannabinoid exposure retards an early milestone of development, delaying the trajectory of GABA's polarity transition and altering early-life communication.

Post Mortem Redistribution of Drugs: Current State of Knowledge

BACKGROUND

Drug concentrations obtained from post mortem samples do not necessarily reflect the concentrations at the time of death, and variations of concentration may be observed between different sites and/or different sampling times. These phenomena, collectively termed post mortem redistribution, concern numerous molecules (medications, drugs of abuse, gases, etc.) and can complicate the interpretation of toxicological analyses.

METHODS

Literature review.

RESULTS

The mechanisms that cause these phenomena are complex and often intricate. Certain organs, which concentrate the molecules before death, may release them very early in the vascular sector. The gastrointestinal tract, liver, lungs and myocardium are mainly concerned. Cell autolysis also plays a part in drug release. Furthermore, micro-organisms (mainly bacteria and yeasts) which colonize the organism during putrefaction may cause neoformation and/or the degradation of certain molecules. Lastly, it appears that the physicochemical and pharmacokinetic profile of xenobiotics, notably their lipophilic nature, their ionization state and their volume of distribution may be factors likely to influence redistribution phenomena. Some recommendations concerning anatomic sampling sites, sampling methods and sample storage make it possible to limit these phenomena.

Sex Differences in the Behavioral and Synaptic Consequences of a Single in vivo Exposure to the Synthetic Cannabimimetic WIN55,212-2 at Puberty and Adulthood

Heavy cannabis consumption among adolescents is associated with significant and lasting neurobiological, psychological and health consequences that depend on the age of first use. Chronic exposure to cannabinoid agonists during the perinatal period or adolescence alters social behavior and prefrontal cortex (PFC) activity in adult rats. However, sex differences on social behavior as well as PFC synaptic plasticity after acute cannabinoid activation remain poorly explored. Here, we determined that the consequences of a single in vivo exposure to the synthetic cannabimimetic WIN55,212-2 differently affected PFC neuronal and synaptic functions after 24 h in male and female rats during the pubertal and adulthood periods. During puberty, single cannabinoid exposure (SCE) reduced play behavior in females but not males. In contrast, the same treatment impaired sociability in both sexes at adulthood. General exploration and memory recognition remained normal at both ages and both sexes. At the synaptic level, SCE ablated endocannabinoid-mediated synaptic plasticity in the PFC of females of both ages and heightened excitability of PFC pyramidal neurons at adulthood, while males were spared. In contrast, cannabinoid exposure was associated with impaired long-term potentiation (LTP) specifically in adult males. Together, these data indicate behavioral and synaptic sex differences in response to a single in vivo exposure to cannabinoid at puberty and adulthood.

Sex-dependent effects of in utero cannabinoid exposure on cortical function

Cannabinoids can cross the placenta, thus may interfere with fetal endocannabinoid signaling during neurodevelopment, causing long-lasting deficits. Despite increasing reports of cannabis consumption during pregnancy, the protracted consequences of prenatal cannabinoid exposure (PCE) remain incompletely understood. Here, we report sex-specific differences in behavioral and neuronal deficits in the adult progeny of rat dams exposed to low doses of cannabinoids during gestation. In males, PCE reduced social interaction, ablated endocannabinoid long-term depression (LTD) and heightened excitability of prefrontal cortex pyramidal neurons, while females were spared. Group 1 mGluR and endocannabinoid signaling regulate emotional behavior and synaptic plasticity. Notably, sex-differences following PCE included levels of mGluR1/5 and TRPV1R mRNA. Finally, positive allosteric modulation of mGlu5 and enhancement of anandamide levels restored LTD and social interaction in PCE adult males. Together, these results highlight marked sexual differences in the effects of PCE and introduce strategies for reversing detrimental effects of PCE.

Endocannabinoids Mediate Muscarinic Acetylcholine Receptor-Dependent Long-Term Depression in the Adult Medial Prefrontal Cortex

Cholinergic inputs into the prefrontal cortex (PFC) are associated with attention and cognition; however there is evidence that acetylcholine also has a role in PFC dependent learning and memory. Muscarinic acetylcholine receptors (mAChR) in the PFC can induce synaptic plasticity, but the underlying mechanisms remain either opaque or unresolved. We have characterized a form of mAChR mediated long-term depression (LTD) at glutamatergic synapses of layer 5 principal neurons in the adult medial PFC. This mAChR LTD is induced with the mAChR agonist carbachol and inhibited by selective M₁ mAChR antagonists. In contrast to other cortical regions, we find that this M₁ mAChR mediated LTD is coupled to endogenous cannabinoid (eCB) signaling. Inhibition of the principal eCB CB₁ receptor blocked carbachol induced LTD in both rats and mice. Furthermore, when challenged with a sub-threshold carbachol application, LTD was induced in slices pretreated with the monoacylglycerol lipase (MAGL) inhibitor JZL184, suggesting that the eCB 2-arachidonylglyerol (2-AG) mediates M₁ mAChR LTD. Yet, when endogenous acetylcholine was released from local cholinergic afferents in the PFC using optogenetics, it failed to trigger eCB-LTD. However coupling patterned optical and electrical stimulation to generate local synaptic signaling allowed the reliable induction of LTD. The light—electrical pairing induced LTD was M₁ mAChR and CB₁ receptor mediated. This shows for the first time that connecting excitatory synaptic activity with coincident endogenously released acetylcholine controls synaptic gain via eCB signaling. Together these results shed new light on the mechanisms of synaptic plasticity in the adult PFC and expand on the actions of endogenous cholinergic signaling.

Childhood trauma are not associated with the intensity of transient cocaine induced psychotic symptoms

A personal history of childhood trauma has been associated with the severity of psychotic symptoms in several disorders. We evaluated retrospectively cocaine-induced psychotic symptoms with the SAPS-CIP and childhood trauma with the CTQ in a clinical sample of 144 cocaine users. The SAPS-CIP score was not statistically associated with the presence or number or intensity of trauma, but was associated with rapid routes of administration (intravenous and smoked) and with frequent cocaine use.

Off-Label Prescribing by Psychiatrists: What is the Practitioner's Liability?

In psychiatry, the molecules available and the dosages recommended when a drug receives marketing authorization are not always adequate to treat patients with major behavioral disturbances. Off-label prescribing is frequent in this context, with regard to the indications and the dosages given as well as to the drug combinations used. However, if complications or death occur, the practitioner's liability may be engaged. The authors report three deaths attributed to off-label prescribing in psychiatry and which led to charges against the physicians. They review the precautions to be taken when prescribing in such conditions (no other possible treatment, existence of sound scientific evidence, consent obtained from the patient, or their legal representatives except in cases of force majeure) and the physician's liability if adverse events occur that could be attributed to off-label prescribing.

Can subclavian blood be equated with a peripheral blood sample? A series of 50 cases

If femoral blood is not available at autopsy, toxicological analyses, in particular blood ethanol measurements, are carried out on cardiac blood. This is known to be subject to major redistribution. We aimed to determine whether subclavian blood can be equated with a peripheral blood sample and could be used if femoral blood is not available. The study was based on 50 medicolegal autopsies in which we compared ethanol concentrations between subclavian blood, the different heart blood compartments (right and left cardiac blood), and femoral blood. Mechanisms that could lead to variations in concentration, i.e., postmortem redistribution and/or endogenous production, were also taken into account in interpreting the results. Ethanol concentrations were determined by headspace gas chromatography with a flame ionization detector. In each case, we recorded the circumstances of death, resuscitation attempts if any, degree of putrefaction, chest or abdominal trauma, and/or inhalation of gastric fluid in the airways. Ethanol concentrations in subclavian blood were found to be close to those in peripheral blood (p = 0.948) and were not influenced by the degree of putrefaction (r = 0.017, p = 0.904), gastric ethanol concentration (r = -0.011, p = 0.940), inhalation of gastric contents in the airways (p = 0.461), or cardiac resuscitation attempts (p = 0.368). We discuss the possible explanations for these findings and stress the value of sampling subclavian blood when femoral blood is not obtainable at autopsy.

The court medical expert in France: changes in status

In France the status of the court expert has undergone a significant change with the adoption of statute no. 2004-130 of 11 February 2004 and its implementing regulations no. 2004-1463 of 23 December 2004. This article looks at the two most outstanding aspects of this change in status: (i) the conditions for registering on a court of appeal list and, (ii) the practical details of the quality control of the court expert's work as exercised by the judge. The article concludes with a brief comparison with the expert witness situation in England and Wales.

Malnutrition, a Rare Form of Child Abuse: Diagnostic Criteria

Infantile malnutrition is often difficult to diagnose as it is rarely observed in industrialized countries. It may be associated with physical violence or occur in isolation. The essential clinical sign is height and weight retardation, but malnutrition also causes a variety of internal and bone lesions, which lead to neuropsychological sequelae and death. We report a rare case of death by malnutrition in a female child aged 6 1/2 months. The infant presented height and weight growth retardation and internal lesions related to prolonged protein-energy malnutrition (fat and muscle wasting, thymic atrophy, liver steatosis) resulting in a picture of marasmus or kwashiorkor. We detail the positive and negative criteria that established the diagnosis of abuse, whereas the parents had claimed a simple dietary error.

The regional commission for medical accidents and nosocomial infections set up by French law

The regional commission for conciliation and compensation for medical accidents, iatrogenic diseases and nosocomial infections (commission régionale de conciliation et d'indemnisation des accidents médicaux, affections iatrogènes et infections nosocomiales, CRCI) offers victims of such events the possibility of obtaining compensation without recourse to legal proceedings. We suggest various points of view about this commission set up by the French law no. 2002-303 of 4 March 2002: the composition, role and competence of the CRCI; the place of the expert's report; the opinion pronounced by the CRCI and its outcome, the compensation of victims and, finally, interaction with other procedures.

Comparison of ethanol concentrations in right cardiac blood, left cardiac blood and peripheral blood in a series of 30 cases

The aim of this study was to compare ethanol concentrations in right cardiac blood, left cardiac blood and peripheral blood. Samples were taken from a series of 30 medicolegal autopsies. Ethanol was measured by headspace GC-FID. In each case, the degree of putrefaction, chest or abdominal injury, and/or regurgitation of gastric contents into the airways were noted. Our results show that there exists in certain cases a marked increase in ethanol concentration in left cardiac blood compared with right cardiac blood and peripheral blood. In these cases, we observed (i) a high concentration of ethanol in the gastric contents and (ii) regurgitation of gastric contents into the airways. The authors discuss the post-mortem redistribution mechanisms which could explain these results and stress the value of sampling right cardiac blood at autopsy.

Time-of-day dependent pharmacodynamic and pharmacokinetic profiles of caffeine in rats

This study aims to investigate the effects of caffeine on the daily rhythms of heart rate (HR), body temperature (BT) and locomotor activity (LA) in rats in relation to time-of-day of administration, as well as their possible mechanisms, particularly related to caffeine pharmacokinetics. During the pharmacodynamic study, HR, BT and LA were measured every 10 min by radiotelemetry and analysed by Cosinor. This study was divided into three periods: a control period P1, a treatment period P2 and a recovery period P3. During P2, rats of the morning group ( M(tel)) received a 25 mg/kg s.c. dose of caffeine at 08.00 while rats of the evening group ( E(tel)) received the same dose of caffeine at 20.00. The pharmacokinetic study was conducted in parallel with the telemetric study and was divided into two periods: a control period P1, and a treatment period P2. During P2, animals of the morning ( M(pk)) and the evening ( E(pk)) groups received the same treatment as the animals of the telemetric study. At the last day of P2, blood samples were drawn 0.25, 0.5, 1, 2, 4, 8, 12 and 24 h after the last morning and the last evening administration in order to determine the pharmacokinetics of M(pk) and E(pk). Our results showed that morning administration of caffeine suppressed the daily rhythmicity of LA and modified the mesors and amplitudes of the HR and BT daily rhythms, while the evening administration did not suppress the daily rhythm of LA, but altered the mesors, amplitudes and acrophases of the three rhythms, indicating a chronopharmacological effect. With respect to the pharmacokinetic effects, the area under the curve (AUC) was significantly lower in rats of E(pk) compared with M(pk), due to an increase of the total plasma clearance and the volume of distribution. Our data suggest that the chronopharmacokinetic effects of caffeine may explain, at least in part, the observed caffeine-induced modifications on the daily rhythms.