PharmGKB summary: methylphenidate pathway, pharmacokinetics/pharmacodynamics

Human Data on Pharmacokinetic Interactions of Cannabinoids: A Narrative Review

Concomitant use of cannabinoids with other drugs may result in pharmacokinetic drug-drug interactions, mainly due to the mechanism involving Phase I and Phase II enzymes and/or efflux transporters. Cannabinoids are not only substrates but also inhibitors or inducers of some of these enzymes and/or transporters. This narrative review aims to provide the available information reported in the literature regarding human data on the pharmacokinetic interactions of cannabinoids with other medications. A search on Pubmed/Medline, Google Scholar, and Cochrane Library was performed. Some studies were identified with Google search. Additional articles of interest were obtained through cross-referencing of published literature. All original research papers discussing interactions between cannabinoids, used for medical or recreational/adult-use purposes, and other medications in humans were included. Thirty-two studies with medicinal or recreational/adult-use cannabis were identified (seventeen case reports/series, thirteen clinical trials, and two retrospective analyses). In three of these studies, a bidirectional pharmacokinetic drug-drug interaction was reported. In the rest of the studies, cannabinoids were the perpetrators, as in most of them, concentrations of cannabinoids were not measured. In light of the widespread use of prescribed and non-prescribed cannabinoids with other medications, pharmacokinetic interactions are likely to occur. Physicians should be aware of these potential interactions and closely monitor drug levels and/or responses. The existing literature regarding pharmacokinetic interactions is limited, and for some drugs, studies have relatively small cohorts or are only case reports. Therefore, there is a need for high-quality pharmacological studies on cannabinoid-drug interactions.

The effects of methylphenidate and atomoxetine on Drosophila brain at single-cell resolution and potential drug repurposing for ADHD treatment

The stimulant methylphenidate (MPH) and the non-stimulant atomoxetine (ATX) are frequently used for the treatment of attention-deficit/hyperactivity disorder (ADHD); however, the function of these drugs in different types of brain cells and their effects on related genes remain largely unknown. To address these questions, we built a pipeline for the simultaneous examination of the activity behavior and transcriptional responses of Drosophila melanogaster at single-cell resolution following drug treatment. We selected the Drosophila with significantly increased locomotor activities (hyperactivity-like behavior) following the administration of each drug in comparison with the control (same food as the drug-treated groups with 5% sucrose, yeast, and blue food dye solution) using EasyFlyTracker. Subsequently, single cell RNA sequencing (scRNASEQ) was used to capture the transcriptome of 82,917 cells, unsupervised clustering analysis of which yielded 28 primary cell clusters representing the major cell types in adult Drosophila brain. Indeed, both neuronal and glial cells responded to MPH and ATX. Further analysis of differentially expressed genes (DEGs) revealed distinct transcriptional changes associated with these two drugs, such as two well-studied dopamine receptor genes (Dop2R and DopEcR) were responsive to MPH but not to ATX at their optimal doses, in addition to genes involved in dopamine metabolism pathways such as Syt1, Sytalpha, Syt7, and Ih in different cell types. More importantly, MPH also suppressed the expression of genes encoding other neurotransmitter receptors and synaptic signaling molecules in many cell types, especially those for Glu and GABA, while the responsive effects of ATX were much weaker. In addition to monoaminergic neuronal transmitters, other neurotransmitters have also shown a similar pattern with respect to a stronger effect associated with MPH than with ATX. Moreover, we identified four distinct glial cell subtypes responsive to the two drugs and detected a greater number of differentially expressed genes associated with ensheathing and astrocyte-like glia. Furthermore, our study provides a rich resource of candidate target genes, supported by drug set enrichment analysis (P = 2.10E-4; hypergeometric test), for the further exploration of drug repurposing. The whole list of candidates can be found at ADHDrug ( http://adhdrug.cibr.ac.cn/ ). In conclusion, we propose a fast and cost-efficient pipeline to explore the underlying molecular mechanisms of ADHD drug treatment in Drosophila brain at single-cell resolution, which may further facilitate drug repurposing applications.

Methylphenidate induces a different response in the dorsal raphe as compared to ventral tegmental area and locus coeruleus: behavioral and concomitant neuronal recordings in adult rats

Methylphenidate (MPD) is a psychostimulant used to treat attention deficit hyperactivity disorder. MPD exerts its neurocognitive effects through increasing concentrations of dopamine (DA), norepinephrine (NE), and serotonin (5-HT) in the neuronal synapse. This study recorded from adult freely behaving rats a total of 1170 neurons, 403 from the ventral tegmental area (VTA), 409 from locus coeruleus (LC), and 356 from dorsal raphe (DR) nucleus, which are the main sources of DA, NE, and 5-HT to the mesocorticolimbic circuitry, respectively. Electrophysiological and behavioral activities were recorded simultaneously following acute and repetitive (chronic) saline or 0.6, 2.5, or 10.0 mg/kg MPD. The uniqueness of this study is the evaluation of neuronal activity based on the behavioral response to chronic MPD. Animals received daily saline or MPD administration on experimental days 1-6 (ED1-6), followed by a 3-day wash-out period, and then MPD rechallenge on ED10. Each chronic MPD dose elicits behavioral sensitization in some animals, while in others, behavioral tolerance. Neuronal excitation following chronic MPD was observed in brains areas of animals exhibiting behavioral sensitization, while neuronal attenuation following chronic MPD was observed in those animals expressing behavioral tolerance. DR neuronal activity was most affected in response to acute and chronic MPD administration and responded differently compared to the neurons recorded from VTA and LC neurons at all doses. This suggests that although not directly related, DR and 5-HT are involved in the acute and chronic effects of MPD in adult rats, but exhibit a different role in response to MPD.

Mechanisms of action underlying Shentong Zhuyu decoction based treatment of rheumatoid arthritis using systems biology and computer-aided drug design

Rheumatoid arthritis is an autoimmune disease characterized by chronic polyarticular pain, for which no cure currently exists. In Chinese medicine, rheumatoid arthritis (RA) is believed to be caused by phlegm and blood stagnation. Shentong Zhuyu decoction can be used to treat RA, as it promotes blood circulation, resolves blood stasis, and relieves pain. In our study, we used network pharmacology and computer-aided drug design to evaluate the components, active compounds, and targets of Shentong Zhuyu decoction (STZY). Our results suggest that STZY contains active compounds such as quercetin, luteolin, and formononetin that regulate immune network targets. RA associated genes are enriched in pathways including those associated with nuclear factor kappa B, phosphatidylinositol-3-kinase/AKT, and hypoxia inducible factor 1 signaling. The main active compounds in STZY (quercetin and luteolin) were derived from Achyranthis Bidentatae Radix, Carthami Flos, licorice, Cyperi Rhizoma, and Myrrha and targeted the pro-inflammatory cytokines interleukin 2, interleukin 1 alpha, interleukin 1 beta, and interleukin 6. In addition, the compounds quercetin, luteolin, and formononetin in these herbs can target the anti-inflammatory cytokines interleukin 4 and interleukin 10. Our results suggest that STZY can balance the immune network, promote an anti-inflammatory environment, and reduce the clinical symptoms of RA. Based on the close relationship between inflammatory response and osteoclast formation, we hypothesized that STZY may inhibit inflammation and alleviate bone destruction in RA. Our findings indicate that STZY can treat RA through multiple components, targets, and pathways. This study may provide a reference for the clinical application of STZY in RA treatment.

Dopamine, Norepinephrine and Serotonin Participate Differently in Methylphenidate Action in Concomitant Behavioral and Ventral Tegmental Area, Locus Coeruleus and Dorsal Raphe Neuronal Study in Young Rats

Methylphenidate (MPD), known as Ritalin, is a psychostimulant used to treat children, adults, and the elderly. MPD exerts its effects through increasing concentrations of dopamine (DA), norepinephrine (NE), and serotonin (5-HT) in the synaptic cleft. Concomitant behavioral and neuronal recording from the ventral tegmental area (VTA), locus coeruleus (LC), and from the dorsal raphe (DR) nucleus, which are the sources of DA, NE, and 5-HT to the mesocorticolimbic circuit, were investigated following acute and repetitive (chronic) saline, 0.6, 2.5, or 10.0 mg/kg MPD. Animals received daily saline or MPD administration on experimental days 1 to 6 (ED1-6), followed by a 3-day washout period and MPD rechallenge on ED10. Each chronic MPD dose elicits behavioral sensitization in some animals while inducing behavioral tolerance in others. The uniqueness of this study is in the evaluation of neuronal activity based on the behavioral response to chronic MPD. Neuronal excitation was observed mainly in brain areas of animals exhibiting behavioral sensitization, while neuronal attenuation following chronic MPD was observed in animals expressing behavioral tolerance. Different ratios of excitatory/inhibitory neuronal responses were obtained from the VTA, LC, or DR following chronic MPD. Thus, each brain area responds differently to each MPD dose used, suggesting that DA, NE, and 5-HT in the VTA, LC, and DR exert different effects.

In silico clinical trial evaluating lisdexamfetamine's and methylphenidate's mechanism of action computational models in an attention-deficit/hyperactivity disorder virtual patients' population

Introduction

Attention-deficit/hyperactivity disorder (ADHD) is an impairing psychiatric condition with the stimulants, lisdexamfetamine (LDX), and methylphenidate (MPH), as the first lines pharmacological treatment.

Methods

Herein, we applied a novel in silico method to evaluate virtual LDX (vLDX) and vMPH as treatments for ADHD applying quantitative systems pharmacology (QSP) models. The objectives were to evaluate the model's output, considering the model characteristics and the information used to build them, to compare both virtual drugs' efficacy mechanisms, and to assess how demographic (age, body mass index, and sex) and clinical characteristics may affect vLDX's and vMPH's relative efficacies.

Results and Discussion

We molecularly characterized the drugs and pathologies based on a bibliographic search, and generated virtual populations of adults and children-adolescents totaling 2,600 individuals. For each virtual patient and virtual drug, we created physiologically based pharmacokinetic and QSP models applying the systems biology-based Therapeutic Performance Mapping System technology. The resulting models' predicted protein activity indicated that both virtual drugs modulated ADHD through similar mechanisms, albeit with some differences. vMPH induced several general synaptic, neurotransmitter, and nerve impulse-related processes, whereas vLDX seemed to modulate neural processes more specific to ADHD, such as GABAergic inhibitory synapses and regulation of the reward system. While both drugs' models were linked to an effect over neuroinflammation and altered neural viability, vLDX had a significant impact on neurotransmitter imbalance and vMPH on circadian system deregulation. Among demographic characteristics, age and body mass index affected the efficacy of both virtual treatments, although the effect was more marked for vLDX. Regarding comorbidities, only depression negatively impacted both virtual drugs' efficacy mechanisms and, while that of vLDX were more affected by the co-treatment of tic disorders, the efficacy mechanisms of vMPH were disturbed by wide-spectrum psychiatric drugs. Our in silico results suggested that both drugs could have similar efficacy mechanisms as ADHD treatment in adult and pediatric populations and allowed raising hypotheses for their differential impact in specific patient groups, although these results require prospective validation for clinical translatability.

Uncovering the molecular mechanisms of Curcumae Rhizoma against myocardial fibrosis using network pharmacology and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Myocardial fibrosis leads to cardiac remodeling and dysfunction. Curcumae Rhizoma has been utilized in clinical trials to treat a variety of cardiovascular illnesses, although its role in myocardial fibrosis is unknown.

AIM OF THE STUDY

The purpose of current study was to explore the potential mechanism action and anti-myocardial fibrosis effects of treatment with Curcumae Rhizoma.

MATERIALS AND METHODS

The chemical components in the aqueous extract from Curcumae Rhizoma were identified using GC-MS analysis. A prediction network describing the relationship between Curcumae Rhizoma and MF was established based on information collected from multiple databases. Functional enrichment analysis was performed to investigate the specific functions and pathways involved in the candidate Curcumae Rhizoma targets acting on MF, which were further validated by vivo experiments.

RESULTS

There were 444 targets obtained from the 39 active ingredients in Curcumae Rhizoma, and 5691 disease targets related to MF were identified. Then, 41 key targets were determined with the PPI interaction network, which was structured from 324 overlapping gene targets. GO and KEGG analyses revealed that the p38 MAPK/NF-κB and TGF-β1/Smad2/3 signaling pathways might play crucial roles in the therapeutic mechanism of MF. According to the results of molecular docking, the binding activity between core components and targets was marvelous (affinity < -6 kcal/mol). Take it a step further, the experimental validation data affirmed that Curcumae Rhizoma substantially decreased myocardial fibrosis and recovered cardiac function in the ISO-induced rats. The associated proteins expression data implied that the p38 MAPK/NF-κB and TGF-β1/Smad2/3 pathways might be vital in the anti-fibrosis effect of Curcumae Rhizoma.

CONCLUSION

The findings suggested that Curcumae Rhizoma diminished myocardial fibrosis by suppressing fibrosis multiplication and collagen deposition through inhibiting p38 MAPK/NF-κB and TGF-β1/Smad2/3 pathways, which might be a promising therapeutic medicament for alleviating myocardial fibrosis.

Pharmacological and Physiological Correlates of the Bidirectional Fear Phenotype of the Carioca Rats and Other Bidirectionally Selected Lines

The Carioca rat lines originated from the selective bidirectional breeding of mates displaying extreme defense responses to contextual conditioned fear. After three generations, two distinct populations could be distinguished: the Carioca High- and Low-conditioned Freezing rats, CHF, and CLF, respectively. Later studies identified strong anxiety-like behaviors in the CHF line, while indications of impulsivity and hyperactivity were prominent in the CLF animals. The present review details the physiological and pharmacological-related findings obtained from these lines. The results discussed here point towards a dysfunctional fear circuitry in CHF rats, including alterations in key brain structures and the serotoninergic system. Moreover, data from these animals highlight important alterations in the stress-processing machinery and its associated systems, such as energy metabolism and antioxidative defense. Finally, evidence of an alteration in the dopaminergic pathway in CLF rats is also debated. Thus, accumulating data gathered over the years, place the Carioca lines as significant animal models for the study of psychiatric disorders, especially fear-related ones like anxiety.

The Pharmacokinetics and Pharmacogenomics of Psychostimulants

The psychostimulants-amphetamine and methylphenidate-have been in clinical use for well more than 60 years. In general, both stimulants are rapidly absorbed with relatively poor bioavailability and short half-lives. The pharmacokinetics of both stimulants are generally linear and dose proportional although substantial interindividual variability in pharmacokinetics is in evidence. Amphetamine (AMP) is highly metabolized by several oxidative enzymes forming multiple metabolites while methylphenidate (MPH) is primarily metabolized by hydrolysis to the inactive metabolite ritalinic acid. At present, pharmacogenomic testing as an aid to guide dosing and personalized treatment cannot be recommended for either agent. Few pharmacokinetically based drug-drug interactions (DDIs) have been documented for either stimulant.

The Pharmacogenetic Impact on the Pharmacokinetics of ADHD Medications

ADHD is a common condition in both children and adults. The most prescribed medications for the treatment of ADHD include methylphenidate, mixed amphetamine salts, atomoxetine, guanfacine, and clonidine. While each of these medications have their own distinct pharmacokinetic profile, the extent to which pharmacogenetics effects their pharmacokinetic parameters is best described in atomoxetine, followed by methylphenidate. Atomoxetine is predominantly metabolized by cytochrome p450 2D6 (CYP2D6), while methylphenidate is metabolized by carboxylesterase 1 (CES1). Both CYP2D6 and CES1 have multiple variants resulting in varying levels of enzyme activity; however, to date, the functional consequence of variants and alleles for CYP2D6 is better characterized as compared to CES1. Regarding CYP2D6, individuals who are poor metabolizers prescribed atomoxetine experience up to ten-fold higher exposure as compared to normal metabolizers at comparable dosing. Additionally, individuals prescribed methylphenidate with the rs71647871 variant may experience up to 2.5-fold higher exposure as compared to those without. Having this pharmacogenetic information available may aid clinicians and patients when choosing medications and doses to treat ADHD.

Associations between CES1 variants and dosing and adverse effects in children taking methylphenidate

BACKGROUND

Methylphenidate is the most prescribed stimulant to treat attention deficit-hyperactivity disorder (ADHD). Despite its widespread usage, a fair proportion of children are classified as non-responders to the medication. Variability in response and occurrence of adverse events with methylphenidate use may be due to several factors, including drug-drug interactions as well as pharmacogenetic differences resulting in pharmacokinetic and/or pharmacodynamic variances within the general population. The objective of this study was to analyze the effect of carboxylesterase 1 (CES1) variants on the frequency of adverse effects and dosing requirements of methylphenidate in children with ADHD.

METHODS

This was a retrospective cohort study of children and adolescents who met the inclusion criteria and had a routine visit during the enrollment period were invited to participate. Inclusion criteria included: ADHD diagnosis by a healthcare provider, between 6 and 16 years of age at the time of permission/assent, had not previously been prescribed methylphenidate, and treatment with any methylphenidate formulation for at least three consecutive months. Three months of records were reviewed in order to assess changes in dose and frequency of discontinuing methylphenidate. Participants' ADHD symptoms, medication response, adverse effects, select vitals, and dose were extracted from the electronic health record. Saliva samples were collected by trained study coordinators. Haplotypes were assigned based on copy number in different portions of the CES1 gene. Due to limited numbers, diplotypes (combinations of two haplotypes) were grouped for analysis as CES1A1/CES1A1, CES1A1/CES1A1c and CES1A1c/CES1A1c.

RESULTS

A total of 99 participants (n = 30 female; n = 69 male) had both clinical data and CES1 sequencing data, with an average age of 7.7 years old (range 3-15 years). The final weight-based dose in all individuals was 0.79 mg/kg/day. The most common adverse effects reported were decreased appetite (n = 47), weight loss (n = 24), and sleep problems (n = 19). The mean final weight-based dose by haplotype was 0.92 mg/kg for CES1A2/CES1A2, 0.81 mg/kg for CES1A2/CES1P1, and 0.78 mg/kg for CES1P1/CES1P1. After correction for multiple hypothesis testing, only one SNV, rs114119971, was significantly associated with weight-based dosing in two individuals. The individuals with the rs114119971 SNV had a significantly lower weight-based dose (0.42 mg/kg) as compared to those without (0.88 mg/kg; p < 0.001).

DISCUSSION

Variation in CES1 activity may impact dose requirements in children who are prescribed methylphenidate, as well as other CES1 substrates. Although intriguing, this study is limited by the retrospective nature and relatively small sample size.

Haloperidol and methylphenidate alter motor behavior and responses to conditioned fear of Carioca Low-conditioned Freezing rats

Animal models are important tools for studying neuropsychological disorders. Considering their limitations, a more extensive translational research must encompass data that are generated from several models. Therefore, a comprehensive characterization of these models is needed in terms of behavior and neurophysiology. The present study evaluated the behavioral responses of Carioca Low-conditioned Freezing (CLF) rats to haloperidol and methylphenidate. The CLF breeding line is characterized by low freezing defensive responses to contextual cues that are associated with aversive stimuli. CLF rats exhibited a delayed response to haloperidol at lower doses, needing higher doses to reach similar levels of catatonia as control randomly bred animals. Methylphenidate increased freezing responses to conditioned fear and induced motor effects in the open field. Thus, CLF rats differ from controls in their responses to both haloperidol and methylphenidate. Because of the dopamine-related molecular targets of these drugs, we hypothesize that dopaminergic alterations related to those of animal models of hyperactivity and attention disorders might underlie the observed phenotypes of the CLF line of rats.

Methylphenidate for attention-deficit/hyperactivity disorder in adults: a narrative review

RATIONALE

Psychostimulants, including methylphenidate (MPH), are the mainstay of pharmacotherapy for attention-deficit/hyperactivity disorder (ADHD) in adults. Even though MPH is the most commonly used medication for ADHD these days, there are relatively few resources available that provide comprehensive insight into the pharmacological and clinical features of the compound.

OBJECTIVE

The aim of this paper is to provide an up-to-date outline of the pharmacology and clinical utility of MPH for ADHD in adult patients.

METHODS

While conducting the narrative review, we applied structured search strategies covering the two major online databases (MEDLINE and Cochrane Central Register of Controlled Trials). In addition, we performed handsearching of reference lists of relevant papers.

RESULTS

Methylphenidate exhibits multimodal mechanism of action, working primarily as a dopamine and noradrenaline reuptake inhibitor. It also protects the dopaminergic system against the ongoing 'wearing off' (by securing a substantial reserve pool of the neurotransmitter, stored in the presynaptic vesicles). In placebo-controlled trials, MPH was shown to be moderately effective both against the core ADHD symptoms (standardized mean difference [SMD], 0.49; 95% confidence interval [CI], 0.35-0.64), and the accompanying emotion regulation deficits (SMD, 0.34; 95% CI, 0.23-0.45). The most common adverse events related to long-term treatment with MPH are decreased appetite (~ 20%), dry mouth (15%), heart palpitations (13%), gastrointestinal infections (~ 10%), and agitation/feeling restless (~ 10%).

CONCLUSIONS

There is substantial body of evidence to suggest that MPH is an effective and safe treatment option for adults with ADHD.