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Background: Everolimus is an oral mammalian target of rapamycin (mTOR) inhibitor used as an immunosuppressant and anticancer. Its pharmacokinetics is highly variable, it has a narrow therapeutic window and shows chronotoxicity with the best time at ZT13 and worst time at ZT1 (ZT; Zeitgeber time, time after light onset) in the preclinical setting. Objectives: In the present study, we aimed to investigate whether the pharmacokinetics of everolimus vary according to dosing time and whether sex and feeding status interfere with the chronopharmacokinetics. Method: A single dosage of 5 mg/kg everolimus was administered orally to C57BL/6J male and female mice, in fed or fasted states at ZT1‐rest and ZT13‐activity times and blood and tissue samples were collected at 0.5, 1, 2, 4, 12, and 24 h following drug administration. Ileum, liver, plasma, and thymus concentrations of everolimus were determined. Results: Females had a greater ileum AUC0–24h than males when fed (P = 0.043). Everolimus AUC0–24h in the liver was substantially greater at ZT1 than at ZT13 in a fasted state (P = 0.001). Plasma Cmax, AUC0–24h, and AUCtotal were not statistically significant between the groups (P = 0.098). In one of the target organs of everolimus, the thymus, males had considerably higher amounts at ZT1 than females (P = 0.029). Conclusion: Our findings imply that the pharmacokinetics of everolimus in mice may differ according to dosing time, sex, and feeding. Greater tissue distribution of everolimus at ZT1 may be associated with the worst tolerated time of everolimus. Our research suggests that oral chronomodulated everolimus therapy may be more effective and safer for cancer patients. [ABSTRACT FROM AUTHOR]

Chronopharmacology is a multidisciplinary field that investigates the impact of biological rhythms on drug effects and responses. It aims to optimize drug therapy by considering the timing and rhythm characteristics of biological events. Chronopharmacology focuses on designing drug dosing schedules that align with the body's natural biological rhythms, enhancing drug efficacy and safety while reducing adverse reactions. This approach holds significant promise in pharmacology and drug therapy, as it can revolutionize medication administration and patient care. Chronotherapeutics involves timing interventions such as surgery, physical agents, and psychotherapy to minimize toxicity and enhance treatment efficacy. It benefits translational medicine by considering underlying circadian rhythms in drug pharmacology, including pharmacokinetics and pharmacodynamics, as well as patients' physiology and disease pathology. Recent research focuses on targeting treatments toward rhythm-generating biologic timing systems to improve outcomes. Chronopharmacology has shown potential advantages in treating disorders such as peptic ulcer disease, cancer, allergic rhinitis, and rheumatoid arthritis. Challenges for chronopharmacology include lack of translation research, variability in therapeutic responses, replication of findings, optimized drug dosing schedules, clinical implementation, clock disruption, and standardization of chronopharmacological guidelines. In terms of pharmacology and medication therapy, chronopharmacology has a lot of promise. This strategy has the potential to change medicine administration and enhance patient care by utilizing biological rhythms and optimizing drug dose schedules. To fully realize the promise of chronopharmacology in clinical practice, additional study and validation of findings are required. [ABSTRACT FROM AUTHOR]

Mammalians' circadian pacemaker resides in the paired suprachiasmatic nuclei (SCN). SCN control biological rhythms such as the sleep-wake rhythm and homeostatic functions of steroid hormones and their receptors. Alterations in these biological rhythms are implicated in the outcomes of pathogenic conditions such as depression, diabetes, and cancer. Chronotherapy is about optimizing treatment to combat risks and intensity of the disease symptoms that vary depending on the time of day. Thus, conditions/diseases such as allergic rhinitis, arthritis, asthma, myocardial infarction, congestive heart failure, stroke, and peptic ulcer disease, prone to manifest severe symptoms depending on the time of day, would be benefited from chronotherapy. Monitoring rhythm, overcoming rhythm disruption, and manipulating the rhythms from the viewpoints of underlying molecular clocks are essential to enhanced chronopharmacotherapy. New drugs focused on molecular clocks are being developed to improve therapeutics. In this review, we provide a critical summary of literature reports concerning (a) the rationale/mechanisms for time-dependent dosing differences in therapeutic outcomes and safety of antitumor drugs, (b) the molecular pathways underlying biological rhythms, and (c) the possibility of pharmacotherapy based on the intra- and inter-individual variabilities from the viewpoints of the clock genes. [Display omitted] [ABSTRACT FROM AUTHOR]

Clock genes, circadian pacemaker resides in the paired suprachiasmatic nuclei (SCN), control various circadian rhythms in many biological processes such as physiology and behavior. Clock gene regulates many diseases such as cancer, immunological dysfunction, metabolic syndrome and sleep disorders etc. Chronotherapy is especially relevant, when the risk and/or intensity of the symptoms of disease vary predicably over time as exemplified by allergic rhinitis, arthritis, asthma, myocardial infarction, congestive heart failure, stroke, and peptic ulcer disease. Dosing time influences the effectiveness and toxicity of many drugs. The pharmacodynamics of medications as well as pharmacokinetics influences chronopharmacological phenomena. To escape from host immunity in the tumor microenvironment, cancer cells have acquired several pathways. Immune checkpoint therapy targeting programmed death 1 (PD-1) and its ligand (PD-L1) interaction had been approved for the treatment of patients with several types of cancers. Circadian expression of PD-1 is identified on tumor associated macrophages (TAMs), which is rationale for selecting the most appropriate time of day for administration of PD-1/PD-L1 inhibitors. The therapies for chronic kidney disease (CKD) are urgently needed because of a global health problem. The mechanism of the cardiac complications in mice with CKD had been related the GRP68 in circulating monocytes and serum accumulation of retinol. Development of a strategy to suppress retinol accumulation will be useful to prevent the cardiac complications of CKD. Therefore, we introduce an overview of the dosing time-dependent changes in therapeutic outcome and safety of drug for immune-related diseases.

The circadian timing system controls absorption, distribution, metabolism, and elimination processes of drug pharmacokinetics over a 24-h period. Exposure of target tissues to the active form of the drug and cytotoxicity display variations depending on the chronopharmacokinetics. For anticancer drugs with narrow therapeutic ranges and dose-limiting side effects, it is particularly important to know the temporal changes in pharmacokinetics. A previous study indicated that pharmacokinetic profile of capecitabine was different depending on dosing time in rat. However, it is not known how such difference is attributed with respect to diurnal rhythm. Therefore, in this study, we evaluated capecitabine-metabolizing enzymes in a diurnal rhythm-dependent manner. To this end, C57BL/6J male mice were orally treated with 500 mg/kg capecitabine at ZT1, ZT7, ZT13, or ZT19. We then determined pharmacokinetics of capecitabine and its metabolites, 5′-deoxy-5-fluorocytidine (5′DFCR), 5′-deoxy-5-fluorouridine (5′DFUR), 5-fluorouracil (5-FU), in plasma and liver. Results revealed that plasma C max and AUC0-6h (area under the plasma concentration-time curve from 0 to 6 h) values of capecitabine, 5′DFUR, and 5-FU were higher during the rest phase (ZT1 and ZT7) than the activity phase (ZT13 and ZT19) (p < 0.05). Similarly, C max and AUC0-6h values of 5′DFUR and 5-FU in liver were higher during the rest phase than activity phase (p < 0.05), while there was no significant difference in liver concentrations of capecitabine and 5′DFCR. We determined the level of the enzymes responsible for the conversion of capecitabine and its metabolites at each ZT. Results indicated the levels of carboxylesterase 1 and 2, cytidine deaminase, uridine phosphorylase 2, and dihydropyrimidine dehydrogenase (p < 0.05) are being rhythmically regulated and, in turn, attributed different pharmacokinetics profiles of capecitabine and its metabolism. This study highlights the importance of capecitabine administration time to increase the efficacy with minimum adverse effects. [ABSTRACT FROM AUTHOR]

Clock genes, circadian pacemaker resides in the paired suprachiasmatic nuclei (SCN), control various circadian rhythms in many biological processes such as physiology and behavior. Clock gene regulates many diseases such as cancer, immunological dysfunction, metabolic syndrome and sleep disorders etc. Chronotherapy is especially relevant, when the risk and/or intensity of the symptoms of disease vary predicably over time as exemplified by allergic rhinitis, arthritis, asthma, myocardial infarction, congestive heart failure, stroke, and peptic ulcer disease. Dosing time influences the effectiveness and toxicity of many drugs. The pharmacodynamics of medications as well as pharmacokinetics influences chronopharmacological phenomena. To escape from host immunity in the tumor microenvironment, cancer cells have acquired several pathways. Immune checkpoint therapy targeting programmed death 1 (PD-1) and its ligand (PD-L1) interaction had been approved for the treatment of patients with several types of cancers. Circadian expression of PD-1 is identified on tumor associated macrophages (TAMs), which is rationale for selecting the most appropriate time of day for administration of PD-1/PD-L1 inhibitors. The therapies for chronic kidney disease (CKD) are urgently needed because of a global health problem. The mechanism of the cardiac complications in mice with CKD had been related the GRP68 in circulating monocytes and serum accumulation of retinol. Development of a strategy to suppress retinol accumulation will be useful to prevent the cardiac complications of CKD. Therefore, we introduce an overview of the dosing time-dependent changes in therapeutic outcome and safety of drug for immune-related diseases. [ABSTRACT FROM AUTHOR]

Introduction: The 24-hour variations in drug absorption, distribution, metabolism, and elimination, collectively known as pharmacokinetics, are fundamentally influenced by rhythmic physiological processes regulated by the molecular clock. Recent advances have elucidated the intricacies of the circadian timing system and the molecular interplay between biological clocks, enzymes and transporters in preclinical level., Area Covered: Circadian rhythm of the drug metabolizing enzymes and carrier efflux functions possess a major role for drug metabolism and detoxification. The efflux and metabolism function of intestines and liver seems important. The investigations revealed that the ABC and SLC transporter families, along with cytochrome p -450 systems in the intestine, liver, and kidney, play a dominant role in the circadian detoxification of drugs. Additionally, the circadian control of efflux by the blood-brain barrier is also discussed., Expert Opinion: The influence of the circadian timing system on drug pharmacokinetics significantly impacts the efficacy, adverse effects, and toxicity profiles of various drugs. Moreover, the emergence of sex-related circadian changes in the metabolism and detoxification processes has underscored the importance of considering gender-specific differences in drug tolerability and pharmacology. A better understanding of coupling between central clock and circadian metabolism/transport contributes to the development of more rational drug utilization and the implementation of chronotherapy applications.

Circadian fluctuations in the plasma concentration of 5-fluorouracil impede the accurate estimation of target therapeutic concentrations in the long-term infusion or oral 5-fluorouracil-based prodrug regimen. We evaluated the circadian patterns of plasma 5-fluorouracil concentrations in rats using population pharmacokinetic model. Rats were divided into 2 groups, and a continuous infusion (50 mg/m2/h) for 48 h was initiated with or without a bolus injection of 60 mg/kg 5-fluorouracil. In the group not administered a loading dose, significant circadian variation of plasma 5-fluorouracil concentration was observed. In contrast, in the loading dose group, this circadian variation disappeared. Additionally, decreased hepatic dihydropyrimidine dehydrogenase activity was observed. Population model analysis revealed that the concentrations of 5-fluorouracil followed a 24-h cosine circadian curve, representing an overall 1.8-fold increase from a nadir to a peak, with a relative amplitude (% of mesor) of 28%. The circadian 5-fluorouracil clearance pattern in the infusion-regimen was consistent with previously reported pattern for capecitabine and uracil-tegafur. In the recently modified regimen omitting the bolus injection of 5-fluorouracil, the circadian variations should be considered for blood sampling time points in therapeutic drug monitoring. The chronomodulated chemotherapy using oral prodrug administration could be established based on accumulating evidence in the infusion-regimen. [ABSTRACT FROM AUTHOR]

Metabolism and transport of many drugs oscillate with times of the day (solar time), resulting in circadian time-dependent drug exposure and pharmacokinetics. Time-dependent pharmacokinetics (also known as chronopharmacokinetics) is associated with time-varying drug effects and toxicity. This review summarizes drug-metabolizing enzymes and transporters with rhythmic expressions in the liver, intestine and/or kidney. Correlations of these diurnal proteins with circadian variations in drug exposure and effects/toxicity are covered. We also discuss the molecular mechanisms for circadian control of enzymes and transporters. Mechanism-based chronopharmacokinetics would facilitate a better understanding of chronopharmacology and the design of time-specific drug delivery systems, ultimately leading to improved drug efficacy and minimized toxicity. [ABSTRACT FROM AUTHOR]

Scientific evidence that circadian rhythms affect pharmacokinetics and pharmacodynamics has highlighted the importance of drug dosing-time. Circadian oscillations alter drug absorption, distribution, metabolism, and excretion (ADME) as well as intracellular signaling systems, target molecules (e.g., receptors, transporters, and enzymes), and gene transcription. Although several antidepressant drugs are clinically available, less than 50% of depressed patients respond to first-line pharmacological treatments. Chronotherapeutic approaches to enhance the effectiveness of antidepressants are not completely known. Even so, experimental results found until this day suggest a positive influence of drug dosing-time on the efficacy of depression therapy. On the other hand, antidepressants have also demonstrated to modulate circadian rhythmicity and sleep–wake cycles. This review aims to evidence the potential of chronotherapy to improve the efficacy and/or safety of antidepressants. It includes pre-clinical and clinical studies that demonstrate the relevance of determining the most appropriate time of administration for antidepressant drugs. In parallel, their positive influence on the resynchronization of disrupted circadian rhythms is also herein discussed. It is expected that this review will promote the investigation of chronotherapy for the treatment of depression, contribute to a better understanding of the relationship between antidepressants and circadian rhythms, and consequently promote the development of new therapeutics.

The objective of the optimization of pharmacotherapy compliant with the basic rules of clinical pharmacology is its maximum individualization, ensuring paramount effectiveness and security of the patient’s therapy. Thus, multiple factors that are decisive in terms of uniqueness of treatment of the given patient must be taken into consideration, including, but not limited to, the patient’s age, sex, concomitant diseases, special physiological conditions (e.g., pregnancy, lactation, extreme age groups), polypharmacotherapy and polypragmasia (particularly related to increased risk of drug interactions), and patient’s phenotypic response to the administered drug with possible genotyping. Conducting therapy while monitoring the concentration of certain drugs in blood (Therapeutic Drug Monitoring; TDM procedure) is also one of the factors enabling treatment individualization. Furthermore, another material, and yet still a marginalized pharmacotherapeutic factor, is chronopharmacology, which indirectly determines the values of drug concentrations evaluated in the TDM procedure. This paper is a brief overview of chronopharmacology, especially chronopharmacokinetics, and its connection with the clinical interpretation of the meaning of the drug concentrations determined in the TDM procedure.

In clinical practice, circadian rhythms play a prominent role in pharmacokinetics and cell responses to therapy, hence necessitating in designing a defined protocol for drug administration. Clinical evidence for chronopharmacological behavior of cardiovascular active drugs in human subjects has been limited for amlodipine. Hence, the present study was undertaken to study the chronopharmacokinetic and chronopharmacodynamic phenomena of amlodipine and evaluate the effect of time of dosage in hypertensive subjects. Single oral dose of amlodipine was administered to the hypertensive/normotensive subjects either morning or evening to assess the pharmacokinetic profile after morning dosing or evening dosing, respectively. PK parameters obtained revealed that Tmax was shorter and Cmax was greater after evening dosing than the morning dosing in both hypertensive and normotensive subjects. These observations were comparable with the hypothesis that amlodipine is absorbed rapidly when it is given during the night time. Also, the changes in systolicBP, DiastolicBP, and heart rate in comparison to the respective circadian baseline values were markedly different depending on the time and dosing. SBP and HR were significantly reduced after evening dosing with slight difference in measurement of DBP in hypertensive patients. Hence, it can be concluded that prescription of antihypertensive medications containing amlodipine, to be administered at night offers highly efficacious means to control BP without the need to increase either the dose or number of medications. The current treatment strategy method involves delivery of medications, so that they are synchronized in time to biological need that varies according to the chronobiology of the targeted tissues.

Glucocorticoids influence a wide array of metabolic, anti-inflammatory, immunosuppressive, and cognitive signaling processes, playing an important role in homeostasis and preservation of normal organ function. Synthesis is regulated by the hypothalamic-pituitary-adrenal (HPA) axis of which cortisol is the primary glucocorticoid in humans. Synthetic glucocorticoids are important pharmacological agents that augment the anti-inflammatory and immunosuppressive properties of endogenous cortisol and are widely used for the treatment of asthma, Crohn's disease, and rheumatoid arthritis, amongst other chronic conditions. The homeostatic activity of cortisol is disrupted by the administration of synthetic glucocorticoids and so there is interest in developing treatment options that minimize HPA axis disturbance while maintaining the pharmacological effects. Studies suggest that optimizing drug administration time can achieve this goal. The present review provides an overview of endogenous glucocorticoid activity and recent advances in treatment options that have further improved patient safety and efficacy with an emphasis on chronopharmacology. Unlabelled Image [ABSTRACT FROM AUTHOR]

[Display omitted] CYP2A5, an enzyme responsible for metabolism of diverse drugs, displays circadian rhythms in its expression and activity. However, the underlying mechanisms are not fully established. Here we aimed to investigate a potential role of CRY1/2 (circadian clock modulators) in circadian regulation of hepatic CYP2A5. Regulatory effects of CRY1/2 on CYP2A5 were determined using Cry1 -null and Cry2 -null mice, and validated using AML-12, Hepa1-6 and HepG2 cells. CYP2A5 activities both in vivo and in vitro were assessed using coumarin 7-hydroxylation as a probe reaction. mRNA and protein levels were detected by qPCR and western blotting, respectively. Regulatory mechanism was studied using a combination of luciferase reporter assays, chromatin immunoprecipitation (ChIP) and co-immunoprecipitation (Co-IP). We found that ablation of Cry1 or Cry2 in mice reduced hepatic CYP2A5 expression (at both mRNA and protein levels) and blunted its diurnal rhythms. Consistently, these knockouts showed decreased CYP2A5 activity (characterised by coumarin 7-hydroxylation) and a loss of its time-dependency, as well as exacerbated coumarin-induced hepatotoxicity. Cell-based assays confirmed that CRY1/2 positively regulated CYP2A5 expression and rhythms. Based on combined luciferase reporter, ChIP and Co-IP assays, we unraveled that CRY1/2 interacted with E4BP4 protein to repress its inhibitory effect on Cyp2a5 transcription and expression. In conclusion, CRY1/2 regulate rhythmic CYP2A5 in mouse liver through repression of E4BP4. These findings advance our understanding of circadian regulation of drug metabolism and pharmacokinetics. [ABSTRACT FROM AUTHOR]

Abstract Uracil-tegafur (UFT) is an oral anticancer drug containing uracil and 5‑fluorouracil prodrug tegafur and is widely used for adjuvant chemotherapy of colorectal cancer. Although clinical data show circadian variations in plasma 5‑fluorouracil concentrations during its long-term infusion, and feasibility studies of chronomodulated administration have been previously reported, the circadian pattern in plasma 5‑fluorouracil concentration after UFT administrations remains unclear. The aim of this study was to identify factors causing circadian variations in UFT pharmacokinetics and estimate circadian patterns of plasma 5‑fluorouracil concentration corresponding to UFT dosing time in rats. Rats were orally administered UFT (15 mg/kg as tegafur) at three different times of the day: 07:00 (23 h after light onset, HALO), 13:00 (5 HALO), or 19:00 (11 HALO), and then plasma concentrations of tegafur, 5‑fluorouracil, and uracil were measured after UFT administration. We found that the area under the plasma concentration-time curves ( AUC 0−∞ ) of 5‑fluorouracil depended on the UFT dosing time of day with a 2.4-fold difference between the peak (at 19:00: 13.7 ± 1.4 μmol·h/L) and trough (at 13:00: 5.6 ± 1.3 μmol·h/L). The simulated population mean clearance of 5‑fluorouracil followed a 24-h cosine circadian curve, with the highest value in the early light phase being 2.2-fold higher than the lowest value in the early dark phase, which was an inverse circadian pattern compared to the plasma 5‑fluorouracil concentration. The plasma tegafur levels suggested that circadian variation in tegafur absorption and conversion to 5‑fluorouracil are factors causing variations in plasma 5‑fluorouracil levels following UFT administration. In conclusion, the circadian pattern of 5‑fluorouracil clearance and circadian variations in tegafur pharmacokinetics are important determinants of plasma 5‑fluorouracil concentrations following UFT administration. This knowledge could help in developing a chronomodulated administration strategy of UFT for improving clinical outcomes. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Capecitabine, an orally available prodrug of 5-fluorouracil, is widely used to treat patients with colorectal cancer. Although various studies have shown circadian variations in plasma 5-fluorouracil concentrations during long-term infusion, it is still unknown whether circadian variations also exist following administration of capecitabine. The present study aimed to investigate whether the pharmacokinetics of capecitabine and its metabolites, including 5-fluorouracil, vary according to administration time in rats. Rats were orally administered capecitabine (180 mg/kg) at 07:00 (23 h after light onset, HALO), 13:00 (5 HALO), or 19:00 h (11 HALO). Plasma concentrations of capecitabine and its metabolites, such as 5′-deoxy-5-fluorocytidine (5′-DFCR), 5′-deoxy-5-fluorouridine (5′-DFUR), and 5-fluorouracil, were determined after capecitabine administration. The results showed that the t 1/2 and AUC 0–∞ values of 5-fluorouracil differed as a function of the dosing time of capecitabine. The maximum and minimum mean t 1/2 values of 5-fluorouracil were obtained when the drug was administered at 07:00 h (23 HALO: 3.1 ± 1.2 h) and 13:00 h (5 HALO: 1.5 ± 0.6 h), respectively. The AUC 0–∞ value of 5-fluorouracil at 07:00 h (23 HALO: 533.9 ± 195.7 μmol ∙ h/L) was 1.8-fold higher than the value at 13:00 h (5 HALO: 302.5 ± 157.1 μmol ∙ h/L). The clearance of 5-fluorouracil followed a cosine circadian curve, and the simulated population mean clearance was highest at rest times and lowest during active times in rats. The results for the plasma 5′-DFCR and 5′-DFUR levels indicated that circadian variations in the sequential metabolism of capecitabine to 5-fluorouracil would also affect plasma 5-fluorouracil levels following capecitabine administration. In conclusion, the pharmacokinetics of capecitabine and its metabolites, including 5-fluorouracil, varied according to time of dosing, suggesting that the capecitabine administration time is an important factor in achieving sufficient efficacy and reducing toxicity in patients. [ABSTRACT FROM AUTHOR]

Chronotherapy is especially relevant, when the risk and/or intensity of the symptoms of disease vary predicably over time as exemplified by allergic rhinitis, arthritis, asthma, myocardial infarction, congestive heart failure, stroke, and peptic ulcer disease. The effectiveness and toxicity of many drugs vary depending on dosing time. Such chronopharmacological phenomena are influenced by not only the pharmacodynamics but also pharmacokinetics of medications. One approach to increasing the efficiency of pharmacotherapy is administering drugs at times during which they are best tolerated. From viewpoints of pharmaceutics, the application of biological rhythm to pharmacotherapy may be accomplished by the appropriate timing of conventionally formulated tabletes and capsules, and the special drug delivery system to synchronize drug concentrations to rhythms in disease activity. In all living organisms, one of the most indispensable biological functions is the circadian clock (suprachiasmatic nucleus; SCN), which acts like a multifunction timer to regulate homeostatic systems such as sleep and activity, hormone levels, appetite, and other bodily functions with 24 hr cycles. Clock genes were identified as the genes that ultimately control a vast array of circadian rhythms in physiology and behavior. Clock gene regulates several disease such as cancer, metabolic syndrome and sleep etc. Therefore, we introduce an overview of the dosing time-dependent alterations in therapeutic outcome and safety of drug. The underlying mechanisms and usefulness are introduced from viewpoints of clock genes and the possibility of pharmacotherapy based on clock genes. [ABSTRACT FROM AUTHOR]

The circadian timing system (CTS) controls various biological functions in mammals including xenobiotic metabolism and detoxification, immune functions, cell cycle events, apoptosis and angiogenesis. Although the importance of the CTS is well known in the pharmacology of drugs, it is less appreciated at the clinical level. Genome-wide studies highlighted that the majority of drug target genes are controlled by CTS. This suggests that chronotherapeutic approaches should be taken formany drugs to enhance their effectiveness. Currently chronotherapeutic approaches are successfully applied in the treatment of different types of cancers. The chronotherapy approach has improved the tolerability and antitumor efficacy of anticancer drugs both in experimental animals and in cancer patients. Thus, chronobiological studies have been of importance in determining the most appropriate time of administration of anticancer agents to minimize their side effects or toxicity and enhance treatment efficacy, so as to optimize the therapeutic ratio. This review focuses on the underlying mechanisms of the circadian pharmacology i.e., chronopharmacokinetics and chronopharmacodynamics of anticancer agents with the molecular aspects, and provides an overview of chronotherapy in cancer and some of the recent advances in the development of chronopharmaceutics. [ABSTRACT FROM AUTHOR]

In clinical practice, circadian rhythms play a prominent role in pharmacokinetics and cell responses to therapy, hence necessitating in designing a defined protocol for drug administration. Clinical evidence for chronopharmacological behavior of cardiovascular active drugs in human subjects has been limited for amlodipine. Hence, the present study was undertaken to study the chronopharmacokinetic and chronopharmacodynamic phenomena of amlodipine and evaluate the effect of time of dosage in hypertensive subjects. Single oral dose of amlodipine was administered to the hypertensive/normotensive subjects either morning or evening to assess the pharmacokinetic profile after morning dosing or evening dosing, respectively. PK parameters obtained revealed thatTmaxwas shorter andCmaxwas greater after evening dosing than the morning dosing in both hypertensive and normotensive subjects. These observations were comparable with the hypothesis that amlodipine is absorbed rapidly when it is given during the night time. Also, the changes in systolicBP, DiastolicBP, and heart rate in comparison to the respective circadian baseline values were markedly different depending on the time and dosing. SBP and HR were significantly reduced after evening dosing with slight difference in measurement of DBP in hypertensive patients. Hence, it can be concluded that prescription of antihypertensive medications containing amlodipine, to be administered at night offers highly efficacious means to control BP without the need to increase either the dose or number of medications. The current treatment strategy method involves delivery of medications, so that they are synchronized in time to biological need that varies according to the chronobiology of the targeted tissues. [ABSTRACT FROM PUBLISHER]

Bile acid homeostasis is maintained by liver synthesis, bile duct secretion, microbial metabolism and intestinal reabsorption into the blood. When drug insults result in liver damage, the variances of bile acids (BAs) are related to the physiological status of the liver. Here, we established a method to simultaneously quantify 19 BAs in rat plasma, liver, bile and different intestinal section contents (duodenum, jejunum, ileum, cecum and colon) using high-performance liquid chromatography-tandem mass spectrometry (LC–MS/MS) to reveal the pattern of bile acid homeostasis in the enterohepatic circulation of bile acids in physiological situations. Dynamic changes in bile acid composition appeared throughout the enterohepatic circulation of the BAs; taurine- and glycine-conjugated BAs and free BAs had different dynamic homeostasis levels in the circulatory system. cholic acid (CA), beta-muricholic acid (beta-MCA), lithocholic acid (LCA), glycocholic acid (GCA) and taurocholic acid (TCA) greatly fluctuated in the bile acid pool under physiological conditions. Taurine- and glycine-conjugated bile acids constituted more than 90% in the bile and liver, whereas GCA and TCA accounted for more than half of the total bile acids and the secretion of bile mainly via conjugating with taurine. While over 80% of BAs in plasma were unconjugated bile acids, CA and HDCA were the most abundant elements. Unconjugated bile acids constituted more than 90% in the intestine, and CA, beta-MCA and HDCA were the top three bile acids in the duodenum, jejunum and ileum content, but LCA and HDCA were highest in the cecum and colon content. As the main secondary bile acid converted by microflora in the intestine, LCA was enriched in the cecum and DCA mostly in the colon. As endogenous substances, the concentrations of plasma BAs were closely related to time rhythm and diet. In conclusion, analyzing detailed BA profiles in the enterohepatic circulation of bile acids in a single run is possible using LC–MS/MS. Based on the physiological characteristics of the metabolic profiling of 19 BAs in the total bile acid pool and the time rhythm variation of the endogenous bile acids, this study provided a new valuable method and theoretical basis for the clinical research of bile acid homeostasis. [ABSTRACT FROM AUTHOR]

Aim: This study investigated the impact of food intake and circadian rhythms on the pharmacokinetics of mavacamten. Materials & methods: A sensitive bioanalytical method for quantifying mavacamten in rat plasma was developed and validated. This method was applied to assess the effect of chronopharmacology and food intake on the pharmacokinetics of mavacamten in rats. Results: A circadian variation at two doses resulted in significant changes in the volume of distribution, clearance and time of maximum plasma concentration of mavacamten (p < 0.05). In addition, food intake had an insignificant impact on the pharmacokinetic parameters except for the time of maximum plasma concentration (p < 0.05). Conclusion: These pharmacokinetic changes and human chronotype findings will help optimize dosing time.

Aim. To compare the pharmacokinetics and pharmacodynamics of verapamil retard, regularly taken by patients with Stage I-II arterial hypertension (AH). Material and methods. The effects of the administration time (morning vs. evening) on verapamil retard pharmacokinetics were investigated. This open, randomised, cross-over study included 14 patients with Stage I-II AH, who were regularly administered verapamil retard for 3 weeks. Before the active therapy started, all antihypertensive medications were withdrawn, with an exception of short-acting agents (“wash-out” period). Two weeks later, the patients were administered verapamil retard, according to the randomisation scheme, and were recommended to take one tablet in the morning or evening, at the same time every day. The first administration was at the clinic, under medical supervision. Three weeks later, the participants were hospitalised for pharmacokinetics assessment. Seven days after the end of the first treatment course, a second course started, with an inverted time of verapamil retard administration. Blood concentration of non-modified verapamil was measured by high-performance liquid chromatography with fluorescent detection.Results. Significant differences in pharmacokinetics were observed for morning vs. evening verapamil administration. The respective maximal verapamil concentrations were 239,7±152,3 vs. 148,6±107,4 ng/ml (p

[Display omitted] We aimed to investigate the potential role of NPAS2 in controlling diurnal expression and activity of hepatic CYP1A2 and to determine the underlying mechanisms. Regulatory effects of NPAS2 on CYP1A2 were determined using Npas2 knockout (Npas2 -/-) mice as well as AML-12, Hepa1-6 and HepG2 cells. mRNA and protein levels were detected by reverse transcription-quantitative real-time PCR and western blotting, respectively. In vitro and in vivo CYP1A2 activities were respectively evaluated using the probe substrates phenacetin and theophylline. Transcriptional regulation was investigated using luciferase reporter assays and ChIP-Seq analysis. Loss of Npas2 in mice decreased CYP1A2 expression (at both mRNA and protein levels) and blunted its rhythmicity in the liver. Likewise, Npas2 ablation down-regulated the enzymatic activity of CYP1A2 (probed by metabolism of phenacetin and theophylline) and abrogated its time-dependency. Cell-based assays confirmed that NPAS2 positively regulated CYP1A2 expression. Mechanistic study indicated that NPAS2 trans -activated Cyp1a2 through its specific binding to the −416 bp E-box-like element within the gene promoter. In conclusion, NPAS2 was identified as a key transcriptional regulator of diurnal expression of hepatic CYP1A2 in mice. Our findings have implications for improved understanding of circadian metabolism and chronopharmacokinetics. [ABSTRACT FROM AUTHOR]

Aim The objective of this study was to investigate whether the pharmacokinetics of orally administered levofloxacin show 24 h variation. Levofloxacin was used as a model compound for solubility and permeability independent absorption and passive renal elimination. Methods In this single centre, crossover, open label study, 12 healthy subjects received an oral dose of 1000 mg levofloxacin at six different time points equally divided over the 24 h period. Population pharmacokinetic modelling was used to identify potential 24 h variation in the pharmacokinetic parameters of this drug. Results The pharmacokinetics of levofloxacin could be described by a one compartment model with first order clearance and a transit compartment to describe drug absorption. The fit of the model was significantly improved when the absorption rate constant was described as a cosine function with a fixed period of 24 h, a relative amplitude of 47% and a peak around 08.00 h in the morning. Despite this variation in absorption rate constant, simulations of a once daily dosing regimen showed that tmax, Cmax and the area under the curve at steady-state were not affected by the time of drug administration. Conclusion The finding that the absorption rate constant showed considerable 24 h variation may be relevant for drugs with similar physicochemical properties as levofloxacin that have a narrower therapeutic index. Levofloxacin, however, can be dosed without taking into account the time of day, at least in terms of its pharmacokinetics. [ABSTRACT FROM AUTHOR]

[Display omitted] Dependence of pharmacokinetics and drug effects (efficacy and toxicity) on dosing time has long been recognized. However, significant progress has only recently been made in our understanding of circadian rhythms and their regulation on drug pharmacokinetics, efficacy and toxicity. This review will cover the relevant literature and a series of publications from our work summarizing the effects of circadian rhythms on drug pharmacokinetics, and propose that the influence of circadian rhythms on pharmacokinetics are ultimately translated into therapeutic effects and side effects of drugs. Evidence suggests that daily rhythmicity in expression of drug-metabolizing enzymes and transporters necessary for drug ADME (absorption, distribution, metabolism and excretion) are key factors determining circadian pharmacokinetics. Newly discovered mechanisms for circadian control of the enzymes and transporters are covered. We also discuss how the rhythms of drug-processing proteins are translated into circadian pharmacokinetics and drug chronoefficacy/chronotoxicity, which has direct implications for chronotherapy. More importantly, we will present perspectives on the challenges that are still needed for a breakthrough in translational research. In addition, knowledge of the circadian influence on drug disposition has provided new possibilities for novel pharmacological strategies. Careful application of pharmacokinetics-based chronotherapy strategies can improve efficacy and reduce toxicity. Circadian rhythm-mediated metabolic and transport strategies can also be implemented to design drugs. [ABSTRACT FROM AUTHOR]

The expression "as sure as night follows a day" emulates those certain cycles in the environment that are always stable. Circadian rhythms are a group of processes that occur within the body in synchronisation with the external factors in a 24 h cycle. Changes in lifestyle and work shifts have disrupted these stable rhythms, which is a leading cause of lifestyle diseases. Associations between these biological clocks and diseases are abundant. However, it is also known that certain drugs work more efficiently and have minimum toxicity when given during a particular phase of the circadian cycle. Chronotherapeutics focuses on treating diseases according to the endogenous processes which mediate xenobiotic metabolism and drug response at a cellular level. Therefore, treatment of those diseases that show aggravation of symptoms according to the circadian rhythms at a particular time is highly beneficial by chronotherapy. In this article, we have emphasised how the changes in rhythms caused diseases and how chronotherapeutic approaches such as controlled drug release technologies can be a better option for these circadian manipulations that seem to influence all types of disease conditions., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

The basic pharmacokinetic parameters of MTX administered as monotherapy as well as in the combined therapy with simultaneous and prior administation of FU were investigated. The parameters were determined in the two-compartment open system on the basis of measurement of MTX levels in mice after i.p. administration of a single dose 20 mg/ kg of the drug. The FU dose was 20 mg/kg, too. The effect of the circadian rhythm on the kinetics of MTX have been taken into consideration. In one series of experiments the drugs were administered in the morning and in the other during midday hours . The statistical analysis of the obtained results showed the essential effect of the administration time on the pharmacokinetic parameters of MTX in mice. The statistical significal differences could be found: C max, AUC, CL, T0,5 . The differences in T0,5 , parameter resulting from coadministration of FU with the same circadian rhythm of MTX administration have been observed.

Diurnal changes in the activity of drug metabolizing enzymes may contribute to the variability in drug disposition and drug effects. The aim of this study was to quantify the circadian rhythmicity exhibited by hepatic CYP3A. A 10 μg/kg intravenous bolus dose, followed by a 30-hour 4 μg/kg/h intravenous infusion of midazolam, used as a probe substrate for hepatic CYP3A activity, was administered to 16 healthy volunteers (8 males and 8 females). Blood samples were drawn hourly for 24 hours after achieving steady state, and plasma concentrations of midazolam and its main metabolite 1-OH midazolam were determined. Population pharmacokinetic analysis was performed using nonlinear mixed effects modeling. One-compartment pharmacokinetic models best described midazolam and 1-OH midazolam pharmacokinetic disposition. An unequivocal but minor diurnal pattern was identified in the midazolam plasma concentration profiles, which was described using a cosine function with a 24-hours period. The fluctuation in the relative CYP3A activity ranged between 10% above average around 15:00, and 10% below average around 03:00. None of the covariates tested had a significant impact on the parameters estimated. Although a diurnal pattern in hepatic CYP3A activity was identified, its magnitude suggests that it is small and without clinical significance for drug therapy. [ABSTRACT FROM AUTHOR]

Many weakly basic amine-containing drugs are known to be extensively sequestered in acidic lysosomes by an ion trapping-type mechanism. The entrapment of drugs in lysosomes has been shown to influence drug activity, cancer cell selectivity, and pharmacokinetics and can cause the hyperaccumulation of various lipids associated with lysosomes. In this work, we have investigated the prolonged time-dependent effects of drugs on lysosomal properties. We have evaluated two amine-containing drugs with intermediate (propranolol) and high (halofantrine) relative degrees of lipophilicity. Interestingly, the cellular accumulation kinetics of these drugs exhibited a biphasic characteristic at therapeutically relevant exposure levels with an initial apparent steady-state occurring at 2 days followed by a second stage of enhanced accumulation. We provide evidence that this secondary drug accumulation coincides with the nuclear localization of transcription factor EB, a master regulator of lysosome biogenesis, and the appearance of an increased number of smaller and lipid-laden lysosomes. Collectively, these results show that hydrophobic lysosomotropic drugs can induce their own cellular accumulation in a time-dependent fashion and that this is associated with an expanded lysosomal volume. These results have important therapeutic implications and may help to explain sources of variability in drug pharmacokinetic distribution and elimination properties observed in vivo. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:3287-3296, 2014 [ABSTRACT FROM AUTHOR]

OBJECTIVES: At present it is known that the adjustment of the anticancer therapy to the circadian rhythms in tissues reduces the toxicity of the treatment. Chronotherapy also increases the efficacy of the anti-cancer treatment, which has been proved for many drugs. Sunitinib is a tyrosine kinase inhibitor, which is broadly used for the treatment of numerous cancers. The aim of the study was a comparison of the concentrations and pharmacokinetics of sunitinib after a single administration to rabbits at 08:00 (control group) and 20:00. Additionally, the effect of sunitinib on glucose levels was investigated. MATERIALS AND METHODS: The research was carried out on two groups of rabbits: I08:00, a group with the drug administered at 08:00 (n=8) and II20:00, a group with the drug administered at 20:00 (n=8). The rabbits were treated with sunitinib at an oral dose of 25 mg. Plasma concentrations of sunitinib and its metabolite (SU12662) were measured with a validated HPLC method with UV detection. RESULTS: The comparison of the sunitinib Cmax and AUC0-t in the group with sunitinib administered at 20:00 with the control group gave the ratios of 2.20 (90% confidence interval (CI) (2.17; 2.22) and 1.64 (1.61; 1.68), respectively. Statistically significant differences between the groups under analysis were revealed for Cmax (p < 0.0001), AUC0-t (p = 0.0079), AUC0-∞ (p = 0.0149), and tmax (p = 0.0085). The mean glycemia drop was higher in group I08:00. than in group II20:00 (22.7% vs. 14.3%; p = 0.0622). The glycemia values returned to the initial values in 24 h after the administration of the drug in both groups. CONCLUSIONS: The research proved a significant influence of the time-of-day administration on the pharmacokinetics of sunitinib. [ABSTRACT FROM AUTHOR]

The present work aims to investigate whether the pharmacokinetics of the active metabolite mycophenolic acid (MPA) varies according to the circadian dosing-time of mycophenolate mofetil (MMF). A total of 180 male Wistar rats aged 8 weeks and synchronized for 3weeks to 12h light and 12h dark were used. A single dose of 200mg/kg of MMF was administrated in rats by i.p route at either of the four different circadian stages (1, 7, 13, and 19 Hours After Light Onset, HALO) (45 rats/circadian time). At each circadian stage, blood samples were collected at 5, 10, 15, 20, 30min, 1h, 1h 30min, 2h, 3h, 4h, 6h, 8h, 12h and 24h following drug injection. Plasma MPA concentrations were analyzed for each sample using a validated high-performance liquid chromatography (RP-HPLC) method. T max of MPA remained similar whatever the circadian time of injection mean T max =30min). However, the peak of plasma concentration C max varied significantly according to the circadian dosing-time. Maximum and minimum C max were obtained when MMF was injected at 7 HALO (69.1μg/ml) and at 19 HALO (22.7±1.74μg/ml) respectively. AUC0 – 24 varied significantly according to the circadian-time of injection (166.33±10.54mgh/L at 7 HALO vs 80.27±2.33mgh/L at 19 HALO) (p <0.05). The highest and lowest mean values of plasma clearance (CL calculated as Dos/AUC) were observed at 19 HALO (2.45±0.07L/h/kg) and at 7 HALO (1.08±0.06L/h/kg) respectively (p <0.05). Cosinor showed a circadian rhythm in the pharmacokinetic parameters C max, AUC0 – 24 and plasma clearance. The mechanism of circadian rhythm in MMF tolerance might be partly explained by the circadian variation of pharmacokinetics since the time (7 HALO) of maximum hematological and digestive toxicity corresponds to that of the lowest plasma clearance on the highest C max and AUC0 – 24 of MMF. [ABSTRACT FROM AUTHOR]

In humans many physiological processes present diurnal variations controlled by an underlying circadian clock. Both anaesthesia and circadian clock may influence each other. Recent lines of evidence have also suggested that natural sleep and anaesthesia may be more similar than previously realized. Sleep deprivation enhances the potency of anaesthetics, such as propofol, establishing a link between the need for and anaesthesia. Works on rats suggest that during prolonged anaesthesia, sleep need does not accrue and that recovery from sleep deprivation can occur during anaesthesia. Some receptor-based effects of general anaesthetics appear to occur at the tuberomammillary nucleus (TMN) of the hypothalamus, a known sleep regulatory center in the brain. For many drugs used in anaesthesia the time-of-day effect has been confirmed, however mostly on animals. Further studies on humans are required to verify the obtained results. Despite of typical considerations for drug dosing, such as age, gender, weight, the diurnal fluctuations in drug responses may be important. Considering the time-of-day as a covariate for PK/PD (Pharmacokinetics/Pharmacodynamics) modeling of anaesthetic drugs in volunteers as well as in clinical settings the real role of circadian rhythms in various clinical conditions should be proven. Our aim was to review recent advances in our understanding of the relevance of circadian rhythms for anaesthesia as well as the methodological problems and considerations for assessing circadian rhythms in laboratory conditions and clinical settings. [ABSTRACT FROM AUTHOR]