Chronopharmacokinetics of valproic acid following constant-rate administration in mice

Chronopharmacology of immune-related diseases

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.

Daytime Restricted Feeding Modifies the Temporal Expression of CYP1A1 and Attenuated Damage Induced by Benzo[a]pyrene in Rat Liver When Administered before CYP1A1 Acrophase

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that heterodimerizes with the AhR nuclear translocator (ARNT) to modulate CYP1A1 expression, a gene involved in the biotransformation of benzo[a]pyrene (BaP). The AhR pathway shows daily variations under the control of the circadian timing system. Daytime restricted feeding (DRF) entrains the expression of genes involved in the processing of nutrients and xenobiotics to food availability. Therefore, we evaluate if temporal AhR, ARNT, and CYP1A1 hepatic expression in rats are due to light/dark cycles or fasting/feeding cycles promoted by DRF. Our results show that AhR oscillates throughout the 24 h period in DRF and ad libitum feeding rats (ALF), showing maximum expression at the same time points. DRF modified the peak of ARNT expression at ZT5; meanwhile, ALF animals showed a peak of maximum expression at ZT17. An increased expression of CYP1A1 was linked to the meal time in both groups of animals. Although a high CYP1A1 expression has been previously associated with BaP genotoxicity, our results show that, compared with the ALF group, DRF attenuated the BaP-CYP1A1 induction potency, the liver DNA-BaP adducts, the liver concentration of unmetabolized BaP, and the blood aspartate aminotransferase and alanine aminotransferase activities when BaP is administered prior to the acrophase of CYP1A1 expression. These results demonstrate that DRF modifies the ARNT and CYP1A1 expression and protects from BaP toxicity.

Effects of meal composition and meal timing on the expression of genes involved in hepatic drug metabolism in rats

Introduction

With chronotherapy, drug administration is synchronized with daily rhythms in drug clearance and pharmacokinetics. Daily rhythms in gene expression are centrally mastered by the suprachiasmatic nucleus of the hypothalamus as well as by tissue clocks containing similar molecular mechanisms in peripheral organs. The central timing system is sensitive to changes in the external environment such as those of the light-dark cycle, meal timing and meal composition. We investigated how changes in diet composition and meal timing would affect the daily hepatic expression rhythms of the nuclear receptors PXR and CAR and of enzymes involved in P450 mediated drug metabolism, as such changes could have consequences for the practice of chronotherapy.

Materials and methods

Rats were subjected to either a regular chow or a free choice high-fat-high-sugar (fcHFHS) diet. These diets were provided ad libitum, or restricted to either the light phase or the dark phase. In a second experiment, rats had access to chow either ad libitum or in 6 meals equally distributed over 24 hours.

Results

Pxr, Alas1 and Por displayed significant day-night rhythms under ad libitum chow fed conditions, which for Pxr was disrupted under fcHFHS diet conditions. Although no daily rhythms were detected in expression of CAR, Cyp2b2 and Cyp3a2, the fcHFHS diet did affect basal expression of these genes. In chow fed rats, dark phase feeding induced a diurnal rhythm in Cyp2b2 expression while light phase feeding induced a diurnal rhythm in Car expression and completely shifted the peak expression of Pxr, Car, Cyp2b2, Alas1 and Por. The 6-meals-a-day feeding only abolished the Pxr rhythm but not the rhythms of the other genes.

Conclusion

We conclude that although nuclear receptors and enzymes involved in the regulation of hepatic drug metabolism are sensitive to meal composition, changes in meal timing are mainly effectuated via changes in the molecular clock.

Chronopharmacology of anti-convulsive therapy

Approximately one-third of patients with epilepsy continue to have seizures despite antiepileptic therapy. Many seizures occur in diurnal, sleep/wake, circadian, or even monthly patterns. The relationship between biomarkers and state changes is still being investigated, but early results suggest that some of these patterns may be related to endogenous circadian patterns whereas others may be related to wakefulness and sleep or both. Chronotherapy, the application of treatment at times of greatest seizure susceptibility, is a technique that may optimize seizure control in selected patients. It may be used in the form of differential dosing, as preparations designed to deliver sustained or pulsatile drug delivery or in the form of 'zeitgebers' that shift endogenous rhythms. Early trials in epilepsy suggest that chronopharmacology may provide improved seizure control compared with conventional treatment in some patients. The present article reviews chronopharmacology in the treatment of epilepsy as well as future treatment avenues.

Chronobiology of epilepsy: diagnostic and therapeutic implications of chrono-epileptology

The combination of chronobiology and epilepsy offers novel diagnostic and therapeutic management options. Knowledge of the interactions between circadian periodicity, entrainment, sleep patterns, and epilepsy may provide additional diagnostic options beyond sleep deprivation and extended release medication formulations. It may also provide novel insights into the physiologic, biochemical, and genetic regulation processes of epilepsy and the circadian clock, rendering new treatment options. Temporal fluctuations of seizure susceptibility based on sleep homeostasis and circadian phase in selected epilepsies may provide predictability based on mathematical models. Chrono-epileptology offers opportunities for individualized patient-oriented treatment paradigms based on chrono-pharmacology, differential medication dosing, chrono-drug delivery systems, and utilization of "zeitgebers" such as chronobiotics or light-therapy and desynchronization strategies among others.

The influence of circadian rhythms on the kinetics of drugs in humans

In clinical practice, it is important to consider circadian rhythms in pharmacokinetics and cell responses to therapy in order to design proper protocols for drug administration. Scientists have arrived at this conclusion after several experiments in animals and in humans have clearly demonstrated that all organisms are highly organised according to circadian rhythms. These temporal cycles influence different physiological functions and, consequently, can influence the pharmacokinetic phases of drugs. A drug's pharmacokinetics can be modified according to the time of drug administration. In fact, the circadian changes of > 100 different compounds have been documented. The results obtained have led several scientific societies to provide guidelines concerning the timing of drug dosing for anticancer, cardiovascular, respiratory, anti-ulcer, anti-inflammatory, immunosuppressive and antiepileptic drugs. Absorption may be influenced by circadian rhythms and most lipophilic drugs seem to be absorbed faster when the drug is taken in the morning compared with the evening; for water-soluble compounds, no circadian variation in the absorption of drugs has been found. Concerning drug distribution, the higher the blood flow fraction an organ receives, the higher the rate constant for transferring drugs out of the capillaries. This drug pharmacokinetic phase may be influenced by circadian variations in the protein binding of acidic and basic drugs. Drug metabolism may be influenced by daily modifications of blood flow. For drugs with a high extraction ratio, metabolism depends on hepatic blood flow, while that of drugs with a low extraction ratio depends on liver enzyme activity. Hepatic blood flow has been shown to be greatest at 8 am and metabolism seems to be reduced during the night. Finally, concerning drug elimination, the clearance of 'flow-limited' drugs that present a high extraction rate is affected by the blood flow delivered to the organ, independent of the cardiac output fraction supplied. Chronopharmacokinetics can explain individual differences in drug levels revealed by therapeutic drug monitoring and can be used to optimise the management of patients receiving drug therapy.

Chronopharmacokinetics of ciclosporin and tacrolimus

The correct use of immunosuppressive drugs has a considerable influence on the prognosis of patients with organ transplants. The appropriate utilisation of the drugs involves the administration of an adequate dosage to reach the blood concentrations that will suppress the alloimmune response, while avoiding secondary toxicities. However, transplanted patients exhibit heterogeneous immunological responses and high inter- and intraindividual pharmacokinetic variabilities. One cause of these variabilities that is rarely considered is circadian rhythms. In vitro and in vivo experiments have clearly demonstrated that all organisms are highly organised according to an internal biological clock that influences various physiological functions. Considering that the absorption, distribution, metabolism and elimination of drugs is influenced by the physiological functions of the body, it is not surprising that the pharmacokinetic, and consequently the pharmacodynamic, profiles of drugs can be influenced by circadian rhythms. Ciclosporin, a mainstay immunosuppressive drug used following organ transplantation, displays minimum blood concentration (C(min)), maximum blood concentration (C(max)) and area under the blood concentration-time curve (AUC) in the morning that are generally higher than the corresponding parameters in the evening. These observations are supported by the ciclosporin total body clearance and elimination half-life in the morning, which are, on average, higher and shorter, respectively, than those in the evening. In addition, the disposition of tacrolimus is determined by the time of administration. The tacrolimus C(max) and AUC after the morning dose are significantly higher than those after the evening dose. Finally, the results reported in this review suggest considering more carefully the chronopharmacokinetics of tacrolimus and ciclosporin in order to obtain better results with fewer adverse effects. Significantly, the morning appears to be the best time for therapeutic monitoring using the C(min), C(max), concentration at 2 hours after dosing and AUC to modify dosages of tacrolimus and ciclosporin. Less certain are any conclusions about whether, in order to obtain better immunosuppressive control, higher doses must be administered when these drugs are given in the evening to compensate for the higher levels of interleukin-2.

[Development of new chronopharmacotherapies based on biological rhythm]

The mammalian circadian pacemaker resides in the paired suprachiasmatic nuclei (SCN). Clock genes are the genes that control the circadian rhythms of physiology and behavior. The effectiveness and toxicity of many drugs vary depending on dosing time associated with 24-h rhythms of biochemical, physiological, and behavioral processes under the control of the circadian clock. However, many drugs are still administered without regard to the time of day. Identification of a rhythmic marker for selecting dosing time will lead to improved progress and diffusion of chronopharmacotherapy. The monitoring of rhythmic markers may be useful in choosing the most appropriate time of day for administration of drugs and may increase their therapeutic effects and/or reduce their side effects. On the other hand, several drugs can cause alterations in 24-h rhythms, leading to illness and altered homeostatic regulation. Here, we show the disruptive effect of interferon on the rhythm of locomotor activity, body temperature, and clock gene mRNA expression in the periphery and SCN. The alteration of the clock function, a new concept of adverse effects, can be overcome by devising a dosing schedule that minimizes adverse drug effects on clock function. Furthermore, to produce new rhythmicity by manipulating the conditions of living organs using rhythmic administration of altered feeding schedules or several drugs appears to lead to the new concept of chronopharmacotherapy. One approach to increasing the efficiency of pharmacotherapy is administering drugs at times during which they are best effective and/or tolerated.

Valproic acid has temporal variability in urinary clearance of metabolites

The reasons for the intra- and interindividual variability in the clearance of valproic acid (VPA) have not been completely characterized. The aim of this study was to examine day-night changes in the clearance of 3-oxovalproate (3-oxo-VPA), 4-hydroxy-valproate (4-OH-VPA), and valproic acid glucuronides under steady state. Six diurnally active healthy male volunteers ingested 200 mg sodium valproate 12 hourly, at 0800 and 2000, for 28 days. On the last study day, two sequential 12-h urine samples were collected commencing at 2000 the evening before. Plasma samples were obtained at the end of each collection. Following alkaline hydrolysis, urine was analyzed for concentrations of VPA, 3-oxo-VPA, and 4-OH-VPA. A separate aliquot was assayed for creatinine (CR). The plasma concentrations of VPA, 3-oxo-VPA, 2-en-VPA, and CR were determined. The analysis of VPA and its metabolites was performed by GC-MS. There was an increase in plasma 3-oxo-VPA concentration at 0800, sampling as compared to 2000 sampling (p < .05). The urinary excretion of 3-oxo-VPA and VPA glucuronides were decreased between 2000 and 0800, compared to between 0800, and 2000, by 40% and 50% respectively (p < .05). These results indicate a nocturnal decrease in renal clearance of 3-oxo-VPA rather than a decrease in the beta-oxidation of VPA at night. These differences were not explained by differences between the sampling periods in CR excretion. These results indicate the importance of collecting samples of 24-h duration when studying metabolic profiles of VPA.

Influences of biological rhythms on the effects of psychotropic drugs

The efficacy of psychotropic drugs varies depending on the time of administration. This phenomenon is observed with antipsychotics, antidepressants, mood stabilizers, benzodiazepines, barbiturates, and psychostimulants. The presence or absence of this phenomenon and the rhythm phase in the efficacy of each drug varies depending on the drug, dose, parameter measured, animal species, and strain. A recent study demonstrating circannual changes in the phases of circadian rhythm of drug efficacy suggests that discrepancies between studies may be considerably explained by the presence of a circannual rhythm. The rhythms in drug effects are suggested not to be due to rhythmic changes in the pharmacokinetics of the drugs but rather to an endogenous rhythm in drug susceptibility resulting from a circadian rhythm in the intracerebral neurotransmission system. The presence of this phenomenon and its law have been demonstrated to a considerable extent in animals, but corresponding clinical reports in humans remain insufficient despite its clinical importance. Further study in humans is certainly warranted.

Chronotoxicity of sodium valproate in pregnant mouse and embryo

The influence of dosing time on the embryotoxicity of sodium valproate (valproic acid, VPA) was investigated in ICR mice under a light-dark (12:12) cycle. A significant circadian rhythm was shown for VPA-induced embryotoxicity, with the highest value at 1700 and the lowest at 0100. A similar pattern of rhythm was also shown for VPA-induced toxicity in pregnant and nonpregnant mice. No significant dosing time-dependent difference between injection at 1700 and 0100 was demonstrated for VPA concentrations in the embryo, plasma and brain. The rhythm in the embryotoxicity seems to be related to the rhythm in the sensitivity of the embryo and dam to the drug. Embryotoxicity and VPA concentrations were significantly higher on gestational day 13 than day 7. The pharmacokinetics of VPA contribute, at least partly, to the gestational stage-dependent embryotoxicity of VPA. The timing of drug administration (i.e., gestational stage and circadian phase) appears to be essential for studies on the embryotoxicity of VPA in mice.

Chronopharmacological study of acetylsalicylic acid in mice

Influence of dosing time on pharmacological effects and toxicity of acetylsalicylic acid was investigated in ICR male mice under light-dark (12:12) cycle. Significant circadian rhythms (day-night rhythms) were demonstrated for hypothermal and analgesic effects at 1 h after an injection of acetylsalicylic acid (200 mg/kg, i.p.) (P < 0.01, respectively). The rhythmic patterns of acetylsalicylic acid induced analgesia and hypothermia resembled overall the rhythms occurring in the non-drugged state. Injection of acetylsalicylic acid resulted in a parallel increase in latency to hot plate and a parallel decrease in rectal temperature. The relationship between plasma salicylate concentrations and responses was not clear. There was also a significant circadian rhythm in acetylsalicylic acid (850 mg/kg, i.p.) induced toxicity with the highest mortality at 17:00 and the lowest one at 05:00 (P < 0.05). Dosing time dependent kinetics of salicylate seems to be related to the rhythm of toxicity of the drug. The time in circadian stage at which acetylsalicylic acid is administered is essentially important in the actions of acetylsalicylic acid.

Pharmacokinetics of valproate after multiple-dose oral and intravenous infusion administration: gastrointestinal-related diurnal variation

A randomized, crossover study was conducted in healthy male volunteers to assess the diurnal variation in the steady-state pharmacokinetics of valproate after multiple 250-mg oral and intravenous infusion doses after an intravenous 750-mg loading dose. Multiple blood samples were collected throughout each 168-hour study period, and plasma valproate concentrations were quantitated using a gas chromatographic technique. Within-regimen comparisons indicated statistically significant differences for mean steady-state peak (Cmax) and trough (Cmin) plasma concentrations and area under the plasma concentration-versus-time curve (AUC) between the second and third doses on day 4 after oral dosing, indicating a diurnal variation in the rate of valproate absorption from the delayed-release tablet preparation. Between-regimen steady-state comparisons of pharmacokinetic parameters revealed some significant differences in mean time to Cmax (Tmax), Cmax, Cmin, AUC, and total body clearance for respective day-4 dosing intervals, but not for the entire day 4, except for Cmin and Tmax. Mean elimination rate constant and half-life did not significantly differ between the regimens. The regimens were bio-equivalent at steady state, as assessed by 90% confidence intervals (two one-sided test procedures) for Cmax, Cmin, and AUC, with similarity in degrees of fluctuation ((Cmax-Cmin)/Caverage). Despite the presence of diurnal variation in valproate absorption after oral dose administration, the steady-state plasma concentration-versus-time profile was well maintained by both regimens within the accepted therapeutic range of 50 to 100 micrograms/mL.

Effects of OM-853, a novel indolonaphthyridine derivative, on behavioral responses in the forced swim test in rats

Effects of OM-853 on behavioral responses in the forced swim test were studied. OM-853 significantly reduced the duration of immobility without any change in the exploratory activity. Imipramine also reduced the duration of immobility, but idebenone did not. On the other hand, vinpocetine enhanced the duration with a suppressive effect on ambulation. The anti-immobility effect of OM-853 was reversed by pretreatment with haloperidol. These results demonstrate that the effect of OM-853 on the swim test is different from that of idebenone and vinpocetine. Furthermore, the present results suggest that OM-853 may exert its anti-immobility activity through facilitated transmission of the dopaminergic and/or adrenergic systems.