Circadian variations in cyclosporine C2 concentrations during the first 2 weeks after liver transplantation

Effects of diurnal variation of bile acids by meal on cyclosporine A absorption

BACKGROUND

Stabilizing blood levels with microemulsified cyclosporine A (CsA), administered in many pediatric kidney diseases, is important for effective immunosuppression and reduced nephrotoxicity. CsA is affected by total bile acids (TBAs); however, no reports have simultaneously measured both. We aimed to elucidate the hypothesized relationship between TBA levels and diurnal variation in CsA in children.

METHODS

We retrospectively reviewed the medical records of children who were taking oral CsA for the treatment of kidney diseases between January 2016 and July 2021. They consumed four balanced meals and snacks during the day. CsA and TBA were measured twice, in pairs, before and at 0.5, 1, 1.5, 2, 3, and 4 h after oral administration in the morning and evening, and the four-h area under curve (AUC)_0-4 of CsA and trough-to-peak ratio (TPR) of TBA were compared.

RESULTS

Fifty-eight pairs were measured in total; 12 children had idiopathic nephrotic syndrome and 4 children had immunoglobulin A vasculitis with nephritis. The median age at measurement was 7.5 years and the dose of CsA was 3.8 mg/kg/day. The AUC_0-4 (ng·h/mL) was significantly lower in the evening than in the morning (1,669 vs. 1,451, P < 0.001). The TPR of TBA was significantly higher in the evening than in the morning (0.14 vs. 0.25, P < 0.001).

CONCLUSIONS

The low AUC_0-4 and slow TBA secretion observed in the evening may be due to pediatric-specific dietary rhythms; thus, snack timing should be considered in children for stabilizing CsA levels.

Chronopharmacology in Therapeutic Drug Monitoring-Dependencies between the Rhythmics of Pharmacokinetic Processes and Drug Concentration in Blood

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.

Effect of MDR1 C1236T polymorphism on cyclosporine pharmacokinetics: A systematic review and meta-analysis

BACKGROUND

Cyclosporine (CsA) is one of the immunosuppressive drugs, whose pharmacokinetic characteristics vary greatly among individuals. The published data reveal conflicting effects of the polymorphism of MDR1 exon 12 SNP C1236T on the pharmacokinetics of cyclosporine.This study aims to conduct a meta-analysis to investigate the effect of SNP C1236T on the pharmacokinetics of cyclosporine.

METHODS

A literature retrieval was conducted to find the relevant papers in databases including PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wan Fang Database (Wan Fang), Chinese Biomedical Literature Database (CBM), VIP Database for Chinese Technical Periodicals (VIP) electronic source for published studies until January 2017. The pharmacokinetic parameters, including C0 (trough blood concentration), C2 (whole-blood levels at 2 hours after drug intake), Cmax (the maximum concentration), and daily dose were extracted and a meta-analysis was performed by RevMan 5.3.

RESULTS

A total of 11 papers concerning 1361 individuals were included in the meta-analysis. As for dose adjusted C0, the results showed difference between subjects carrying CC genotypes and TT genotypes (MD: 6.76, 95% CI [2.38, 11.14], P = .02]. As for C2, the results showed significant difference between subjects carrying CC genotypes and CT genotypes (MD: -18.50, 95% CI [-35.49, -1.52], P = .03), as well as CC genotypes and TT genotypes (MD: -19.01, 95% CI (-35.85, -2.16), P = .03). As for Cmax, daily dose, and C0, the overall results showed no major influence.

CONCLUSIONS

MDR1 C1236T polymorphism may have a minor effect on cyclosporine pharmacokinetics in transplantation patients.

Chronotherapy: Intuitive, Sound, Founded…But Not Broadly Applied

Circadian rhythms are a collection of endogenously driven biochemical, physiological, and behavioral processes that oscillate in a 24-h cycle and can be entrained by external cues. Circadian clock molecules are responsible for the expression of regulatory components that modulate, among others, the cell’s metabolism and energy consumption. In clinical practice, the regulation of clock mechanisms is relevant to biotransformation of therapeutics. Accordingly, xenobiotic metabolism and detoxification, the two processes that directly influence drug effectiveness and toxicity, are direct manifestations of the daily oscillations of the cellular and biochemical processes taking place within the gastrointestinal, hepatic/biliary, and renal/urologic systems. Consequently, the impact of circadian timing should be factored in when developing therapeutic regimens aimed at achieving maximum efficacy, minimum toxicity, and decreased adverse effects in a patient. However, and despite a strong mechanistic foundation, only 0.16 % of ongoing clinical trials worldwide exploit the concept of ‘time-of-day’ administration to develop safer and more effective therapies. In this article, we (1) emphasize points of control at which circadian biology intersects critical processes governing treatment interventions; (2) explore the extent to which chronotherapeutics are incorporated into clinical trials; (3) recognize roadblocks; and (4) recommend approaches to precipitate the integration of chronobiological concepts into clinical practice.

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.

Suitable whole blood levels 2 hours after neoral in liver transplant patients: experiences at a single center

Whole blood levels 2 hours after Neoral (C2) administration were observed to correlate better with area under the curve (AUC(0-4)) than trough levels (C0), suggesting that C2 may be the best single time point predictor of Neoral absorption. Owing to concerns about drug toxicity due to excessive immunosuppression, C2 adjustments to target blood levels may represent an advance. The present study measured C2 and levels to determine which correlated more closely with AUC(0-4).

METHODS

Between August 2003 and July 2004, 40 adult liver transplantations were performed in our center. All patients received Neoral twice daily. They were maintained at a C0 level of about 200 ng/mL. C0 levels were measured daily. C2 levels were estimated on postoperative days 3, 5, 7, 14, and 28. AUC(0-4) performed on postoperative days 3, 7, and 28 was calculated using the trapezoidal rule.

RESULTS

The mean AUC(0-4), C0, C1, C2, C3, and C4 were 1100.3 +/- 484.8 ng/mL, 197.1 +/- 84.7 ng/mL, 240.7 +/- 166.2 ng/mL, 307.8 +/- 162.6 ng/mL, 302.8 +/- 138.9 ng/mL, and 300.3 +/- 142.8 ng/mL, respectively. C2 correlated with AUC(0-4) (R2 = 0.868: P < .05) better than C0 (R2 = 0.245: P < .05), C1 (R2 = 0.604: P < .05), or C4 (R2 = 0.583: P < .05).

CONCLUSIONS

Neoral dose monitoring according to a mean C2 range of 307.8 +/- 162.6 ng/mL correlated better with AUC(0-4). Further studies are required to determine suitable C2 levels in liver transplant patients.

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.

Large within-day variation in cyclosporine absorption: circadian variation or food effect?

With the recent focus of monitoring cyclosporine (CsA) therapy using measures of CsA absorption, it is important to understand published reports of diurnal variation in CsA exposure. In 10 renal transplant patients, CsA concentrations were measured 0, 1, 2, 3, and 4 h after both the morning and the evening doses and in a repeat session at least 1 wk later. Both area under the curve for the final 4 h after cyclosporine dose and cyclosporine concentrate 2 h after the cyclosporine dose were more than two-fold higher after the morning dose in both sessions. Because the morning levels were collected in a fasted condition and the evening ones in a fed condition, the study was extended to collect evening levels after fasting. The area under the curve for the final 4 h after cyclosporine dose and cyclosporine concentrate 2 h after the cyclosporine dose values observed now were comparable to the morning fasted values. That the large diurnal variation was due to variation in food consumption, as opposed to a biologic circadian rhythm affecting CsA absorption, has significant implications for therapeutic drug monitoring.

Effect of age, ethnicity, and glucocorticoid use on tacrolimus pharmacokinetics in pediatric renal transplant patients

Tacrolimus has become an effective alternative to cyclosporine as a component of primary immunosuppression in pediatric renal transplant patients, but the information on the pharmacokinetic characteristics of tacrolimus in young patients is still limited. The primary objective of this study was to determine the effect of patient age, ethnicity, and concurrent steroid administration on tacrolimus pharmacokinetics in pediatric renal transplant patients. The study population consisted of 30 pediatric patients, age 1.5-18.6 yr, who received a kidney transplant between July 1999 and February 2004. After twice daily dosing was stabilized based on clinical judgment, at least 5 days postoperatively, tacrolimus levels were drawn prior to, and 1, 2, 4, 8, and 12 h after the morning dose. The mean dose of tacrolimus was 0.12 mg/kg/dose. Mean trough level was 11.9 +/- 5.0 ng/mL. Mean area under the curve (AUC) was 192 +/- 84 with a range of 78-360 h x (ng/mL). The correlation between trough level and AUC was only fair (r = 0.74); later time points correlated better with AUC, and an excellent correlation (r = 0.96) was obtained between the mean of trough and 2-h level (C(2)) and AUC. There was a negative correlation between age and dose per body weight (r = -0.68). African-American patients had marginally lower drug exposure with similar dosing. Three age groups (<5, 5-12, and >12 yr) were compared with respect to dosing and AUC. Despite similar AUC in all three groups, the mean dose per kg required to achieve the AUC was 2.7- and 1.9-fold higher in the <5 and 5-12-yr groups, respectively, compared with the >12-yr group. Nine of the 30 patients were on a totally steroid-free regimen. Their tacrolimus dose and trough levels were similar to those of steroid-exposed patients, but their mean AUC was 41% higher. Our results show an inverse correlation between age and required tacrolimus dose, wide interindividual variation, and greater exposure with steroid-free regimen despite no change in trough level.

History of C2 monitoring in heart and liver transplant patients treated with cyclosporine microemulsion

Therapeutic drug monitoring of CsA has evolved since the introduction of CsA microemulsion. The purpose of the present review is to summarize the history of CsA concentration 2 hours postdose (C2) monitoring in heart and liver transplantation. C2 has been shown to be the best single time point that correlates with the area-under-the-curve, with a correlation coefficient (r2) ranging between .83 and.93. C2 monitoring (300 to 600 ng/mL) has resulted in a significant clinical benefit in long-term heart and liver transplant patients compared to trough level (C0) monitoring. Moreover, a C2 range of 300 to 600 ng/mL resulted in a similar calcineurin inhibition compared to a C2 range of 700 to 1000 ng/mL or a C0 range of 100 to 200 ng/mL while being less injurious to renal function. In de novo liver transplant patients not receiving induction therapy, the achievement of a target C2 of 850 to 1400 ng/mL by postoperative day 3 has resulted in a low acute rejection rate. Furthermore, C2 monitoring has been associated with a lower rejection rate in hepatitis C virus (HCV)-negative patients and with an overall lesser severity of acute rejection compared to C0 monitoring. In de novo heart transplant patients who receive antithymocyte globulin induction, a lower C2 range may be sufficient to prevent rejection and renal dysfunction. Future studies should help to fine-tune the optimal C2 range in heart or liver transplant patients receiving induction therapy and different maintenance immunosuppressive combinations.

Experience with cyclosporine

The concentration at 2 hours after drug intake (C2) is proposed to optimise clinical outcomes in organ transplantation and for adjustment of the regimen of cyclosporine. A population based pharmacokinetic study was undertaken during the first 30 days post-liver transplantation. Preliminary results observed during this study on C0 and C2 values are described here. Thirty-seven patients with first hepatic transplantation were included in a single center, prospective study conducted under conditions of normal practice. Dose adjustments were made according to C0. Cyclosporine C0 and C2 were assayed by an immunoassay (EMIT) and by a HPLC technique. Clinical outcome was assessed by occurrence and severity of acute rejection. Our data shows that average blood C0 and C2 concentrations are significantly different with the two techniques. From the third day to the end of the study, mean C2 (EMIT) were within or near the recommended values. This was associated with a low rejection rate (8.8%). Nevertheless, individual values are largely dispersed and low cyclosporine absorption profiles are identified. Mean cyclosporine dose was low compared to a previous study (7.65 +/- 4.28 mg/kg/day). Our data suggest that the target ranges need to be adjusted when different techniques are applied and that optimal cyclosporine regimen to achieve the C2 goal and low rejection rate remains to be defined. Pharmacokinetic models based on population study are needed to describe normal and abnormal cyclosporine absorption profiles with higher accuracy.