Dependency of cyclosporine tissue distribution and metabolism on the age and gender of rats after a single intravenous dose

Skeletal muscle ischemia-reperfusion injury and cyclosporine A in the aging rat

Old patients exhibit muscle impairments and increased perioperative risk during vascular surgery procedures. Although aging generally impairs protective mechanisms, data are lacking concerning skeletal muscle in elderly. We tested whether cyclosporine A (CsA), which protects skeletal muscle from ischemia-reperfusion (IR) in young rats, might reduce skeletal muscle mitochondrial dysfunction and oxidative stress in aging rats submitted to hindlimb IR. Wistar rats aged 71-73 weeks were randomized to IR (3 h unilateral tourniquet application and 2 h reperfusion) or IR + CsA (10 mg/kg cyclosporine IV before reperfusion). Maximal oxidative capacity (VM ax ), acceptor control ratio (ACR), and relative contribution of the mitochondrial respiratory chain complexes II, III, IV (VS ucc ), and IV (VTMPD /Asc ), together with calcium retention capacity (CRC) a marker of apoptosis, and tissue reactive oxygen species (ROS) production were determined in gastrocnemius muscles from both hindlimbs. Compared to the nonischemic hindlimb, IR significantly reduced mitochondrial coupling, VMax (from 7.34 ± 1.50 to 2.87 ± 1.22 μMO2 /min/g; P < 0.05; -70%), and VS ucc (from 6.14 ± 1.07 to 3.82 ± 0.83 μMO2 /min/g; P < 0.05; -42%) but not VTMPD /Asc . IR also decreased the CRC from 15.58 ± 3.85 to 6.19 ± 0.86 μMCa(2+) /min/g; P < 0.05; -42%). These alterations were not corrected by CsA (-77%, -49%, and -32% after IR for VM ax, VS ucc , and CRC, respectively). Further, CsA significantly increased ROS production in both hindlimbs (P < 0.05; +73%). In old rats, hindlimb IR impairs skeletal muscle mitochondrial function and increases oxidative stress. Cyclosporine A did not show protective effects.

Cyclosporine use in hematopoietic stem cell transplantation: pharmacokinetic approach

Cyclosporine is one of the most vital agents in the process of successful allogeneic hematopoietic stem cell transplantation. Despite a long history and worldwide extent of cyclosporine use for prevention of graft versus host disease, currently there are lots of uncertainties about its optimal method of application to reach the best clinical outcome. A major portion of this problem stems from complicated cyclosporine pharmacokinetics. Study of cyclosporine pharmacokinetic behavior can significantly help recognition of its effectiveness and consequently, optimization of dosing, administration, monitoring and management of adverse effects. In this review, highly accredited but sparse scientific data are gathered in order to provide a better insight for preparation of practice guidelines and directing future studies for allogeneic hematopoietic cell recipients.

Pharmacokinetic characterization of intravenous cyclosporine treatment for cardioprotection during resuscitation of asphyxiated newborn piglets

OBJECTIVES

Cyclosporine treatment, as a single intravenous bolus, during resuscitation has been shown to attenuate myocardial injury in asphyxiated newborn piglets. However, the pharmacokinetics of cyclosporine treatment for cardioprotection in newborns has not been studied. We aimed to assess the pharmacokinetics of a single intravenous cyclosporine treatment during resuscitation of asphyxiated newborn piglets and compare these parameters with healthy newborn piglets.

DESIGN

Newborn piglets were acutely instrumented and normocapnic alveolar hypoxia was induced for 2 hours followed by 4 hours of reoxygenation. Piglets were block-randomized to receive a single intravenous bolus of cyclosporine (2.5-25 mg/kg) (n = 8 per group). Eight piglets underwent no hypoxia-reoxygenation and received 10 mg/kg cyclosporine at the corresponding time point. Plasma cyclosporine and troponin concentrations during reoxygenation period were determined by high-pressure liquid chromatography and enzyme-linked immunosorbent assay, respectively. Noncompartmental methods were used to calculate the pharmacokinetic parameters. Cyclosporine concentrations and pharmacokinetic parameters were analyzed by one-way analysis of variance.

SETTING

University animal laboratory.

SUBJECTS

Piglets (1-4 days old, weighing 1.4-2.5 kg).

INTERVENTIONS

Intravenous cyclosporine (2.5, 10, or 25 mg/kg) given during resuscitation.

MEASUREMENTS AND MAIN RESULTS

In the hypoxic-reoxygenated piglets, the plasma AUC(0-4 hrs) and C(max) of cyclosporine at reoxygenation were in the following rank order: 25 > 10 > 2.5 mg/kg treatment (p < 0.001 between groups, analysis of variance). Plasma AUC(0-4 hrs) and C(max) in piglets treated with cyclosporine at 25 mg/kg was associated with increased plasma troponin levels, a marker of myocardial injury, relative to piglets treated with 2.5 and 10 mg/kg. Asphyxiated newborn piglets had higher clearance and lower AUC(0-∞), but similar AUC(0-4 hrs), steady-state volume of distribution, and mean residence time compared with those of healthy newborn piglets.

CONCLUSIONS

This is the first study to demonstrate the pharmacokinetics of intravenous cyclosporine treatment during resuscitation of asphyxiated newborn piglets, which did not appear to different from that of healthy piglets.

Gender- and dose-related effects of cyclosporin A on hepatic and bone metabolism

Previous data have shown gender-related differences in the skeletal effects of the immunosuppressive drug cyclosporin A (CsA) in rats. To test the hypothesis that the gender-related skeletal effects of CsA are caused by gender-specific metabolism of this drug, we treated aged male and female sham-operated, gonadectomized (GX) as well as sex hormone-supplemented GX rats with 5 mg/kg CsA three times per week for 2 months, and analyzed the bone phenotype as well as the concentrations of CsA and its major metabolites AM1, AM1c, AM9, and AM4N in blood, urine, and liver tissue. CsA treatment induced high turnover osteopenia in males, but not females. Male rats showed several-fold higher CsA and CsA metabolite blood levels compared with females. Renal clearance data revealed that CsA undergoes selective tubular reabsorption in male, but not female rats. However, a mathematical modeling approach demonstrated that the higher CsA blood levels in males were almost exclusively caused by a 6-fold lower hepatic clearance rate compared with females. In addition, we subcutaneously treated female rats with up to 6-fold higher doses of CsA. Similar to males, high dose CsA induced high turnover osteopenia in female rats. Our data show that the gender-related differences in the skeletal effects of CsA are caused by a higher hepatic clearance rate for CsA in female compared to male rats, and not by a differential skeletal response to CsA. Moreover, our study indicates that CsA blood levels of ≤200 ng/ml measured by HPLC do not induce high turnover osteopenia in aged rats.

Gender differences in pharmacokinetics of tacrolimus and their clinical significance in kidney transplant recipients

BACKGROUND

The possible influence of gender on tacrolimus disposition and response in kidney transplant recipients is an issue of medical importance.

OBJECTIVE

The aim of this study was to detect interpatient pharmacokinetic variability of tacrolimus due to patients' gender and to assess the predictability of individual tacrolimus concentrations using abbreviated AUC measurements. The secondary objective was to find the best sampling time to predict the exposure of tacrolimus in kidney transplant recipients.

METHODS

Gender-related first oral dose tacrolimus pharmacokinetics studies were conducted in 20 Serbian kidney transplant recipients (10 men/10 women) on quaternary immunosuppressive therapy. The first tacrolimus oral dose (0.05 mg/kg) was given on day 5 post-transplant. Blood concentrations were measured by microparticle enzyme immunoassay method. Associations between each sampling time point of concentrations and 12 hours after the administration AUC (AUC(0-12)) were evaluated by Pearson correlation coefficients. Abbreviated sampling equations were derived by multiple stepwise regression analyses.

RESULTS

AUC(0-12) showed remarkable interindividual variations after the first tacrolimus oral dose. There were significantly lower values of AUC in women than men (P < 0.05). The most important time point influencing AUC(0-12) was the concentration of tacrolimus measured 2 hours after administration(C(2)) in women, whereas in men the most important time points were the concentrations at 1 (C(1)), 4 (C(4)), and 12 (C(12)) hours as an abbreviated AUC.

CONCLUSION

Our results show significant differences between men and women. C(2) seems to be indicator of total body exposure to tacrolimus in the early period after kidney transplant in women. The three-point sampling method seems to be a good indicator of abbreviated AUC for a tacrolimus monitoring strategy in men.

Pharmacokinetics of cyclosporine A after massive hepatectomy: a hint for small-for-size graft in living donor liver transplantation

In living donor liver transplantation, graft size is very important, and various studies have been conducted regarding these problems in small-for-size (SFS) grafts. The administration of immunosuppressants for SFS graft, in which the functional liver mass is small and necessary for excessive liver regeneration, has not been reported so far. The aims of this study were to investigate the optimal administration of cyclosporine (CyA) and characteristics of metabolism of CyA, according to liver volume. Seven-week-old male Wister rats were randomly divided into four groups: two CyA-administered groups (CyA groups), 70% and 90% hepatectomy (Hx); and two control groups, 70% and 90% Hx. The 70% Hx and 90% Hx were used as the surrogate model of SFS for 30% and 10% graft models. In CyA groups, CyA (5 mg/kg/day) was given for 3 days before Hx and after surgery until sacrifice. Animals were sacrificed at 0, 12, 24, 48, and 72 hr after Hx. The blood concentration of CyA and the expression of the CYP3A2 gene were measured at each point in CyA groups, and liver regeneration was evaluated by measuring the ratio of remnant liver weight to body weight in each group. Regarding the blood concentration of CyA, no difference was recognized between 30% and 10% graft models except for 72 hr after Hx. As for liver regeneration, no significant difference was recognized. Regarding the expression of CYP3A2, no change was noted in the 30% graft model; on the other hand, CYP3A2 expression was reduced. Significant differences between the 30% and the 10% graft model were observed 48 and 72 hr after Hx. The blood concentration of CyA was not dependent on the volume of the liver graft.

Neoimmun versus Neoral: a bioequivalence study in healthy volunteers and influence of a fat-rich meal on the bioavailability of Neoimmun

In two crossover studies with 12 (6 males/6 females) healthy young volunteers each, we compared the bioavailability of Neoimmun capsules with the microemulsion Neoral and the influence of a fat-rich breakfast on the bioavailability of Neoimmun. Each volunteer received a single dose of 200 mg cyclosporine A in each period. Blood samples were taken up to 24 h and analysed for cyclosporine A by high-performance liquid chromatography (HPLC) and photometric detection. The pharmacokinetic parameters were determined by non-compartmental analysis. The treatments were tested for bioequivalence and significant differences. The bioavailability of Neoimmun was significantly lower compared to Neoral, albeit Neoimmun met the bioequivalence criterion (90% confidence interval of AUC 0.80-0.94) or missed the criterion only marginally (90% confidence interval of c (max) 0.75-0.91). The bioavailability of Neoimmun as determined by area under the blood concentration-time curve (AUC) increased by nearly 20% after a fat-rich breakfast. However, mean peak concentrations after food were only higher in male subjects, whereas mean peak concentrations in female subjects were lower compared to fasting administration. In conclusion, our data show that Neoimmun exhibits a lower bioavailability than the microemulsion Neoral and that food has a significant but variable and sex-dependent impact on the bioavailability of Neoimmun capsules.

Evaluation of performance factors affecting two formulations of cyclosporine in pediatric renal transplant patients

Success of renal transplantation in children is largely due to improvements in immunosuppressant therapy since the introduction of calcineurin inhibitors. The aim of this study was to identify possible factors that result in formulation differences in the exposure of pediatric patients to cyclosporine (CsA). We examined the handling of the two major formulations of CsA in a group of pediatric renal transplant recipients. The pharmacokinetic profiles of both formulations were assessed, and the data stratified to assess the effects of age, gender, time posttransplant, and other concomitant drug therapy on the two CsA formulations. The microemulsified formulation (MEC) enhanced bioavailability compared to the older oil-based formulation (CYA), especially at C2, with more predictable and consistent absorption in children. This higher bioavailability allowed a 15% reduction of dosing to achieve equal drug exposure. The concentration achieved by MEC at C2 demonstrated a much higher correlation with area under the concentration curve (AUC) than the concentration at C0. In the case of CYA a strong correlation was obtained between AUC and the concentrations obtained at both C0 and C2. Calcium channel blockers increased AUC(0-8) for both CsA formulations. Norfloxacin and pravastatin cotreatment had no effect on either of the CsA formulations. In contrast, the bioavailability of CsA was increased in boys using MEC formulation but this gender-based difference was absent during the use of CYA. This suggests that caution is required for introduction of new formulations of drugs to pediatric patients to evaluate differential effects of age, gender, and concomitant drug therapy.

Oral evaluation in rabbits of cyclosporin-loaded Eudragit RS or RL nanoparticles

The hydrophobic cyclic undecapeptide cyclosporin A (CyA) used in the prevention of graft rejection and in the treatment of autoimmune diseases was encapsulated by nanoprecipitation within non-biodegradable polymeric nanoparticles. The effect of polymers (Eudragit RS or RL) and additives within the alcoholic phase (fatty acid esters and polyoxyethylated castor oil) on the size, zeta potential and the encapsulation efficiency of the nanoparticles was investigated. The mean diameter of the various CyA nanoparticles ranged from 170 to 310 nm. The size as well as the zeta potential increased by adding fatty acid ester and polyoxyethylated castor oil within the organic phase. No significant differences in surface potential were observed for all formulations tested. Probably due to the very low water solubility of the drug, high encapsulation efficiencies were observed in a range from 70 to 85%. The oral absorption of CyA from these polymeric nanoparticles was studied in rabbits and compared to that of Neoral capsule. Based on comparison of the area under the blood concentration-time curve values, the relative bioavailability of CyA from each nanoparticulate formulation ranged from 20 to 35%.

Skeletal effects of cyclosporin A are gender related in rats

The immunosuppressive drug cyclosporin A (CsA) is thought to be involved in the pathogenesis of posttransplantation osteoporosis. To evaluate further the skeletal effects of CsA, we treated aged male and female sham-operated and gonadectomized rats with low doses of CsA for 4 months. Here, we show that CsA is antiresorptive and bone-sparing in aged female rats but increases bone resorption and reduces bone mass in aged male rats. However, even in male rats, CsA treatment, at clinically relevant doses, increased bone resorption only transiently and did not result in pronounced long-term cancellous bone loss. The gender-specific skeletal effects of CsA were not modulated by sex hormones or gonadectomy. CsA did not influence sex steroid metabolism in male or female rats. However, endogenous estradiol in sham-operated female rats (and especially, exogenous administration of 17beta-estradiol in ovariectomized rats) markedly diminished blood levels of CsA, probably by increasing hepatic CsA metabolism. Although the mechanism for the gender-specific skeletal effects of CsA is still obscure, our findings may have important implications for clinical therapy with CsA.

Pharmacokinetic and pharmacodynamic evaluation of cyclosporin A O/W-emulsion in rats

The pharmacokinetics and pharmacodynamics of the cyclosporin A (CSA) O/W-emulsion were studied after intravenous and oral administration to Sprague-Dawley rats. Two commercial products, CIPOL Inj. and Sandimmun Neoral, were used as the reference formulations. CSA concentration and lymphocyte populations in whole blood were measured by TDxFLx and Coulter STKS, respectively. The pharmacokinetic and pharmacodynamic parameters were obtained by fitting experimental data to two-compartment model and to indirect pharmacodynamic model, respectively, using WINNONLIN. The area under the concentration-time curve (AUC), terminal half-lives (T(1/2)), total clearance (CL(t)) and relative bioavailability (F) after intravenous administration of CSA O/W-emulsion were not significantly different from those of intravenous administration of CIPOL Inj. (P>0.05). In oral administration, AUC and C(max) of CSA O/W-emulsion were significantly decreased (P<0.05), while T(1/2), MRT, T(max) and F were not significantly different (P>0.05) from those of Sandimmun Neoral. However, the area between the baseline and effect curves (ABEC) and pharmacodynamic efficiency (EFF) of CSA O/W-emulsion were significantly greater than those of references regardless of routes of administration (P<0.05). The pharmacodynamic availability (F(PD)) of CSA O/W-emulsion was 1.79- and 2.13-fold higher than that of CIPOL Inj.and Sandimmun Neroal (P<0.05), respectively.

High-performance liquid chromatographic analysis of cyclosporin A in rat blood and liver using a commercially available internal standard

All the available HPLC assays of cyclosporin A (CyA) use internal standards that are not commercially available. Our purpose was to develop an HPLC assay for measurements of CyA in rat blood and liver using a commercially available internal standard (I.S.). After the addition of tamoxifen (I.S.), blood (0.25 ml) or the liver homogenate (1 ml) samples were extracted into a mixture of ether:methanol (95:5). The residue after evaporation of the organic layer was dissolved in 200 microl of an injection solution and washed with 1 ml of hexane before analysis. The separation was achieved using an LC-1 column (70 degrees C) with a mobile phase of methanol-acetonitrile-0.01 M KH(2)PO(4) (50:25:25, v/v) and a flow-rate of 1 ml/min. Detection was at 205 nm. Cyclosporin A and I.S. eluted at 5 and 7 min, respectively, free from endogenous peaks. Linear relationships (r>0.98) were observed between the CyA:I.S. peak area ratios and the CyA concentrations within the range of 0.2-10 microg/ml for blood and 0.1-4 microg/ml for the liver homogenates. The intra- and inter-run C.V.s and errors for both the blood and liver samples were <15%. The extraction efficiency (n=5) was close to 100% for both CyA and I.S. in both blood and liver homogenates. The lower limit of quantitation of the assay was 0.2 or 0.1 microg/ml based on 250 microl of blood or 1 ml of liver homogenate, respectively. The assay was capable of measuring blood and liver concentrations of CyA in a rat injected intravenously with a single 5-mg/kg dose of the drug.

Freeze-drying of polycaprolactone and poly(D,L-lactic-glycolic) nanoparticles induce minor particle size changes affecting the oral pharmacokinetics of loaded drugs

The present study was geared at identifying the conditions to stabilize poly (D,L-lactic-glycolic) (PLGA) and polycaprolactone (PCL) nanoparticles (NP) by freeze-drying with several cryoprotective agents. Differential scanning calorimetry and freeze-thawing studies were used to optimize the lyophilization process. These studies showed that all samples were totally frozen at -45 degrees C and evidenced the necessity of adding sucrose, glucose, trehalose or gelatine to preserve the properties of NP regardless of the freezing procedure. However, only 20% sucrose and 20% glucose exerted an acceptable lyoprotective effect on PLGA and PCL NP, respectively. Nonetheless, the final to initial size ratios ( approximately 1.5) indicated that particle size was slightly affected in both cases. In vivo studies with CyA-loaded PCL NP whose sizes matched those obtained after NP preparation (100 nm) and after being lyophilized (160 nm) showed that the changes of particle size might have some relevance on drug pharmacokinetics. The MRT was significantly (P<0.05) modified after an oral CyA dose of 5 mg/kg and the treatment with 160-nm sized CyA-loaded NP produced a higher drug partition into the liver of Wistar rats potentially affecting the toxic and immunosuppressive profile of the drug. Therefore, although the particle size changes induced by NP lyophilization were slight, they need to be carefully evaluated and cannot be neglected.