Cyclosporine Pharmacokinetic Parameters Research Articles

Pharmacokinetic interaction study of ticagrelor and cyclosporine in healthy volunteers.

Patients with acute coronary syndrome and certain co-morbidities may receive ticagrelor, a reversibly binding P2Y(12) receptor antagonist, and cyclosporine, a commonly used immunosuppressant drug. This study assessed the potential pharmacokinetic drug-drug interaction between ticagrelor and cyclosporine. In this single-centre, open-label, three-treatment, three-period crossover study (NCT01504906), healthy volunteers (n = 26) randomly received each of three treatments: cyclosporine (600 mg single oral dose) plus ticagrelor (180 mg single oral dose); cyclosporine alone; ticagrelor alone. Treatments were separated by a washout period of ≥14 days. Plasma concentrations of ticagrelor and its active metabolite (AR-C124910XX) and blood concentrations of cyclosporine were analyzed, and pharmacokinetic parameters were calculated. Safety and tolerability were assessed. Compared with ticagrelor alone, the geometric least squares mean (LSM) ratio (90 % confidence interval [CI]) for the ticagrelor area under the plasma concentration-time curve from time zero to infinity (AUC(∞)) was 2.83 (2.63-3.06), and the maximum plasma concentration (C(max)) was 2.30 (2.06-2.58), in the presence of cyclosporine. Co-administration of cyclosporine with ticagrelor significantly increased AR-C124910XX AUC(∞) (1.33 [1.23-1.42]) and decreased C(max) (0.85 [0.76-0.94]). Ticagrelor had no effect on cyclosporine pharmacokinetic parameters, as the 90 % CIs of the LSM ratios were all within the 0.80-1.25 no-effect range. Co-administration of ticagrelor and cyclosporine was generally well tolerated. Co-administration of cyclosporine with ticagrelor increased exposure to ticagrelor and its active metabolite and had no effect on cyclosporine pharmacokinetic parameters. The magnitude of cyclosporine's effect on ticagrelor pharmacokinetics does not warrant dose adjustment of ticagrelor.

CYP3A5 Polymorphism Effect on Cyclosporine Pharmacokinetics in Living Donor Renal Transplant Recipients: Analysis by Population Pharmacokinetics

Cyclosporine is often used to prevent allograft rejection in renal transplant recipients. However, cyclosporine has a narrow therapeutic window and large variability in its pharmacokinetics. Individual characteristics and genetic polymorphisms can cause the variation. Hence, it is important to determine the cause(s) of the variation in cyclosporine pharmacokinetics. To our knowledge, this is the first reported population pharmacokinetic study of cyclosporine in living donor renal transplant recipients that considered the genetic polymorphism as a covariate. To build a population pharmacokinetic model of cyclosporine in living donor renal transplant recipients and identify covariates including CYP3A5*3, ABCB1 genetic polymorphisms that affect cyclosporine pharmacokinetic parameters. Clinical characteristics and cyclosporine concentration data for 69 patients who received cyclosporine-based immunosuppressive therapy after living donor renal transplantation were collected retrospectively for up to 400 postoperative days. CYP3A5*1/*3 and ABCB1C1236T, G2677T/A, C3435T geno-typing was performed. A population pharmacokinetic analysis was conducted using a NONMEM program. After building the final model, 1000 bootstrappings were performed to validate the final model. In total, 2034 blood samples were collected. A 1-compartment open model with first-order absorption and elimination was chosen to describe the pharmacokinetics of cyclosporine. A population pharmacokinetic analysis showed that postoperative days, sex, and CYP3A5 genotype significantly affected the pharmacokinetics of cyclosporine. The final estimate of mean clearance was 56 L/h, and the mean volume of distribution was 4650 L. The interindividual variability for these parameters was 22.98% and 51.48%, respectively. Using the present model to calculate the dose of cyclosporine with CYP3A5 genotyping can be possible for the patients whose cyclosporine concentration is not within the therapeutic range even with therapeutic drug monitoring.

Population Pharmacokinetics of Cyclosporine in Korean Adults Undergoing Living‐Donor Kidney Transplantation

To estimate the population pharmacokinetic parameters of cyclosporine in Korean adults undergoing living-donor kidney transplantation, and to identify clinical factors affecting cyclosporine pharmacokinetics. Retrospective cohort study. Single, 1600-bed, tertiary care academic medical center in Seoul, South Korea. Seventy-four living-donor kidney transplant recipients (mean age 42 yrs) receiving oral cyclosporine microemulsion as an immunosuppressant between January 1, 2001, and August 31, 2006. Using nonlinear mixed-effects modeling (NONMEM) with first-order absorption and elimination, a total of 2394 whole-blood cyclosporine concentrations from the 74 patients were analyzed. The effects of several clinical covariates on cyclosporine pharmacokinetic parameters were evaluated over 12 months after transplantation. The absorption rate constant was fixed at 1.28 hour(-1), and the following population pharmacokinetic estimates were calculated: cyclosporine clearance 43.6 L/hour, apparent volume of distribution 1990 L, and interpatient variability for clearance (coefficient of variation) 17.69%. The clinical factors (covariates) that significantly affected cyclosporine pharmacokinetics were postoperative days, prednisolone dose (in mg/day), total bilirubin level (mg/dl), current body weight (in kg), and concurrent use of amlodipine. This population pharmacokinetic model identified important sources of variability in cyclosporine pharmacokinetics. The model will help calculate cyclosporine dose requirements in renal transplant recipients according to specific clinical factors affecting cyclosporine clearance, and it will also be useful for therapeutic drug monitoring.

Frequencies and roles of CYP3A5, CYP3A4 and ABCB1 single nucleotide polymorphisms in Italian teenagers after kidney transplantation

The main genes involved in the pharmacokinetics of immunosuppressive drugs are those encoding cytochrome P450 (CYP) family enzymes and multidrug resistance 1 (ABCB1). In this study, 87 Italian teenagers with transplanted kidneys (mean age 11.6±4.8 years) receiving calcineurin inhibitors (CNIs) were genotyped for the single nucleotide polymorphisms (SNPs) CYP3A5*1/3 and CYP3A4*1B for CYP3A, and C1236T, G2677T/A, C3435T and IVS21+49 for ABCB1, and retrospectively evaluated for the influence of the screened SNPs on CNI blood level at different post-transplantation times. The CYP3A5*1 allele was present in 7% of the patients, and the CYP3A4*1B allele was present in 3% of patients. The ABCBl C1236T, G2677T/A and C3435T SNPs C, G and T occurred frequently (55%, 53% and 54%, respectively). The frequency of the T allele of IVS21+49 was 86%. The frequency of SNPs in both genes was comparable with that reported in other European Caucasian populations but different from that found in Asians or Afro-Americans. None of the cyclosporine (CsA) pharmacokinetic parameters were associated with the CYP3A5 genetic polymorphism, whereas the presence of the A allele in some patients was responsible for the required administration of a significantly increased dose of tacrolimus (Tac) that was necessary to reach therapeutic target levels. None of the Tac pharmacokinetic parameters were associated with ABCB1 SNPs, but ABC1 SNPs had early effects on the CsA exposure index and dose requirements. In conclusion, because SNPs of the CYP3A and ABCB1 genes may be associated with CNI pharmacokinetic parameters and exposure indices, pre-transplant genetic screening should be considered in order to avoid immunosuppressant-related adverse events.

P.1.e.006 Regional increase in P-glycoprotein function in the blood-brain-barrier of patients with chronic schizophrenia

The main genes involved in the pharmacokinetics of immunosuppressive drugs are those encoding cytochrome P450 (CYP) family enzymes and multidrug resistance 1 (ABCB1). In this study, 87 Italian teenagers with transplanted kidneys (mean age 11.6 ± 4.8 years) receiving calcineurin inhibitors (CNIs) were genotyped for the single nucleotide polymorphisms (SNPs) CYP3A5*1/3 and CYP3A4*1B for CYP3A, and C1236T, G2677T/A, C3435T and IVS21+49 for ABCB1, and retrospectively evaluated for the influence of the screened SNPs on CNI blood level at different post-transplantation times. The CYP3A5*1 allele was present in 7% of the patients, and the CYP3A4*1B allele was present in 3% of patients. The ABCBl C1236T, G2677T/A and C3435T SNPs C, G and T occurred frequently (55%, 53% and 54%, respectively). The frequency of the T allele of IVS21+49 was 86%. The frequency of SNPs in both genes was comparable with that reported in other European Caucasian populations but different from that found in Asians or Afro-Americans. None of the cyclosporine (CsA) pharmacokinetic parameters were associated with the CYP3A5 genetic polymorphism, whereas the presence of the A allele in some patients was responsible for the required administration of a significantly increased dose of tacrolimus (Tac) that was necessary to reach therapeutic target levels. None of the Tac pharmacokinetic parameters were associated with ABCB1 SNPs, but ABC1 SNPs had early effects on the CsA exposure index and dose requirements. In conclusion, because SNPs of the CYP3A and ABCB1 genes may be associated with CNI pharmacokinetic parameters and exposure indices, pre-transplant genetic screening should be considered in order to avoid immunosuppressant-related adverse events.

Influence of ABCB1 Gene Polymorphisms and P-Glycoprotein Activity on Cyclosporine Pharmacokinetics in Peripheral Blood Mononuclear Cells in Healthy Volunteers

The calcineurin inhibitor cyclosporine is removed from lymphocytes by the drug efflux transporter P-glycoprotein (P-gp) encoded by the ABCB1 gene for which several single nucleotide polymorphisms (SNPs) have been identified. Of a total of 87 healthy volunteers genotyped for ABCB1 G2677T/A and C3435T SNPs, 10 GG-CC and 9 TT-TT individuals were selected and received a single oral dose of cyclosporine. Peripheral blood mononuclear cell (PBMC) ABCB1 mRNA expression, P-gp activity in CD4(+) and CD8(+) cells and the 24h cyclosporine pharmacokinetics in PBMCs and whole blood were determined. No correlation was observed between cyclosporine PBMC and whole blood levels (AUC(0-24), Spearman, r(S)=0.09, p=0.71). Intraindividual PBMC and whole blood levels followed parallel profiles that did not significantly differ with respect to t(max) (Wilcoxon, p=0.53) and t((1/2)) (p=0.49). Significant negative correlations between cyclosporine t((1/2)) in PBMCs and P-gp activity in CD4(+) (r(S)=-0.82, p=0.007) and CD8(+) (r(S)=-0.72, p=0.03) were observed among TT-TT subjects. Similarly, a negative correlation was detected in the GG-CC group between P-gp activity in CD4(+) and cyclosporine PBMC AUC(0-24) (r(S)=-0.69, p=0.03), as well as PBMC to whole blood AUC(0-24) ratio (r(S)=-0.60, p=0.07). Tested ABCB1 genotypes had no influence on cyclosporine pharmacokinetic parameters in PBMCs and whole blood. The haplotypes investigated were neither significantly correlated with PBMC ABCB1 mRNA expression nor with P-gp activity in CD4(+) and CD8(+). In conclusion, cyclosporine PBMC pharmacokinetics was influenced by P-gp activity and cyclosporine whole blood concentrations did not predict PBMC drug levels, suggesting that despite values in the therapeutic range, some subjects could have inadequate intracellular drug levels.

Assessment of Cyclosporine Pharmacokinetic Parameters to Facilitate Conversion From C0 to C2 Monitoring in Heart Transplant Recipients

Background Cyclosporine (CsA) 2-hour postdose (C2) monitoring is recommended to assess CsA exposure and predict clinical outcomes among heart transplant recipients. We correlated pharmacokinetic parameters and clinical outcomes in stable long-term heart transplant recipients monitored with C0 to develop an algorithm to convert patients from C0 to C2 monitoring. Methods Paired CsA C0-C2 measurements and serum creatinine levels were obtained from 35 heart transplant recipients more than 2 years posttransplantation (mean 8.8 ± 4.7 years). Results The mean CsA dose and C0, C2, and C0/C2 ratio were 85 ± 23 mg/12 hours, 123 ± 41 ng/mL, 572 ± 274 ng/mL and 4.8 ± 2.1, respectively. C0 correlated weakly with C2 ( r = .42, P = .011). The CsA dose correlated better with C2 ( r = .58; P < .001) than with C0 ( r = .37; P = .026). A good correlation was noted between C2 and the C2/C0 ratio ( r = .73; P < .001), but none between C0 and the C2/C0 ratio. A borderline significant inverse correlation was noted between C0 and the worst endomyocardial biopsy score ( r = −.34; P = .045), whereas none was noted with C2. Serum creatinine level did not correlate with either C2 or C0. Among patients with C0 within our target of 100 to 150 ug/L, six had C2 above 300 to 600 ug/L as suggested by the literature. Conclusions In long-term heart transplant recipients, we could not identify a single pharmacokinetic parameter that could be used to develop an algorithm to convert from C0 to C2 monitoring; however, C2 may be better than C0 for identifying patients at risk of overexposure to CsA.

Association Between Cyclosporine Concentrations at 2 Hours Post-dose and Clinical Outcomes in De Novo Lung Transplant Recipients

The objective of this study was to investigate the relationship between cyclosporine (CsA) pharmacokinetic parameters and clinical outcomes after lung transplantation. Data from 48 lung or heart/lung transplant recipients originally recruited to a randomized, prospective clinical trial of Sandimmune vs Neoral and followed for 12 months were included in this study. CsA dosing was based on the trough concentration. CsA concentrations at 0 (C0), 2 (C2), and 6 (C6) hours post-dosing were obtained at 1, 2, 3, 4, 13, 26, 39, and 52 post-operative weeks. Based on their average C2 levels in the first post-transplant month, patients were stratified retrospectively into Low C2 (<1,000 microg/liter, n = 18), Intermediate C2 (1,000-1,500 microg/liter, n = 16) and High C2 (>1,500 microg/liter, n = 14) Groups. Cyclosporine C2 was the best single-point determinant (r2 = 0.934) for area-under-the-concentration-time curve (AUC(0-6 hours)) compared with C0 (r2 = 0.267) or C6 (r2 = 0.304). The mean +/- SD values of CsA C2 and AUC(0 to 6 hours) in the first year post-transplant were significantly lower in patients with >2 rejection episodes compared with those with < or =2 rejection episodes (C2: 875 +/- 546 microg/liter vs 1,114 +/- 633 microg/liter, p = 0.01; AUC(0-6 hours): 4,036 +/- 1,904 microg x hour/liter vs 4,870 +/- 2,182 microg x hour/liter; p = 0.01) whereas C0 and C6 did not differ. Patients in the Intermediate C2 Group were free from rejection episodes for a significantly longer duration (p < 0.001) and had significantly higher predicted forced expiratory volume in 1 second (%) values (p < 0.001) compared with the Low and High C2 Groups. The percentage of increase in serum creatinine concentration by the end of first month post-transplant was significantly higher in the Intermediate C2 Group (p < 0.003). CsA C2 concentrations correlated better with the incidence of multiple rejections after lung transplantation than did C0 or C6. C2 concentrations between 1,000 and 1,500 microg/liter within the first post-operative month may be associated with better graft outcomes and improved pulmonary function and worsened renal function.

CYP3A5 and MDR1 genetic polymorphisms and cyclosporine pharmacokinetics after renal transplantation.

The immunosuppressive drug cyclosporine (INN, ciclosporin), whose pharmacokinetic characteristics vary greatly among individuals, is a substrate for cytochrome P450 (CYP) 3A and P-glycoprotein, the product of the multidrug resistance 1 (MDR1) gene. Some of the single nucleotide polymorphisms (SNPs) in these genes are associated with deficient protein expression and reduced in vivo activity. We postulated that, in renal transplant recipients, these SNPs could be associated with interindividual variations in cyclosporine pharmacokinetics. In 106 renal transplant patients, we evaluated retrospectively the effects of 4 MDR1 SNPs [T-129C, C1236T, G2677(T,A), and C3435T] and of the CYP3A5*1/*3 SNP on cyclosporine pharmacokinetic parameters and exposure indices. The CYP3A5*1 allele was present in 8.5% of patients. The MDR1 C1236T, G2677(T,A), and C3435T SNPs were frequent (17.9%, 18.9%, and 33%, respectively, for the variant homozygous genotype) and exhibited incomplete linkage disequilibrium. None of the cyclosporine pharmacokinetic parameters were associated with the CYP3A5 genetic polymorphism. Patients with the wild-type genotype in MDR1 C1236T SNP had slightly but significantly lower dose-adjusted peak drug concentrations (-16%) (P <.02) and dose-adjusted area under the concentration-time curve (AUC) values over the first 4 hours (-14%) (P <.05) as compared with mutated allele carriers. Haplotype analysis including MDR1 C1236T, G2677(T,A), and C3435T SNPs showed no significant association between haplotypes and cyclosporine pharmacokinetics or systemic exposure, although there was a nonsignificant trend toward higher dose-adjusted AUC values over the first 4 hours and AUC over the 12-hour administration interval for the T-T-T haplotype. The presence of the CYP3A5 SNP does not explain the high variability of cyclosporine pharmacokinetics in stable renal transplant patients. Despite the weak association found for the MDR1 C1236T SNP, MDR1 SNPs are unlikely to be useful for cyclosporine dose optimization in clinical practice.

Beneficial pharmacokinetic interaction between cyclosporine and itraconazole in renal transplant recipients

Background Itraconazole is often given for fungal prophylaxis to renal transplant recipients, who require concomitant cyclosporine in the immediate posttransplant period. We determined the extent of the pharmacokinetic interaction between cyclosporine and itraconazole oral solution in renal transplant recipients and the effect on daily drug costs. Method This was a single-center, open-label, nonrandomized study. Posttransplantation, renal transplant recipients received itraconazole solution 200 mg twice daily and cyclosporine, dosed to achieve target concentrations. Once at steady state, blood samples were collected over 12 hours for pharmacokinetic evaluation of cyclosporine, itraconazole, and hydroxy-itraconazole. Itraconazole was discontinued after approximately a 3-month prophylaxis regimen. Cyclosporine doses were titrated to achieve target concentrations and cyclosporine concentrations were once again determined when steady state was achieved. A noncompartmental analysis was used to analyze cyclosporine pharmacokinetic parameters. The pharmacoeconomic impact was measured based on the percent change in dose of cyclosporine when administered with and without itraconazole. Drug costs were calculated using the average wholesale price. The cost per patient, as well as the average cost, was calculated for the cyclosporine/itraconazole combination, as well as the cyclosporine regimen alone. Results Eight renal transplant recipients completed the study. All were included for itraconazole analyses and seven for cyclosporine analyses. Mean peak and trough itraconazole levels were 1.64 ± 0.82 and 1.23 ± 0.90 μg/mL respectively. Mean peak and trough hydroxy-itraconazole levels were 2.37 ± 1.55 and 2.20 ± 1.48 μg/mL, respectively. While on itraconazole, a 48% reduction in the mean total daily dose of cyclosporine was necessary to maintain target concentrations (171 ± 63.6 versus 329 ± 103.5 mg, P = .003). This reduction in cyclosporine dose resulted in a discounted itraconazole daily drug cost of approximately 29.5%. Conclusion Administering itraconazole with cyclosporine allows for a decrease in the cyclosporine dose, thus lowering daily drug costs and providing adequate antifungal coverage with itraconazole and hydroxy-itraconazole trough concentrations above the MIC 90 of Candida and Aspergillus spp.

Ethnic group differences in anger discomfort

The main genes involved in the pharmacokinetics of immunosuppressive drugs are those encoding cytochrome P450 (CYP) family enzymes and multidrug resistance 1 (ABCB1). In this study, 87 Italian teenagers with transplanted kidneys (mean age 11.6 ± 4.8 years) receiving calcineurin inhibitors (CNIs) were genotyped for the single nucleotide polymorphisms (SNPs) CYP3A5*1/3 and CYP3A4*1B for CYP3A, and C1236T, G2677T/A, C3435T and IVS21+49 for ABCB1, and retrospectively evaluated for the influence of the screened SNPs on CNI blood level at different post-transplantation times. The CYP3A5*1 allele was present in 7% of the patients, and the CYP3A4*1B allele was present in 3% of patients. The ABCBl C1236T, G2677T/A and C3435T SNPs C, G and T occurred frequently (55%, 53% and 54%, respectively). The frequency of the T allele of IVS21+49 was 86%. The frequency of SNPs in both genes was comparable with that reported in other European Caucasian populations but different from that found in Asians or Afro-Americans. None of the cyclosporine (CsA) pharmacokinetic parameters were associated with the CYP3A5 genetic polymorphism, whereas the presence of the A allele in some patients was responsible for the required administration of a significantly increased dose of tacrolimus (Tac) that was necessary to reach therapeutic target levels. None of the Tac pharmacokinetic parameters were associated with ABCB1 SNPs, but ABC1 SNPs had early effects on the CsA exposure index and dose requirements. In conclusion, because SNPs of the CYP3A and ABCB1 genes may be associated with CNI pharmacokinetic parameters and exposure indices, pre-transplant genetic screening should be considered in order to avoid immunosuppressant-related adverse events.

C3435T mutation in exon 26 of the human MDR1 gene and cyclosporine pharmacokinetics in healthy subjects.

To determine the relationship between C3435T mutation in exon 26 of the human multidrug resistant 1 (MDR1) gene and cyclosporine pharmacokinetic parameters among healthy volunteers, the oral cyclosporine pharmacokinetic study was performed for 14 healthy subjects. Blood cyclosporine concentrations were measured by HPLC. Concentration-time data were analyzed by a noncompartmental method using WinNonLin, and the blood samples were genotyped for the C3435T polymorphism of MDR1 gene using the PCR and a restriction digest. Each cyclosporine pharmacokinetic parameter was compared using the Mann-Whitney U test according to his or her P-gp genotype. There were seven (7) homozygous C/C, six (6) C/T, and one (1) homozygous T/T genotypes in these 14 healthy volunteers. According to their genotypes, mean t(max) 1.6 +/- 0.3 hours, mean C(max) 1337 +/- 329 ng/mL, mean Cl/F 66.5 +/- 18.3 L/h, and mean AUC 5642 +/- 1577 ng.h/mL in C/C group and mean t(max) 2.0 +/- 0.6 hours, mean C(max) 1540 +/- 721 ng/mL, mean Cl/F 55.2 +/- 18.9 L/h, and mean AUC 6902 +/- 1405 ng.h/mL in C/T+T/T group. Although Cmax and AUC in C/T and T/T group were 15% and 22% larger than those in C/C group, none of these parameter comparisons was statistically significant. There were no statistical differences in cyclosporine pharmacokinetics among different MDR1 genotypes in these 14 healthy subjects.

Evaluation of The Pharmacokinetic Interaction Between Cemetidine or Famotidine and Cyclosporine in Healthy Men

To investigate the potential interaction between cimetidine or famotidine and cyclosporine in healthy men. All subjects received oral cyclosporine at baseline, after the first week of 1 histamine2 (H2)-blocker, and a third time after a 1-week washout plus 1 week of the second H2-blocker. Blood samples were collected just before each dose of cyclosporine and for up to 36 hours afterward for pharmacokinetic analysis. A college of pharmacy in a university teaching hospital. The study population consisted of 8 healthy men at least 19 years of age. Cyclosporine concentrations in whole blood were measured using a polyclonal fluorescence polarization immunoassay. Cyclosporine pharmacokinetic parameters during each of the 3 treatment periods were compared. The average times to maximum cyclosporine concentrations were similar between baseline (3.2 h), cimetidine (2.9 h), and famotidine (3.6 h) dosing periods. There were no significant differences in area under the curve, half-life, or maximum concentration during the 3 dosing periods. Neither cimetidine or famotidine produced a significant change in the pharmacokinetics of single-dose oral cyclosporine in healthy men.

The adverse impact of high cyclosporine. Clearance rates on the incidences of acute rejection and graft loss.

The influence of cyclosporine pharmacokinetic parameters on clinical events and outcome after transplantation was studied in 100 renal transplant recipients who underwent a pre- as well as posttransplant CsA pharmacokinetic evaluation. Among the patients, 30 were black and 50 were white. Black recipients had significantly lower bioavailability (F) pre- as well as posttransplantation than white recipients, the posttransplant mean F values being 25.8 +/- 9.0% and 38.1 +/- 16.7%, respectively (P < 0.002). The posttransplant CsA clearance rate (CL) and oral clearance (clearance/bioavailability; CLoral) were significantly higher in patients who had acute rejection than in those who did not, with CL mean values of 425 +/- 141 ml/min and 359 +/- 131 ml/min, respectively (P < 0.02). The initial posttransplant F was significantly lower, and the CLoral higher in patients who eventually lost their grafts than in those who did not, the mean F values being 26.5 +/- 12.8% and 38.7 +/- 17.5%, respectively (P < 0.002). Thus, several important relationships between CsA pharmacokinetic parameters and clinical events following renal transplantation were documented. The CLoral decreased during the first 3 months after transplantation (P < 0.0001), but it was stable thereafter. Neither the bioavailability nor the clearance of CsA showed a correlation with administered dose. These results indicate that certain recipient groups, such as black patients, and individuals with rapid CL, may benefit from larger CsA doses and/or shorter dosage intervals, in order to compensate for these interpatient variabilities.

Cyclosporine (cyclosporin A) pharmacokinetics in renal transplant patients receiving ciprofloxacin

The effects of ciprofloxacin administration on the pharmacokinetic parameters and biologic tolerance of cyclosporine (cyclosporin A) were determined in primary renal transplant patients. This study was performed in 10 patients (four women and six men) ranging in age from 26 to 64 years and body weight ranging from 46 to 88 kg. Ciprofloxacin therapy was started eight to 48 days (mean, 21 days) after transplantation, whereas the cyclosporine therapy was administered for seven to 48 days (mean, 18 days) post-transplant. Both ciprofloxacin and cyclosporine were administered every 12 hours. The mean cyclosporine dosage was 2.4 mg/kg per day, adjusted to obtain blood concentrations within the recommended range (i.e., 100 to 200 ng/ml). The ciprofloxacin dosage was 750 mg orally twice daily for all patients. A pharmacokinetic study of cyclosporine was performed in each patients the day before starting ciprofloxacin treatment and after the 13th ciprofloxacin administration (i.e., Day 7 of ciprofloxacin therapy). Cyclosporine concentrations were measured in whole blood by a specific high-performance liquid chromatography method and the following parameters were determined: minimal and maximal blood concentrations, area under the curve from zero to 12 hours, total body oral clearance, mean residence time, and elimination half life. Concurrently administered medications and serum creatinine values were recorded. No statistically significant difference was noted between the cyclosporine pharmacokinetic parameters before and during ciprofloxacin treatment. Serum creatinine levels were increased in four of 10 patients, but the increase was not considered related to ciprofloxacin treatment. In conclusion, it appears that ciprofloxacin can be administered to renal transplant patients without risk of interacting cyclosporine or enhancement of cyclosporine nephrotoxicity. Additional cyclosporine blood level monitoring is not particularly valuable in this setting.

Analytical Methodologies for Cyclosporine Pharmacokinetics: A Comparison of Radioimmunoassay with High Performance Liquid Chromatography

Abstract Radioimmunoassay (RIA) and high performance liquid chromatography (HPLC) with ultraviolet absorbance detection have been compared as potential analytical methods for cyclosporine pharmacokinetic studies. Cyclosporine concentrations were measured by each method in the serum and bile of cyclosporine—treated humans and in the plasma and urine of cyclosporine—treated dogs. While clearly affording greater assay sensitivity, RIA overestimates concentrations of parent cyclosporine, ostensibly because of cross—reactivity with cyclosporine metabolites. Thus, RIA—measured time course data result in underestimations of primary pharmacokinetic parameters, volume of distribution and clearance. Ratios of measured concentrations (RIA/HPLC) in human bile are significantly greater than those in serum, lending further evidence to the previously—suggested metabolite interference with RIA. Similar results were obtained from the urine of cyclosporine—treated dogs. Moreover, ratios (RIA/HPLC) in dog plasma rise and then decline as a function of post—administration time, reaching a peak in approximately 8 hours. This might be consistent with the formation and disposition of metabolites. HPLC appears to be specific for parent cyclosporine. Thus, HPLC—measured time—course data afford more reliable estimates of cyclosporine pharmacokinetic parameters, although for certain studies, sensitivity might be less than adequate.

CYCLOSPORINE DISPOSITION IN THE DOG

Radioimmunoassay (RIA) and high performance liquid chromatography (HPLC) with ultraviolet absorbance detection have been compared as potential tools for cyclosporine pharmacokinetic studies in dogs. RIA clearly affords greater assay sensitivity, although crossreactivity with cyclosporine metabolites causes an over-estimation of parent drug concentrations with a subsequent reduction in the apparent values of clearance and volume of distribution. HPLC appears to be specific for parent cyclosporine. Thus, with the sacrifice of some sensitivity, HPLC-measured time-course data afford more reliable estimates of cyclosporine pharmacokinetic parameters. After the selection of a dosage regimen from preliminary studies, the pharmacokinetics of i.v.-administered cyclosporine were studied in six adult male mongrel dogs. Following administration of 20 mg/kg by constant-rate 30-min i.v. infusion the time courses of cyclosporine were studied in plasma and urine. Concentrations were measured by reversed-phase HPLC with ultraviolet absorbance detection. Data were fitted to triexponential equations using a digital computer with the CSTRIP and NONLIN programs, and pharmacokinetic parameters were calculated. Present findings suggest that cyclosporine is slowly yet extensively distributed into peripheral body regions that might serve as slowly releasing storage areas. Large volumes of distribution along with moderately slow clearances resulted in long half-lives for the disposition of cyclosporine. Less than 1% of the administered dose was recovered as parent cyclosporine in the urine, suggesting that renal clearance of cyclosporine was negligible. The potential relevance of present findings to cyclosporine therapy of transplant patients is discussed.