Renal Transplantation

Polymorphisms in the CYP3A5 gene significantly affect the pharmacokinetics of sirolimus after kidney transplantation

Aim: Sirolimus (SIR) is an immunosuppressant with limitations, including a narrow treatment window, multiple adverse reactions and large differences within and among individuals. Objective: The correlation between numerous SNPs and SIR in terms of trough concentration in the early stage after kidney transplantation was analyzed. Materials & methods: A retrospective cohort study involving 69 kidney transplantation recipients was designed. Blood samples were collected to extract total DNAs, and trough SIR concentrations were measured. Logistic regression was used to analyze the association between SNPs and SIR trough concentrations. Results: At 7 days, 1 month and 3 months, the mean SIR trough concentration of patients in the CYP3A5 rs4646453-CC group was significantly higher than that in the CYP3A5 rs4646453-AA and CYP3A5 rs4646453-CA groups (p < 0.001) and CYP3A5 rs15524-AA group was significantly higher than that in the CYP3A5 rs15524-AG and CYP3A5 rs15524-GG groups (p < 0.001). Conclusion: Our study indicated that both CYP3A5 rs4646453 and CYP3A5 rs15524 had a certain influence on SIR trough concentration at 7 days, 1 month and 3 months.

Training protocol for feline renal transplantation, using rat vascular anastomosis

Renal transplantation (RTx) has been a potential treatment for renal failure in pet cats. We developed a training protocol for the microsurgical skills required for feline RTx using rat vessels, which are the same size as the feline renal artery and vein. Using interrupted sutures, the transected abdominal aorta was reestablished in an end-to-end fashion. Venous anastomosis was performed with a continuous running suture in an end-to-side fashion between the portal vein and inferior vena cava. In the arterial anastomotic model, technical errors were checked by postoperative hemorrhaging. Those failures in the venous anastomotic model, technical errors were confirmed by the rat's death. Histological examinations of the epithelialization at the anastomotic site were evaluated in both groups. After training, nine cases of feline RTx were performed safely, using an adequate microsurgical technique.

Use of nonpenetrating vascular closure staples in feline renal transplantation

Renal transplantation is a potential treatment for irreversible renal failure in pet cats. Our aim is to reduce warm ischemic time by using nonpenetrating vascular closure staples (VCS), thereby improving graft survival. Experimental cats were divided into the VCS group (n = 4; autotransplantation) or suture group (n = 6; allotransplantation). The renal artery was anastomosed with the external iliac artery in an end-to-end fashion, and the renal vein was attached to the external iliac vein in an end-to-side fashion. Warm ischemic time as well as arterial and venous anastomotic times were measured. Cats in the suture group were administrated cyclosporine and prednisolone orally after transplantation. Ischemic and anastomotic times in the VCS group were significantly reduced compared with the suture group. Two of 6 allografts had a ureteral anastomotic stricture, and 4 allografts were rejected. Histological findings of autografts showed normal structure. In conclusion, VCS staples were useful in feline renal transplantation.

Screening criteria for feline renal transplant recipients and donors

Renal transplantation is associated with several potential complications. Early selection and appropriate screening of candidates has reduced the morbidity and mortality associated with this procedure in human beings. In veterinary medicine, the important process of identification and screening of candidates for renal transplantation occurs primarily in private general or specialty practice. This article reviews guidelines for screening of candidates for renal transplantation and related publications in both veterinary and human literature in an attempt to provide comprehensive information to practitioners involved in the selection process. It is anticipated that early referral of stable cats for renal transplantation will further improve the likelihood of a successful outcome.

Diagnostic predictors of complications and survival after renal transplantation in cats

OBJECTIVE

To identify preoperative diagnostic results that predict postoperative complications and survival in feline renal-transplant recipients.

STUDY DESIGN

Retrospective clinical study.

ANIMALS

Sixty-one feline renal allograft recipients.

METHODS

Medical records for 61 consecutive cats that underwent renal allograft transplantation between January 1, 1996, and December 1, 1999, were reviewed. Age, diagnosis, body weight, body condition score, preoperative medical treatment, systolic blood pressure, packed cell volume, biochemical parameters at admission and at the time of surgery, postoperative complications, and postoperative survival were recorded. Associations of preoperative data with the occurrence of postoperative complications were determined using logistic regression. Postoperative survival was graphed using a Kaplan-Meier cumulative-survival plot. Associations of covariates with postoperative survival were analyzed using Cox proportional hazards analysis.

RESULTS

Two parameters were significantly associated with occurrence of postoperative central nervous system (CNS) disorders: blood urea nitrogen concentration (odds ratio = 1.083; 95% CI = 1.018 to 1.148) and serum creatinine concentration (odds ratio = 1.8; 95% CI = 1.413 to 2.187) at the time of surgery. Postoperative survival 6 months after transplantation was 59%, though 3-year survival remained at 42%. Of all covariates investigated, only recipient age (relative hazard = 1.183; 95% CI = 1.039 to 1.334) was significantly associated with survival.

CONCLUSION AND CLINICAL RELEVANCE

Standard measures of preoperative renal dysfunction do not predict postoperative survival in cats after renal transplantation, although an increase in the degree of preoperative azotemia is associated with an increased risk of CNS disorders after surgery. Increased recipient age is associated with decreased survival after renal transplantation.

Low intraindividual variability of cyclosporin A exposure reduces chronic rejection incidence and health care costs

The present study applied a receiver operating characteristic (ROC) analysis to assess the role of intraindividual variability of cyclosporin A (CsA) drug exposure in predisposing renal transplant recipients to the occurrence of chronic rejection, as well as to increased health care costs using a resource-based economic analysis. Two hundred and four adult renal transplant recipients were treated with tapering doses of prednisone (Pred) and with a concentration-controlled strategy that selected doses of the olive oil-based formulations of CsA (Sandimmune(R)) that achieved target concentrations based on serial pharmacokinetic profiles. The ROC analysis revealed an inflection point of plots of the coefficient of variation (%CV) of CsA exposure versus the risk of chronic rejection at >/=28.4% for the average concentration (C(av)), i.e., the dosing interval-corrected area under the concentration-time curves, and >/=36% for the trough concentration (C(0)). The incidence of chronic rejection over a period of 5 yr was 24% among the less variable (LV) versus 40% among the variable (V) cohort. The economic analysis revealed that the total mean facility and physician costs per patient were $48,789 versus $60,998, respectively (P < 0.01). The degree of variability displayed by any individual could only be predicted by serial measurements of CsA concentrations, and not by demographic features, laboratory determinations, clinical characteristics, individual or mean values of any observed CsA concentration, or other pharmacokinetic parameters calculated following a single drug exposure. Thus, strategies that reduce intrapatient variability of CsA exposure over time may lead to reductions in chronic allograft loss and in treatment costs.

Sirolimus-induced thrombocytopenia and leukopenia in renal transplant recipients: risk factors, incidence, progression, and management

BACKGROUND

Our study assessed the factors that predispose renal transplant recipients to the occurrence of thrombocytopenia and leukopenia, as well as the severity and the time- and concentration-dependence of these side-effects, after administration of sirolimus (SRL) in combination with a cyclosporine (CsA) and prednisone (Pred) regimen.

METHODS

The clinical courses of two cohorts of renal transplant recipients were compared over 1 year: 119 patients received SRL in addition to CsA and Pred, and 65 demographically similar, concurrent patients received only CsA and Pred. Using an analysis of variance, pretransplant laboratory values and SRL trough concentrations (C0) were correlated with the occurrence, severity, and persistence of drug-induced thrombocytopenia (platelet count <150x10(3) cell/mm3) and/or leukopenia (white blood cell count <5,000/mm3).

RESULTS

Neither the ethnic background nor the pretransplant cytomegalovirus serological status was associated with the occurrence of hematological complications. Thrombocytopenia was usually observed during the first 4 weeks of treatment (P=0.004). The occurrence, but not the severity or the persistence, of both thrombocytopenia and leukopenia correlated significantly with SRL trough concentrations > or =16 ng/ml (P=0.001 and 0.0001, respectively). A significant correlation is evident between the occurrence of the two adverse effects (P=0.001). In 89% of patients, the first episode of either type of cytopenia resolved spontaneously. Among the remaining 11%, 7% responded to SRL dose reduction, and 4% to temporary suspension. No patient required permanent cessation of SRL therapy. Most patients experienced repeated, but self-limited, episodes of toxicity.

CONCLUSION

Thrombocytopenia and leukopenia are not infrequent occurrences with SRL treatment, and they generally resolve spontaneously.

Conversion from liquid to solid rapamycin formulations in stable renal allograft transplant recipients

Sirolimus (rapamycin, RAPA, Rapamunetrade mark) is a potent immunosuppressive agent currently being investigated for prophylaxis against acute rejection episodes in renal transplant recipients. In the present study, stable renal allograft recipients under maintenance therapy with RAPA and cyclosporine (CsA) were converted from the original oil-based liquid RAPA to a solid tablet formulation on a milligram-to-milligram basis, in order to evaluate the pharmacokinetics and safety of this new dosage form. Twelve-hour pharmacokinetic (PK) profiles of both RAPA and CsA were conducted with the final liquid RAPA dose, and at 2, 4, and 8 weeks postconversion to the solid tablet. In addition, the parameters of the PK profiles for the solid formulation were compared with those for liquid RAPA, which were performed prior to this study. Area under the concentration-time curve (AUC) values for the liquid formulation and for the solid tablet at 2, 4, and 8 weeks postconversion were 256.5, 205.8, 226.1, and 224.4 ng.h/mL, respectively (p=NS). Time to maximum RAPA concentration was longer at 4 weeks postconversion, but similar at 2 and 8 weeks. There were no differences observed between the liquid and solid tablet trough concentrations. The only significant differences observed among the PK parameters of the solid tablet versus those of the liquid formulation were the lower C(max) values of the solid, namely 25.3, 24.9, and 26.7 ng/mL versus 37.1 ng/mL (p<0.05). In addition, the dose corrected C(max) was lower in the solid tablet PK profiles compared with the prior PK profiles for the liquid (7.7 versus 10.2 ng/mL, p<0.02). Cyclosporine AUC values did not change appreciably during the study. Conversion from the liquid to the solid formulation was neither associated with episodes of acute rejection, nor changes in laboratory values, during the 8-week study. In summary, conversion from the liquid to the solid RAPA formulation resulted in similar PK profiles and appears to be both safe and well-tolerated in renal transplant recipients.

Local graft irradiation after failure of modern immunosuppression in acute cellular and vascular graft rejection

PURPOSE

With improved chemical immunosuppressive agents, approximately 90% of rejection episodes can be reversed. However, in situations of failed immunosuppression, graft loss becomes inevitable. Our objective is to assess the efficacy of local graft irradiation (LGI) as an effort of last resort in a contemporary group of patients in whom graft failure to irreversible cellular and vascular rejection is imminent.

METHODS AND MATERIALS

A total of 308 renal transplantations were performed at our institution from 1992 to 1995, and an overall 1-year graft survival rate of 90% has been seen as a result of improvement in chemical immunosuppression. However, 6 patients were referred for LGI when all other measures failed to reverse the rejection crisis. Parameters that were studied in these patients included graft function and postirradiation graft histology.

RESULTS

Irradiation was associated with reversal of the rejection crisis and resulted in documented histological long-term graft survival in 1 of the 6 patients (17%). Two of the six patients (33%) had reversal of the rejection episode based on postirradiation biopsy of the renal allograft. Three of the six patients showed some level of clinical improvement of graft function for varying periods of time. One patient maintained stable allograft function without deterioration and with continued independence from hemodialysis. One recipient died from sepsis despite histologic improvement after irradiation.

CONCLUSIONS

Our impression is that LGI is indicated when all other measures have failed to reverse an acute rejection episode in the transplanted renal allograft. The role of radiation in this setting should be studied further.