Reduced kidney transplant rejection rate and pharmacoeconomic advantage of mycophenolate mofetil

Prevalence of mycophenolate mofetil discontinuation and subsequent outcomes in pediatric kidney transplant recipients: A PNRC study

BACKGROUND

Mycophenolate Mofetil (MMF) is an effective immunosuppressant used in kidney transplant recipients to prevent acute rejection. Complications such as diarrhea, leukopenia, and infections may necessitate the reduction or discontinuation of MMF. The objective of the study was to investigate the prevalence, timing, and reasons for MMF discontinuation and its association with outcomes in pediatric kidney transplant recipients.

METHODS

Seven Pediatric Nephrology Research Consortium (PNRC) centers participated in a retrospective analysis of kidney transplant recipients <21 years of age. Characteristics and outcomes of patients in whom MMF was discontinued were compared to those who continued taking MMF throughout the first 2 years post-transplant.

RESULTS

The study population included 288 participants (mean age 11.2 years) from 7 North American transplant centers. MMF was discontinued in 93/288 (32%) of participants. Common reasons for discontinuation included infections (35%), diarrhea (32%), leukopenia (15%), and others (18%). Increased cumulative alloimmunity (55% vs. 42%, p = .02), increased number of hospitalizations (82% vs. 67%, p = .01), and viral replications (79% vs. 47%, p < .0001) were observed in the MMF discontinuation group compared to the continuation group. Greater eGFR decline also occurred in the MMF discontinuation group over 2 years of follow-up (-7 vs. -1 mL/min/1.73 m2 , p = .05).

CONCLUSIONS

Almost a third of pediatric kidney transplant recipients who begin MMF for maintenance immunosuppression have it discontinued within the first 2 years post-transplant, and this subset of patients is more likely to experience adverse outcomes. New strategies are needed to manage MMF therapy and improve post-transplant outcomes.

Chronic Renal Transplant Rejection and Possible Anti-Proliferative Drug Targets

The global prevalence of renal transplants is increasing with time, and renal transplantation is the only definite treatment for end-stage renal disease. We have limited the acute and late acute rejection of kidney allografts, but the long-term survival of renal tissues still remains a difficult and unanswered question as most of the renal transplants undergo failure within a decade of their transplantation. Among various histopathological changes that signify chronic allograft nephropathy (CAN), tubular atrophy, fibrous thickening of the arteries, fibrosis of the kidney interstitium, and glomerulosclerosis are the most important. Moreover, these structural changes are followed by a decline in the kidney function as well. The underlying mechanism that triggers the long-term rejection of renal transplants involves both humoral and cell-mediated immunity. T cells, with their related cytokines, cause tissue damage. In addition, CD 20+ B cells and their antibodies play an important role in the long-term graft rejection. Other risk factors that predispose a recipient to long-term graft rejection include HLA-mismatching, acute episodes of graft rejection, mismatch in donor-recipient age, and smoking. The purpose of this review article is the analyze current literature and find different anti-proliferative agents that can suppress the immune system and can thus contribute to the long-term survival of renal transplants. The findings of this review paper can be helpful in understanding the long-term survival of renal transplants and various ways to improve it.

Comparison of MMF with prednisone in terms of rejection and duration of activity of transplant in rabbits that underwent retroperitoneal heterotopic heart transplantation

AIM

In this study, mycophenolate mofetil (MMF) and methylprednisolone (MP) were compared in terms of rejection and duration of activity of the transplant in New Zealand rabbits that underwent retroperitoneal heart transplantation.

METHODS

Retroperitoneal heart transplantation was performed in New Zealand white rabbits. The animals were divided into two groups. MMF group (group 1) (10 donors, 10 recipients): 12.5 mg/kg MMF was administered orally for two days prior to the surgery; MP group (group 2) (nine donors, nine recipients): 2 mg/kg MP was administered intramuscularly for two days prior to the surgery. After the operation, we waited until all motor activity in the transplanted heart had stopped. The transplant was then removed and the recipient was sacrificed. A donor in the MP group was excluded since it died before the motor activity had stopped.

RESULTS

No statistically significant difference was found between the groups in terms of rejection score (p = 0.865). However, duration of motor activity was found to be statistically significantly longer in the MMF group, compared to the MP group (p = 0.013).

CONCLUSION

In this experimental study, MMF was similar to MP in terms of rejection but had better efficacy in terms of duration of motor activity of the transplant.

Acute colonic pseudo-obstruction caused by mycophenolate mofetil in a kidney transplant recipient

Mycophenolate mofetil is a component of immunosuppressive regimens in solid-organ transplant recipients. Gastrointestinal symptoms such as nausea, abdominal pain, and diarrhea without fever are common in patients treated with mycophenolate mofetil. We treated a patient who had acute colonic pseudo-obstruction after kidney transplant that resolved after discontinuing mycophenolate mofetil. The disorder recurred soon after resuming mycophenolate mofetil, which is evidence for an association between mycophenolate mofetil and acute colonic pseudo-obstruction in this patient.

Nierentransplantation

Die Nierentransplantation ist die effektivste Behandlungsmethode der chronischen terminalen Niereninsuffizienz. Seit den 1960er Jahren entwickelte sie sich zu einer Standardtherapie. Wichtige Voraussetzungen waren die Entdeckung des HLASystems, die Entwicklung der Immunsuppressiva sowie die technische Perfektionierung des Organerhaltes außerhalb eines lebenden Körpers. Die 5- Jahres-Überlebensrate für Allotransplantate beträgt etwa 65%, diejenige von Lebendspenden 79%. Die Einrichtung von zentralen Erfassungsstellen, wie z. B. Eurotransplant (Deutschland, Benelux- Staaten, Österreich, Slowenien), ist für die Organisation des zeitgebundenen Ablaufes von großer Bedeutung. Bei diesen Institutionen sind alle potentiellen Nierenempfänger registriert. Dort werden auch alle potentiellen Spenderorgane gemeldet und dem passenden Empfänger zugeordnet.

Mycophenolate mofetil: ten years' experience of a renal transplant unit

Mycophenolate mofetil (MMF) use in renal transplantation has allowed a significant decrease in early acute rejection rates. We retrospectively evaluated the incidence of acute rejection episodes, renal function at the first year posttransplant, patient and graft survivals, cytomegalovirus (CMV) infection rate, influence of the degree of sensitization, and number of MHC antigen mismatches on graft survival in two groups of patients receiving either MMF or azathioprine. Group 1 included 149 patients receiving cyclosporine, MMF, and prednisolone; group 2 included 191 patients receiving cyclosporine, azathioprine, and prednisolone. The two groups did not differ in terms of age, sex, degree of sensitization (expressed as percentage of antibodies reactive to panel), MHC mismatch number, cold ischemia time, donor age, or anti-thymocyte globulin induction. In group 1 (MMF) there was a significant decrease in early acute rejection rate (19% vs 57%, P < .0001), longer graft survival at 10 years (92% vs 75%, P = .006), and higher rate of CMV infection (22% vs 12%, P = .004). Renal function at the first year posttransplant and patient survival during follow-up did not differ between the groups. The degree of sensitization influenced graft survival in group 2. The number of MHC mismatches did not influence graft survival in either group. With MMF, there was a significant reduction in early acute rejection rate, a significant increase in graft survival at 10-year follow-up, and diminished impact of the degree of sensitization on graft survival.

Changing treatment protocol from azathioprine to mycophenolate mofetil: decrease in renal dysfunction, increase in infections

INTRODUCTION

Immunosuppression for renal transplantation has shifted from azathioprine (AZA) regimens to those containing mycophenolate mofetil (MMF). This study investigated the impact of this change on the causes for rehospitalization as well as on graft and patient survival.

METHODS

In this retrospective cohort study, we reviewed long-term patient and graft survivals as well as the causes of posttransplant admissions for 893 kidney recipients. Data on survival and readmissions were available for 811 subjects, who were divided to into the AZA cohort (n=289, transplantation between 1998 and 1999) and the MMF cohort (n=567, transplantation between 2000 and 2001). Survival, the cause for readmission, time interval between transplantation and readmission, intensive care unit (ICU) admission, mortality, and graft loss were compared between the two cohorts.

RESULTS

Five-year patient and graft survival rates were 85% and 67% for the AZA cohort and 91% and 68% for the MMF cohort (P=.013). There were 202 (71%) and 371 (72%) readmissions registered for the AZA and MMF groups, respectively. In comparison with the AZA cohort, while readmissions secondary to graft rejection showed a significant decrease in the MMF cohort (62% vs 35%, P=.000), readmissions secondary to infections exhibited a significant increase (37% vs 50%, P=.002). A marginally significant increased mortality rate (2% vs 5%, P=.087) and ICU admission rate (3% vs 6%, P=.062) were also observed in the MMF cohort by comparison with the AZA cohort.

CONCLUSION

The shift in the immunosuppression protocol from AZA to MMF, albeit advantageous in many instances, can sometimes undermine the outcome by giving rise to such complications as high infection rates.

Update on Pharmacoeconomics in Transplantation

Purpose

To provide current information on pharmacoeconomic outcomes in transplantation for the past 6 years.

Methods

An extensive literature search was undertaken using PubMed and other authenticated Internet sources. Key words used to elicit pertinent studies were “pharmacoeconomics,” “transplantation,” “cost-effectiveness,” “cost-benefit,” “cost-minimization” and “cost-utility” analyses. Studies included in the review contain updated pharmacoeconomic data generated during the past 6 years on economic, clinical, and humanistic outcomes. These data are used to describe and analyze the cost of drug therapy used in transplantation.

Results

Background information is included in the review to provide a context from which to evaluate new study material. Data extracted from the studies include significant findings and study limitations. Data were stratified into understanding pharmacoeconomic methods and their application to transplantation, maintenance and induction therapies, and management of and costs associated with adverse events and quality-of-life issues.

Conclusions

Continued evolution of pharmacoeconomic analysis is needed so that optimal care can be provided in the most cost-effective manner. Pharmacoeconomic study, done rationally and logically, is an indispensable tool in determining optimal transplantation regimens.

Hospitalization Databases: A Tool for Transplantation Monitoring

INTRODUCTION

We sought to account for changes in posttransplant hospitalization patterns in terms of the changes in demographic and transplantation-related variables.

METHODS AND MATERIALS

We retrospectively analyzed 1860 cases of kidney transplantation performed between 1992 and 2004 in terms of demographic and transplantation-related variables. Of the 1860 cases, rehospitalization records in the first year posttransplantation were available for 1152 cases, which were assessed for causes of admission, mortality, graft loss, length of stay, and hospital charges.

RESULTS

The pattern of rehospitalizations showed the following trends: (1) Increased rate of infection; (2) Decreased rate of graft rejection; and (3) Peak costs of rehospitalization between 1999 and 2000.

CONCLUSION

We believed that the increased infection rate and decreased rejection rate may have been related at least partly to the shift in the treatment protocol from azathioprine-based to mycophenolate mofetil regimens in 2000. Furthermore, the peak in the relative frequency of diabetes mellitus and hypertension as the etiology of end-stage renal disease among those having undergone transplantation between 1999 and 2000 may have been responsible for the peak in rehospitalization costs and length of hospital stay. We are strongly of the opinion that hospital statistics are a valuable tool for health care policymakers to monitor transplantation outcomes.

Nierentransplantation

Die Nierentransplantation ist die effektivste Behandlungsmethode der chronischen terminalen Niereninsuffizienz. Seit den 1960er Jahren entwickelte sie sich zu einer Standardtherapie. Wichtige Voraussetzungen waren die Entdeckung des HLA-Systems, die Entwicklung der Immunsuppressiva sowie die technische Perfektionierung des Organerhaltes außerhalb eines lebenden Körpers. Die 5-Jahres-Überlebensrate für Allotransplantate beträgt etwa 65%, diejenige von Lebendspenden 79%.

Effects of mycophenolate mofetil on donor-specific antibody formation in renal transplantation

BACKGROUND

Mycophenolate mofetil (MMF) is a routinely used immunosuppressive agent that selectively blocks T- and B-lymphocyte proliferation. The present study was designed to investigate the effects of this drug on human leukocyte(HLA) antibody production in general and donor-specific antibody (DSA) formation in particular in 154 recipients of renal allografts.

PATIENTS AND METHODS

Renal allograft recipients were subdivided into three groups. Group 1 patients (n = 60) had received MMF since transplantation in combination with either cyclosporin A or tacrolimus and steroids. Group 2 patients (n = 29) had received an MMF-free immunosuppressive regimen initially followed by addition of MMF some time later. Group 3 patients (n = 65) had received no MMF. Cyclosporin A or tacrolimus in combination with azathioprine and/or steroids were used for immunosuppression. DSA were demonstrated by enzyme-linked immunosorbent assay (ELISA) for detection of panel-reactive antibodies of HLA class I and II specificity.

RESULTS

The HLA antibodies were found in 16.7%, 27.6% and 30.8% of transplant recipients in groups 1, 2 and 3, respectively. DSA were found in 8.3%, 17.2% and 20.0%, and non-DSA in 10.0%, 20.7% and 24.6%, of patients in groups 1, 2 and 3, respectively.

CONCLUSION

The MMF reduces anti-HLA class I and II antibody production and consequently DSA production in renal allograft recipients. Our data indicate this effect to be more pronounced in patients given MMF immediately after transplantation than in those in whom MMF is introduced some time later. The presence of DSA in the serum of renal allograft recipients is associated with poorer graft function (higher serum creatinine and more rejection episodes).

Improvement in long-term graft survival in cadaveric renal transplant recipients treated with mycophenolate mofetil

Though mycophenolate mofetil has markedly reduced the incidence of acute rejection in renal transplantation, a significant improvement in graft survival has been more difficult to demonstrate. This retrospective study compares an historical control group of 210 consecutive renal transplant patients, who had received ATG induction associated with cyclosporin, prednisolone and azathioprine, with 187 patients receiving mycophenolate instead of azathioprine. The incidence of acute rejection was decreased with mycophenolate. In rejection-free patients, the 3-year graft survival rates were equivalent. In contrast, graft survival at 3 years improved significantly for patients who experienced a rejection crisis and remained under the initial triple drug regimen with mycophenolate compared to the patients of the historical group who were kept on azathioprine after a rejection episode. In conclusion, mycophenolate mofetil is not only able to reduce the incidence of acute rejection but could also improve the prognostic significance of acute rejection crises.

Pediatric renal transplantation with mycophenolate mofetil-based immunosuppression without induction: results after three years

BACKGROUND

Mycophenolate mofetil (MMF)-based immunosuppression has reduced the acute rejection rate in adults and in children in the early posttransplantation period. Three-year posttransplantation results have been reported for adults but not for children thus far. In the present open-labeled study, patients 18 years old and younger were evaluated prospectively for up to 3 years after renal transplantation (RTX).

METHODS

Eighty-six patients receiving MMF in combination with cyclosporine and prednisone without induction were evaluated for patient survival, transplant survival, renal function, arterial blood pressure, adverse events, and opportunistic infections. These patients were compared with a historic control group (n=54) receiving azathioprine (AZA) instead of MMF.

RESULTS

Patient survival after 3 years was 98.8% in the MMF group and 94.4% in the AZA group (NS). Intent-to-treat analysis of graft survival demonstrated superiority for MMF (98% vs. 80%; P<0.001). Cumulative acute rejection episodes occurred in 47% of patients in the MMF group versus 61% in the AZA group (P<0.05). Renal function was not significantly different, neither after 3 years nor in the long-term calculation. Antihypertensive medication was administered to 73% to 84% of patients, similar in both groups. Opportunistic infections were recorded only for MMF. Infection rates were comparable to those reported in adults.

CONCLUSIONS

These results suggest that MMF is safe and beneficial as a longer term maintenance immunosuppressive drug in children and adolescents.

Dialysis, kidney transplantation, or pancreas transplantation for patients with diabetes mellitus and renal failure: a decision analysis of treatment options

Patients with type 1 diabetes mellitus and end-stage renal disease may remain on dialysis or undergo cadaveric kidney transplantation, living kidney transplantation, sequential pancreas after living kidney transplantation, or simultaneous pancreas-kidney transplantation. It is unclear which of these options is most effective. The objective of this study was to determine the optimal treatment strategy for type 1 diabetic patients with renal failure using a decision analytic Markov model. Input data were obtained from the published medical literature, the United Network for Organ Sharing registry, and patient interviews. The outcome measures were life expectancy (in life-years [LY]) and quality-adjusted life expectancy (in quality-adjusted life-years [QALY]). Living kidney transplantation was associated with 18.30 LY and 10.29 QALY; pancreas after kidney transplantation, 17.21 LY and 10.00 QALY; simultaneous pancreas-kidney transplantation, 15.74 LY and 9.09 QALY; cadaveric kidney transplantation, 11.44 LY and 6.53 QALY; dialysis, 7.82 LY and 4.52 QALY. The results were sensitive to the value of several key variables. Simultaneous pancreas-kidney transplantation had the greatest life expectancy and quality-adjusted life expectancy when living kidney transplantation was excluded from the analysis. These data indicate that living kidney transplantation is associated with the greatest life expectancy and quality-adjusted life expectancy for type 1 diabetic patients with renal failure. Treatment strategies involving pancreas transplantation should be considered for patients with frequent metabolic complications of diabetes and for those patients who favor kidney-pancreas transplantation over kidney transplantation alone. For patients without a living donor, simultaneous pancreas-kidney transplantation is associated with the greatest life expectancy.

Short-term combination of mycophenolate mofetil with cyclosporine as a therapeutic option for renal transplant recipients: A prospective, multicenter, randomized study

BACKGROUND

Mycophenolate mofetil (MMF), compared to azathioprine (AZA), reduces acute rejection and treatment failure in cyclosporine (CsA) and steroid regimens, but its effect on graft survival is unproven from prospective studies and prolonged use is costly. This study evaluated the efficacy and tolerability of replacing MMF by AZA after 3 months.

METHODS

This 28 center, prospective, 12-month, parallel group, open-label study, randomized patients to three groups with microemulsion formulation of CsA (ME-CsA) and steroids as baseline therapy. Group 1 (n=158) received MMF for 3 months, replaced by AZA for 9 months; group 2 (n=162) received MMF for 12 months; and group 3 (n=157) received AZA for 12 months.

RESULTS

Treatment failure and the cumulative rate of acute rejection were significantly lower in the MMF groups compared with the AZA group (P=0.007 and P=0.03, respectively). Graft loss, death, and safety profiles of all three treatments were similar over 12 months, as were mean serum creatinine levels. Switching from MMF to AZA did not affect treatment failure. No patient in group 1 experienced a recurrent rejection after month 3, one patient died, and nine patients experienced first rejection episodes. Most rejections (6/9) were steroid-sensitive and histologically mild.

CONCLUSIONS

Replacement of MMF by AZA after 3 months of therapy with ME-CsA and steroids provides comparable efficacy and safety profiles to continuous MMF over 12 months. Although apparently a cost-effective option, long-term studies are required to assess the benefit/risk ratio of this therapy switch in different patient subpopulations.

Mycophenolate mofetil: a pharmacoeconomic review of its use in solid organ transplantation

Most pharmacoeconomic studies of mycophenolate mofetil have focused on its use as part of maintenance immunosuppression for renal transplantation, involving short-term (3 to 12 months) time frames. In general, mycophenolate mofetil reduced the treatment costs for rejection episodes and graft failure which offset its higher drug acquisition cost compared with azathioprine. Several cost analyses have been modelled on the large multicentre trials of adult renal transplant recipients. The use of mycophenolate mofetil was associated with either cost savings or no additional costs after 6 or 12 months in French, US and Canadian analyses of triple or quadruple immunosuppressant therapy. A further cost analysis utilising a registry database of renal transplant recipients in the US found mycophenolate mofetil to be cost saving compared with azathioprine after 6.4 years when evaluating costs due to graft loss only. Of the limited cost-effectiveness analyses with the drug, one US study modelled the 1- and 10-year cost effectiveness of mycophenolate mofetil and various other immunosuppressants used in combined regimens. Long-term use of mycophenolate mofetil was less cost effective than other regimens, but the use of long-term mycophenolate mofetil in high-risk patients was shown to be a relatively cost-effective strategy. In another US analysis comparing mycophenolate mofetil with azathioprine as part of quadruple therapy, mycophenolate mofetil was associated with slightly lower costs during the first year after renal transplantation as well as improved clinical outcomes.

CONCLUSION

Pharmacoeconomic studies support the use of mycophenolate mofetil as part of immunosuppressant therapy in renal transplantation, at least in the short term. Although the cost effectiveness of mycophenolate mofetil in the long term is less clear, limited pharmacoeconomic data available appear promising. Among issues to be examined in future economic analyses in renal transplantation are the calcineurin-sparing potential of mycophenolate mofetil and the feasibility of using more efficient mycophenolate mofetil dosage regimens when using the drug on a long-term basis. Additional pharmacoeconomic analyses of mycophenolate mofetil are also needed in other types of solid organ transplantation.

Mycophenolate mofetil: suggested guidelines for use in kidney transplantation

Mycophenolate mofetil (MMF) is an immunosuppressive drug designed to inhibit inosine monophosphate dehydrogenase (IMPDH). IMPDH is a key enzyme in the de novo purine synthesis of lymphocytes. It is crucially important for proliferative responses of human T and B lymphocytes. The inhibition of IMPDH thus leads to selective lymphocyte suppression. After successful use in various in vitro and animal models, MMF was brought to clinical trial in patients undergoing transplantation. The drug is rapidly and completely absorbed following oral administration. Pilot studies of administration with cyclosporin and corticosteroids suggested a significant reduction in the incidence of organ rejection at dosages of 1 to 3 g/day. As a result of these studies, 3 pivotal randomised double-blind multicentre trials, involving nearly 1500 patients, were designed to investigate the effects of addition of MMF to different standard immunosuppressive protocols on the prevention of acute renal allograft rejection. After 6 months, the rates of biopsy-proven rejection were significantly reduced in patients receiving MMF. In combination with cyclosporin and corticosteroids, the adverse effect profile resembled that of azathioprine. Most adverse effects were associated with the gastrointestinal tract, the blood system and opportunistic infections. MMF offers improved immunosuppressive therapy following renal and probably other solid organ transplantation. MMF has been licensed since 1995 for the prevention of acute renal allograft rejection in most countries. It has been used in different combinations of immunosuppressive drugs and in various dosages and regimens.

Treatment of systemic lupus erythematosus with mycophenolate mofetil

Mycophenolate mofetil is an immunosuppressive drug that is of established efficacy in renal transplantation. It inhibits the de novo pathway of purine synthesis and therefore lymphocyte proliferation. Mycophenylate mofetil has been shown to ameliorate the severity of renal injury in murine models of lupus nephritis. Recent studies suggest that it may also be effective in the treatment of patients with lupus nephritis when used in conjunction with steroids. These observations need to be confirmed in adequately sized randomised-controlled studies.

Randomized trial of conversion from mycophenolate mofetil to azathioprine 6 months after renal allograft transplantation

BACKGROUND

In the first year after renal allograft transplantation, triple therapy immunosuppression with cyclosporin (CsA), prednisone (P), and mycophenolate mofetil (MMF) is superior to a triple therapy treatment that includes azathioprine (AZA) instead of MMF. Whether long-term treatment with CsA-P-MMF is better than treatment with CsA-P-AZA is a matter of debate, as 3-year graft survival is similar in MMF- and AZA-treated patients. The purpose of the present study was to examine the short-term effect of changing MMF to AZA in low-risk renal allograft recipients 6 months after transplantation.

METHOD

This was a randomized, open-label single-centre study, recruiting 48 low risk renal allograft recipients on CsA-P-MMF therapy 6 months after transplantation, comparing the outcome with continued MMF treatment (2 g b.i.d.) (group A, n=22) or switching MMF to AZA (1 mg/kg) treatment (group B, n=26).

RESULTS

The outcome after a 6-months follow-up of patients in group A and group B was similar. Treatment failure rates (defined as clinically diagnosed acute rejection episodes) were 4.5% in group A and 3.8% in group B. There were no patient deaths and no graft failures during the 6-months observation period. Graft function was excellent and similar in both groups.

CONCLUSION

Replacing MMF with AZA 6 months after transplantation in low-risk renal allograft recipients is safe and is not associated with altered graft function in the short term.

A comparative analysis of the use of mycophenolate mofetil in pediatric vs. adult renal allograft recipients

Mycophenolate mofetil (MMF) is a new immunosuppressive drug used in combination with cyclosporin A (CsA) or tacrolimus and prednisone to prevent rejection of renal allografts in both adult and pediatric recipients. It has been shown in several large studies that MMF significantly decreases the incidence of acute rejection in adults and has acceptable adverse effects. In this retrospective study, we compare the incidence of adverse events between pediatric and adult renal allograft recipients. Twenty-two children and 37 adult renal allograft recipients were included in the study. The initial dose of MMF was 1.5 g b.i.d. for the adult patients and ranged from 15 to 30 mg/kg/d for the pediatric patients. All patients received p.o. acyclovir as prophylaxis for cytomegalovirus (CMV). The two groups were similar regarding gender distribution and graft source. Acute rejections occurred in 10 of the 22 pediatric patients (45%) and in nine of the 37 adults (24%), p = NS. The incidence of infections was similar in both groups except for the occurrence of CMV (n = 5), which was seen only in adults. The incidence of GI symptoms was significantly higher in the pediatric population (54.5% vs. 21.6%; p = 0.02). Significant weight loss was seen more often in the smaller pediatric patients (weight < or = 15 kg) compared to the larger pediatric patients, 60% vs. 11.7%, p = 0.05. Among the patients who had significant GI symptoms 50% of the adults and 75% of the pediatric recipients required either dose reduction or, most commonly, discontinuation of the MMF. The need to discontinue MMF was significantly higher in the pediatric patients, especially in those that weighed less than 15 kg. We suggest the possibility that the optimum dose, dosing interval or preparation of MMF has not yet been established for pediatric patients. One should therefore monitor pediatric patients closely, especially the small ones, to avoid significant nutritional problems and other adverse GI events.