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Immunosuppressive drugs for solid organ transplantation are critical dose drugs with a narrow therapeutic index. Many of the most commonly used innovator drugs are off patent and have been replicated by generic counterparts, often at substantial cost-savings to the patient. However, serious adverse events caused by the transition from innovator to generic medications, specifically in pediatric solid organ transplant recipients, have questioned these autosubstitutions. The purpose of this review is to summarize the criteria set forth by the regulatory bodies, and to examine how major immunosuppressive drugs conform to these recommendations. Regulatory bodies have established inconsistent criteria to demonstrate bioequivalence between innovator and generic medications, causing approved generic variations to have varying levels of equivalence with the innovator drugs. In order to minimize the risk for under-immunosuppression, the following recommendations have been concluded. Brand prescribing of cyclosporine and tacrolimus are recommended due to evidence of adverse events after conversion to generic formulations and differences in dissolution parameters. Mycophenolate mofetil (MMF) shows better bioequivalence between innovator and generic formulations, however caution should be advised when switching between formulations. The institution of 'innovator only' policies may be appropriate at this time in order to minimize the risk of under-immunosuppressing patients until the evidence of more stringent bioequivalence has been established.

Mycophenolate mofetil (MMF) has recently been introduced as an immunosuppressive agent for the treatment of glomerulonephritis with systemic lupus erythematosus (SLE) and the data have been encouraging. However, response to MMF treatment appears to differ ethnically. Therefore, we determined efficacy and safety of low-dose MMF for Taiwanese patients with lupus nephritis. We studied 36 lupus nephritis patients who were treated with MMF. The dose started at 0.5 g/day and we collected the data from patients who received up to 1 g/day MMF. Outcome measures were 24 h for proteinuria, serum creatinine, C3/C4 levels, and anti-dsDNA titers collected at the baseline and at 3-month treatment intervals. Daily urinary protein significantly decreased from 6.15 +/- 4.28 g to 2.69 +/- 2.36 g at the last visit (P < 0.01) in spite of the significant absence of changes in serum creatinine levels. The response rate was 65.7% including five (14.3%) cases of complete remission and 18 (51.4%) cases of partial remission. The concomitant oral prednisolone dose decreased significantly from 20.07 +/- 11.78 mg/day to 13.93 +/- 6.79 mg/day at 6 months (P < 0.01). The level of C3 increased significantly from 59.46 +/- 32.73 to 71.99 +/- 25.81 (P < 0.01) and the anti-dsDNA antibody titer decreased from 161.71 +/- 221.42 to 46.57 +/- 117.47 (P < 0.01). No severe adverse effects were observed in the study. Low-dose MMF (0.5 to 1 g/day) combined with glucocorticoids appears to be a safe and effective therapy for lupus nephritis in Taiwanese patients. Our results suggest that lupus nephritis in Oriental patients might respond to lower doses of MMF than Caucasians.

Data on exposure to mycophenolic acid (MPA), the active moiety of mycophenolate mofetil (MMF), in pediatric renal transplant recipients beyond the first year posttransplant are scarce. The authors therefore analyzed the long-term pharmacokinetics of MPA in 25 pediatric patients treated with 600 mg MMF/m body surface area twice a day in conjunction with cyclosporine A and prednisone. Plasma samples for 12-hour pharmacokinetic profiles were collected on day 7, and after 3, 9, 24, and 36 months posttransplant. Both the actual and the dose-normalized MPA-area under the concentration-time curve (AUC0-12) increased approximately 2-fold between day 7 and month 9 but stabilized thereafter. Both the actual and the dose-normalized MPA-AUC0-12 at months 24 and 36 were comparable to that at month 9. Presuming a therapeutic window of 30-60 mg h/L, 15 (60%) of 25 patients at day 7 had an MPA-AUC0-12 <30 mg h/L, indicating potential underexposure, whereas the proportion of patients with an MPA-AUC0-12 <30 mg h/L between months 3 and 36 was low (5%-17%). These data suggest that the recommended MMF dose of 600 mg/m body surface area twice a day in conjunction with cyclosporine A leads to MPA underexposure early posttransplant in a significant subset of patients, indicating a need for a higher initial MMF dose. Dose-normalized MPA exposure increases in the first 9 months posttransplant, consistent with a reduced MPA metabolism and increased enterohepatic recycling of MPA.

RS-61443, a morpholinoethyl ester of mycophenolic acid, inhibits the synthesis of guanosine monophosphate, which plays a pivotal role in lymphocyte metabolism. The drug blocks proliferative responses of T and B lymphocytes, and inhibits antibody formation and the generation of cytotoxic T cells. In vivo, RS-61443 prolongs the survival of islet allografts in mice, heart allografts in rats, and kidney allografts in dogs. Reversal of ongoing acute rejection was demonstrated in rat heart allografts and kidney allografts in dogs. Preliminary evidence suggests that the drug prevents chronic rejection. The purpose of this study was to test the safety and tolerance in patients receiving primary cadaver kidneys. RS-61443 in doses from 100 mg/day p.o. to 3500 mg/day p.o. was given to patients in combination with cyclosporine and prednisone. Further study goals were to evaluate the pharmacokinetics of RS-61443, watch for the occurrence of opportunistic infections and acute rejection, and establish dosages for further clinical trials. Forty-eight patients were entered, with six patients in each dose group. RS-61443 was well tolerated in all dose groups, with only one adverse event possibly related to the drug (hemorrhagic gastritis). There was a statistically significant correlation between rejection episodes and dose (P = 0.022), patients with rejection episodes versus dose (P = 0.038), and number of OKT3/prednisone courses versus dose (P = 0.008). There was no overt nephrotoxicity or hepatotoxicity. Preliminary results of a rescue trial in 20 patients with kidney transplants will also be presented.