Pharmacokinetic monitoring of mycophenolic acid in heart transplant patients: correlation the side-effects and rejections with pharmacokinetic parameters.

BACKGROUND: Mycophenolate mofetil is a commonly used immunosuppressant in heart transplantation but pharmacokinetic monitoring is not routinely done. We performed a prospective pilot multi-center trial in de-novo heart transplant recipients to evaluate the pharmacokinetics (PK) of mycophenolic acid (MPA) at multiple time points in the first year following transplant.
MATERIAL/METHODS: MPA trough and estimated area-under-the-curve (AUC) values were obtained at multiple visits from 21 enrolled patients. We attempted to correlate the side-effects and rejections with PK parameters.
RESULTS: MPA AUC and trough levels increased modestly over 12 months with substantial inter and intra patient variability. Cardiac rejection was associated with low MPA AUC values with a threshold of <36.2 mg×h/L during the first two post-transplant weeks. A threshold of 2-weeks average MPA trough level of 1.43 mg/L provided a sensitivity 82% and a specificity of 60%.
CONCLUSIONS: Adequate MPA levels are associated with decreased risk of allograft rejection. For patients with Cyclosporine co-immunosuppression, we propose an MPA trough of 1.4 mg/L and an MPA AUC of 36 mg × h/L as threshold values for dose adjustments. We recommend monitoring MPA levels at 1, 2 and 4 weeks, 6 months, 1 year and whenever an unexplained side-effect or allograft rejection occurs. Additional MPA AUC measurements are recommended when trough levels do not explain the clinical picture.

Impact of changing from cyclosporine to tacrolimus on pharmacokinetics of mycophenolic acid in renal transplant recipients with diabetes.

The rate of mycophenolic acid (MPA) absorption after oral administration of mycophenolate mofetil (MMF) is delayed in patients with diabetes. Cyclosporine (CsA) decreases MPA exposure by inhibiting enterohepatic recirculation of MPA/MPA glucuronide, and tacrolimus (TRL) may alter the rate and extent of MPA absorption due to its prokinetic properties especially in patients with diabetic gastroparesis. This study evaluated the effect of changing from CsA to TRL on pharmacokinetics of MPA in stable renal transplant recipients with long-standing diabetes. Eight patients were switched from a stable dose of CsA to TRL while taking MMF 1 g twice daily. The 12-hour steady-state total plasma concentration-time profiles of MPA and MPA glucuronide were obtained after oral administration of MMF on 2 occasions: first while taking CsA and second after changing to TRL. Pharmacokinetic parameters of MPA were calculated by the noncompartmental method. Changing from CsA to TRL resulted in significantly increased MPA exposure (area under the concentration-time curve from 0 to 12 hours, AUC0-12) by 46 +/- 32% (P = 0.012) and MPA predose concentration (C0) by 121 +/- 67% (P = 0.008). The magnitude of change in MPA exposure did not correlate well with MPA-C0 or CsA trough concentration. Switching to TRL had minimal impact on peak concentration of MPA (15.0 +/- 6.9 mg/L with CsA versus 16.1 +/- 9.7 mg/L with TRL, P = 0.773) and time to reach the peak concentration (1.0 +/- 0.4 hours with CsA versus 1.2 +/- 0.8 hours with TRL, P = 0.461). Highly variable and unpredictable changes in MPA exposure among renal transplant patients with diabetes do not support a strategy of preemptively adjusting MMF dose when switching calcineurin inhibitors in this population.

Lack of an effect of oral iron administration on mycophenolic acid pharmacokinetics in stable renal transplant recipients.

STUDY OBJECTIVES: To determine if coadministration of polysaccharide iron complex and slow-release ferrous sulfate alter the absorption of mycophenolic acid (MPA), and to examine the potential influence of dosing relative to mycophenolate mofetil (MMF) administration and the effect of immediate- versus sustained-release iron products on the steady-state pharmacokinetics of MPA. DESIGN: Prospective, open-label, three-phase, crossover, steady-state pharmacokinetic study. SETTING: National Institutes of Health-sponsored General Clinical Research Center at a university medical center. PATIENTS: Twelve adult (mean age 50 yrs) renal transplant recipients who were receiving concomitant iron and MMF maintenance therapy. INTERVENTION: Oral iron therapy was coadministered with MMF on days -6-0, MMF was administered alone on days 1-8 (control phase), then oral iron therapy was administered 2 hours after MMF administration on days 9-16. MEASUREMENTS AND MAIN RESULTS: Baseline demographics, concurrent drug regimens, and clinical laboratory values were assessed. Blood samples were obtained at baseline and at 1, 2, 3, 4, 6, 8, and 12 hours after MMF administration on days 0, 8, and 16. The MPA levels were measured by high-performance liquid chromatography. We found no significant differences in the dose-standardized area under the concentration-time curve from 0-12 hours (AUC(0-12)) for MPA between the control phase (39.66 +/- 8.70 mg mg x hr/L) and the concomitant ferrous sulfate or dose-separated ferrous sulfate (37.56 +/- 9.95 or 32.84 +/- 8.43 mg x hr/L, respectively, p>0.05) phases. Dose-standardized AUC(0-12) values for MPA did not significantly differ after the concomitant administration of polysaccharide iron complex from that of the control phase (48.46 +/- 9.68 and 43.80 +/- 9.46 mg x hr/L, respectively, p=0.065). However, the AUC(0-12) for MPA significantly increased when polysaccharide iron complex was administered 2 hours after MMF (53.41 +/- 11.75 mg x hr/L, p=0.012). Maximum concentrations and times to reach maximum concentrations remained consistent across all study phases in each arm of the trial (p>0.05). CONCLUSION: Multiple doses of iron therapy-slow-release ferrous sulfate, or polysaccharide iron complex-did not significantly reduce systemic exposure to MMF, as measured by using AUC(0-12) values.

Rabbit antithymocyte globulin versus basiliximab in renal transplantation.

BACKGROUND: Induction therapy reduces the frequency of acute rejection and delayed graft function after transplantation. A rabbit antithymocyte polyclonal antibody or basiliximab, an interleukin-2 receptor monoclonal antibody, is most commonly used for induction. METHODS: In this prospective, randomized, international study, we compared short courses of antithymocyte globulin and basiliximab in patients at high risk for acute rejection or delayed graft function who received a renal transplant from a deceased donor. Patients taking cyclosporine, mycophenolate mofetil, and prednisone were randomly assigned to receive either rabbit antithymocyte globulin (1.5 mg per kilogram of body weight daily, 141 patients) during transplantation (day 0) and on days 1 through 4 or basiliximab (20 mg, 137 patients) on days 0 and 4. The primary end point was a composite of acute rejection, delayed graft function, graft loss, and death. RESULTS: At 12 months, the incidence of the composite end point was similar in the two groups (P=0.34). The antithymocyte globulin group, as compared with the basiliximab group, had lower incidences of acute rejection (15.6% vs. 25.5%, P=0.02) and of acute rejection that required treatment with antibody (1.4% vs. 8.0%, P=0.005). The antithymocyte globulin group and the basiliximab group had similar incidences of graft loss (9.2% and 10.2%, respectively), delayed graft function (40.4% and 44.5%), and death (4.3% and 4.4%). Though the incidences of all adverse events, serious adverse events, and cancers were also similar between the two groups, patients receiving antithymocyte globulin had a greater incidence of infection (85.8% vs. 75.2%, P=0.03) but a lower incidence of cytomegalovirus disease (7.8% vs. 17.5%, P=0.02). CONCLUSIONS: Among patients at high risk for acute rejection or delayed graft function who received a renal transplant from a deceased donor, induction therapy consisting of a 5-day course of antithymocyte globulin, as compared with basiliximab, reduced the incidence and severity of acute rejection but not the incidence of delayed graft function. Patient and graft survival were similar in the two groups. (ClinicalTrials.gov number, NCT00235300 [ClinicalTrials.gov].).

Efficacy and safety of low-dose valganciclovir in the prevention of cytomegalovirus disease in adult liver transplant recipients.

The efficacy and safety of valganciclovir (VGCV) for cytomegalovirus (CMV) prophylaxis in liver transplant recipients has not been established. We retrospectively compared the efficacy and safety of low-dose oral VGCV (450 mg once daily for 90 days) and standard oral ganciclovir (1 g three times a day for 90 days, GCV) in preventing CMV disease in 109 adult liver transplant recipients who survived at least 1 month between January 2001 and April 2003 (49 GCV and 60 VGCV). The incidence of CMV disease at 1 year post-transplant was similar among patients treated with VGCV and GCV (3% and 4%, respectively). Three of the four CMV disease cases occurred in high-risk recipients with CMV serotype of donor+/recipient- (D+/R-) and all cases presented after completion of CMV prophylaxis, ranging 114-152 days post-transplant. Severe neutropenia was rare, and thrombocytopenia and anemia occurred at similar frequencies with both prophylaxis regimens. In conclusion, a 90-day regimen of low-dose oral VGCV has a similar efficacy and safety profile to high-dose oral GCV in adult liver transplant recipients. D+/R- liver transplant recipients remain at risk of developing CMV disease after completion of antiviral prophylaxis. Additional prospective studies with close monitoring for CMV viremia and drug resistance are needed to further establish the optimal dose and duration of VGCV in liver transplant recipients.

Effect of oral vitamin E and C therapy on calcineurin inhibitor levels in heart transplant recipients.

BACKGROUND: A recent prospective trial demonstrated that oral vitamins C and E retard the early progression of transplant-associated coronary arteriosclerosis; as a result, a number of centers have added these agents to their maintenance regimens. This study reviewed the impact of vitamin E and C supplementation on calcineurin inhibitor trough concentrations. METHODS: A retrospective chart review of the first 29 heart transplant patients prescribed anti-oxidant agents was performed. Twenty-two patients taking cyclosporin A (CsA) and 7 patients taking tacrolimus were prescribed vitamin C (500 mg twice a day) and vitamin E (400 IU twice a day). Serum chemistries and drug levels were measured before and after vitamin therapy was initiated. RESULTS: The baseline CsA trough concentration (mean +/- SD) was 137 +/- 39 ng/ml and it declined to 99 +/- 54 ng/ml (p = 0.007) after anti-oxidant therapy was initiated. The average percentage decrease in the CsA trough concentration was 30%. No significant changes were seen in the patients taking tacrolimus. CONCLUSIONS: These data demonstrate that supplementation with the anti-oxidant agents vitamin C and vitamin E decreases CsA concentrations but does not appear to effect tacrolimus concentrations. Although more detailed pharmacokinetic analysis is necessary to clarify the exact mechanism of this interaction, physicians who take care of transplant recipients should be aware that more frequent CsA concentration monitoring is warranted after initiating these anti-oxidant agents.

Reproduction and transplantation: report on the AST Consensus Conference on Reproductive Issues and Transplantation.

It has been almost 50 years since the first child was born to a female transplant recipient. Since that time pregnancy has become common after transplantation, but physicians have been left to rely on case reports, small series and data from voluntary registries to guide the care of their patients. Many uncertainties exist including the risks that pregnancy presents to the graft, the patient herself, and the long-term risks to the fetus. It is also unclear how to best modify immunosuppressive agents or treat rejection during pregnancy, especially in light of newer agents available where pregnancy safety has not been established. To begin to address uncertainties and define clinical practice guidelines for the transplant physician and obstetrical caregivers, a consensus conference was held in Bethesda, Md. The conferees summarized both what is known and important gaps in our knowledge. They also identified key areas of agreement, and posed a number of critical questions, the resolution of which is necessary in order to establish evidence-based guidelines. The manuscript summarizes the deliberations and conclusions of the conference as well as specific recommendations based on current knowledge in the field.

Statin use and risks of death or fatal rejection in the Heart Transplant Lipid Registry.

Although small, randomized trials have shown that statin use is associated with decreased risks of mortality and severe rejection, no study has examined statin therapy as used in actual practice in large numbers of heart transplant recipients. We analyzed data from the Heart Transplant Lipid Registry (n = 12 centers). Patients were included if they underwent transplantation between 1995 and 1999, survived >/=30 days after transplantation, and had >/=30 days of Registry follow-up. Multivariable Cox regression models, with propensity scoring performed to adjust for nonrandom allocation of statin therapy, were performed to determine the association of statin therapy with death and fatal rejection. The study included 1,186 patients, with a mean follow-up of 580 +/- 469 days; 937 patients (79%) received statin therapy. Overall, 71 patients (6%) died and 40 (3.4%) had fatal rejection. The statin group had a lower frequency of death (4% vs 13.7%, p <0.0001) and fatal rejection (2.4% vs 7.2%, p = 0.0001). Using multivariable Cox regression, with propensity scoring included to adjust for likelihood of receiving statin therapy, statin use was the only factor associated with lower risk of death (hazard ratio 0.29, 95% confidence interval 0.13 to 0.67) and fatal rejection (hazard ratio 0.27, 95% confidence interval 0.09 to 0.78). This study represents the largest population of heart transplant recipients analyzed for the relation between statin therapy and clinical outcomes in actual practice. Statin therapy was significantly associated with lower risk of death and fatal rejection, benefits that were independent of lipid values.

Lack of correlation between MMF dose and MPA level in pediatric and young adult cardiac transplant patients: does the MPA level matter?

To determine the correlation between mycophenolate mofetil (MMF) dose and mycophenolic acid (MPA) level as well as its impact on rejection among young cardiac transplant recipients (OHT), trough concentrations of MPA and its metabolite, mycophenolic acid glucuronide (MPAG), were measured following MMF doses of 1200 mg/m2/d (max 3000 mg/d). Corresponding endomyocardial biopsy (EMB) grades and calcineurin inhibitor levels were recorded with simultaneous MPA/MPAG levels. Correlation coefficients were derived between MMF dose and MPA/MPAG levels. Contingency analysis evaluated the relation between MPA level and EMB score. Twenty-six patients (median age 15.4 years) had 120 MPA/MPAG levels measured. Average MMF dose was 1208.8 mg/m2/d with median MPA and MPAG concentrations: 2.1 (therapeutic: 1.0-3.5 microg/mL) and 48 microg/mL (reference range: 35-100 microg/mL), respectively. Only 50% of patients consistently achieved therapeutic levels with standard dosing. No correlation was found between MMF dose and MPA/MPAG levels. In the presence of therapeutic calcineurin inhibition, EMB grade > or = 2 occurred more with MPA concentrations < 2.5 microg/mL (p = 0.01). In young OHT patients, MMF dose does not correlate with MPA/MPAG levels, and standard MMF dosing fails to consistently achieve 'therapeutic' MPA concentrations. An MPA trough level < 2.5 microg/mL was more frequently associated with EMB grade > or = 2. Concentration rather than dose-driven management is a more prudent strategy when using MMF.

New prophylactic treatment strategy for cytomegalovirus disease.

The pharmacology, pharmacokinetics, safety, and efficacy of valganciclovir, an oral prodrug for ganciclovir, used to prevent cytomegalovirus (CMV) disease in solid organ transplant recipients are described. Valganciclovir was developed to overcome the disadvantages associated with ganciclovir, which include low oral bioavailability, limited efficacy because of the development of viral resistance, and the need for frequent administration, which can adversely affect patient adherence. Valganciclovir is rapidly converted to ganciclovir; systemic exposure to the parent drug is low and short in duration. The oral bioavailability of ganciclovir from valganciclovir is 10 times higher than that from the original ganciclovir formulation. Food increases the oral bioavailability of valganciclovir. In a four-way, randomized, crossover pharmacokinetic study of 28 liver transplant recipients, single doses of valganciclovir 900 mg and intravenous ganciclovir 5 mg/kg resulted in a similar ganciclovir systemic exposure. The systemic exposure was proportionately lower with a single 450-mg dose of valganciclovir but similar to that of oral ganciclovir 3 g administered in three divided doses. In the recent multicenter, randomized, double-blind, double-dummy PV16000 trial in 364 solid organ transplant recipients at high risk for CMV disease (i.e., CMV-negative recipients of CMV-positive donor organs), valganciclovir 900 mg once daily was as effective in preventing CMV-disease as oral ganciclovir 1 g three times daily. Resistance was reported with ganciclovir but not with valganciclovir. Both drugs were well tolerated.

Safety and efficacy of atorvastatin in heart transplant recipients.

BACKGROUND: Pravastatin and simvastatin prolong survival and reduce transplant-related coronary vasculopathy, although low-density lipoprotein (LDL) lowering with these agents is only modest. The objective of this study was to assess the safety of moderate dose atorvastatin and its efficacy when prior treatment with another statin had failed to lower LDL to < 100 mg/dl. METHODS: Data from 185 patients were retrospectively evaluated for adverse events, duration of exposure (person-days), and the mean atorvastatin dose exposure. Changes in lipid parameters, and prednisone and cyclosporine doses were determined. SAFETY: 48 patients received atorvastatin for 24,240 person-days at a mean dose exposure of 21 +/- 10 mg. Rhabdomyolysis, myositis, myalgias, and hepatotoxicity occurred in 0, 2, 2, and 0 patients, respectively. All events occurred at the 10-mg dose, within the first 3 months, and were rapidly reversible with atorvastatin discontinuation. EFFICACY: Thirty-four patients evaluable for efficacy analyses had a pre-atorvastatin LDL of 145 +/- 38 mg/dl on the following statins: pravastatin (n = 30, 40 +/- 0mg), fluvastatin (n = 3, 33 +/- 12 mg), simvastatin (n = 1, 40 mg). After atorvastatin (21 +/- 9 mg/day) for 133 +/- 67 days, LDL was reduced to 97 +/- 24 mg/dl (relative reduction 31 +/- 20%, p < 0.0001). At the end of the observation period (418 +/- 229 days, atorvastatin final dose 24 +/- 14 mg/day), LDL was further decreased to 88 +/- 23 mg (relative reduction 37 +/- 17%, p < 0.0001). CONCLUSION: Atorvastatin, when used at moderate doses and with close biochemical and clinical monitoring, appears to be safe and is effective in aggressively lowering LDL in heart transplant recipients when treatment with other statins has failed to achieve LDL goals.