[Optimal immunosuppressive therapy based on pharmacokinetics and pharmacodynamics of antimetabolites in clinical practice]

Drug-Induced Hematological Cytopenia in Kidney Transplantation and the Challenges It Poses for Kidney Transplant Physicians

Drug-induced hematological cytopenia is common in kidney transplantation. Various cytopenia including leucopenia (neutropenia), thrombocytopenia, and anemia can occur in kidney transplant recipients. Persistent severe leucopenia or neutropenia can lead to opportunistic infections of various etiologies. On the contrary, reducing or stopping immunosuppressive medications in these events can provoke a rejection. Transplant clinicians are often faced with the delicate dilemma of balancing cytopenia and rejection from adjustments of immunosuppressive regimen. Differentials of drug-induced cytopenia are wide. Identification of culprit medication and subsequent modification is also challenging. In this review, we will discuss individual drug implicated in causing cytopenia and correlate it with corresponding literature evidence.

Spectroscopic investigation for the interaction of mycophenolate mofetil with ferrous ions

The interaction of mycophenolate mofetil (MMF) with ferrous ions (Fe(2+)) in the solid state, in water, and in polar organic solvents was investigated using (1)H-NMR, (13)C-NMR, IR, and UV-visible (Vis) spectroscopies. A red-purple colored substance was formed after grinding solid MMF and FeSO4·7H2O in a mortar. The IR spectrum of taken as a KBr tablet of the colored substance showed a new absorption band at 1651 cm(-1). Although the color disappeared when the sample was dissolved in water, it persisted in organic solvents such as MeOH or dimethyl sulfoxide (DMSO). The UV-Vis spectrum of a 0.25 mM MeOH solution of MMF showed a new absorption maximum at 507 nm in the presence of Fe(2+) ions, while an aqueous solution of the same mixture showed no significant change from the MMF solution. All the signals in the (13)C-NMR spectrum in DMSO-d6 solution were unambiguously assigned. Upon the addition of 0.5 eq. of Fe(2+) ions, all the carbon signals except those of the 2-morpholinoethyl group almost disappeared, which clearly indicated that the Fe(2+) ions were located far away from the 2-morpholinoethyl groups in the MMF molecules. On the basis of these results, we have concluded that the MMF-Fe(2+) complex is actually formed in the solid state as well as in polar organic solvents such as MeOH or DMSO.

Safety of reduced dose of mycophenolate mofetil combined with tacrolimus in living-donor liver transplantation

Background/Aims

The dose of mycophenolate mofetil (MMF) has been reduced in Asia due to side effects associated with the conventional fixed dose of 2-3 g/day. We aimed to determine the pharmacokinetics of a reduced dose of MMF and to validate its feasibility in combination with tacrolimus in living-donor liver transplantation (LDLT).

Methods

Two sequential studies were performed in adult LDLT between October 2009 and 2011. First, we performed a prospective pharmacokinetic study in 15 recipients. We measured the area under the curve from 0 to 12 hours (AUC_0-12) for mycophenolic acid at postoperative days 7 and 14, and we performed a protocol biopsy before discharge. Second, among 215 recipients, we reviewed 74 patients who were initially administered a reduced dose of MMF (1.0 g/day) with tacrolimus (trough, 8-12 ng/mL during the first month, and 5-8 ng/mL thereafter), with a 1-year follow-up. We performed protocol biopsies at 2 weeks and 1 year post-LDLT.

Results

In the first part of study, AUC_0-12 was less than 30 mgh/L in 93.3% of cases. In the second, validating study, 41.9% of the recipients needed dose reduction or cessation due to side effects within the first year after LDLT. At 12 months post-LDLT, 17.6% of the recipients were administered a lower dose of MMF (0.5 g/day), and 16.2% needed permanent cessation due to side effects. The 1- and 12-month rejection-free survival rates were 98.6% and 97.3%, respectively.

Conclusions

A reduced dose of MMF was associated with low blood levels compared to the existing recommended therapeutic range. However, reducing the dose of MMF combined with a low level of tacrolimus was feasible clinically, with an excellent short-term outcome in LDLT.