Pharmacodynamic Monitoring of Inosine Monophosphate Dehydrogenase Activity: A Basis For Optimized and Individualized Mycophenolate Mofe

In 1896 Gosic isolated for the first time mycophenolic acid (MPA) from Penicillium glaucum.It was subsequently isolated from Penicillium stoloniferum Thom (synonym P. brevi-compactum Dierckx) by Alsberg and Black in 1913 who gave the acid phenolic substance its name mycophenolic acid (MPA).From 1931 to 1933 a series of studies in the biochemistry of micro-organisms was published by Clutterbuck, Raistrick and Oxford of the division of biochemistry from the University of London. These series described in detail the isolation and characterization of MPA. The structure of MPA was finally established in 1952. In the first decades, MPA was eventually found to have antineoplastic, antibacterial, antifungal and antiviral properties and was investigated by a few groups.In 1969, Planterose et al described an effect of MPA most likely to an immunosuppressive effect, and Mitsui et al reported in the same year for the first time the immunosuppressive effect of MPA in mice, at the cellular and humoral levels of antibody formation. In the following years, more and more research was done on the efficacy of MPA as an immunosuppressant. Mycophenolate mofetil (MMF) was developed at Syntex Corporation to be a more bioavailable form of MPA. The first human trials of MMF in kidney recipients were conducted by Sollinger et al, leading to the registration of the pharmaceutical compound as immunosuppressant in 1995

The effect of a transitional pharmaceutical care program on the occurrence of ADEs after discharge from hospital in patients with polypharmacy

Introduction: Transitional care programs (i.e. interventions delivered both in hospital and in primary care), could increase continuity and consequently quality of care. However, limited studies on the effect of these programs on Adverse Drug Events (ADEs) post-discharge are available. Therefore, the aim of this study was to investigate the effect of a transitional pharmaceutical care program on the occurrence of ADEs 4 weeks post-discharge. Methods: A multicentre prospective before-after study was performed in a general teaching hospital, a university hospital and 49 community pharmacies. The transitional pharmaceutical care program consisted of: teach-back to the patient at discharge, a pharmaceutical discharge letter, a home visit by a community pharmacist and a clinical medication review by both the community and the clinical pharmacist, on top of usual care. Usual care consisted of medication reconciliation at admission and discharge by pharmacy teams. The primary outcome was the proportion of patients who reported at least 1 ADE 4 weeks post-discharge. Multivariable logistic regression was used to adjust for potential confounders. Results: In total, 369 patients were included (control: n = 195, intervention: n = 174). The proportion of patients with at least 1 ADE did not statistically significant differ between the intervention and control group (general teaching hospital: 59% vs. 67%, ORadj 0.70 [95% CI 0.38–1.31], university hospital: 63% vs 50%, OR adj 1.76 [95% CI 0.75–4.13]). Conclusion: The transitional pharmaceutical care program did not decrease the proportion of patients with ADEs after discharge. ADEs after discharge were common and more than 50% of patients reported at least 1 ADE. A process evaluation is needed to gain insight into how a transitional pharmaceutical care program could diminish those ADEs

Pharmacokinetic role of protein binding of mycophenolic acid and its glucuronide metabolite in renal transplant recipients

Mycophenolic acid (MPA), the active compound of mycophenolate mofetil (MMF), is used to prevent graft rejection in renal transplant recipients. MPA is glucuronidated to the metabolite MPAG, which exhibits enterohepatic recirculation (EHC). MPA binds for 97% and MPAG binds for 82% to plasma proteins. Low plasma albumin concentrations, impaired renal function and coadministration of cyclosporine have been reported to be associated with increased clearance of MPA. The aim of the study was to develop a population pharmacokinetic model describing the relationship between MMF dose and total MPA (tMPA), unbound MPA (fMPA), total MPAG (tMPAG) and unbound MPAG (fMPAG). In this model the correlation between pharmacokinetic parameters and renal function, plasma albumin concentrations and cotreatment with cyclosporine was quantified. tMPA, fMPA, tMPAG and fMPAG concentration–time profiles of renal transplant recipients cotreated with cyclosporine (n = 48) and tacrolimus (n = 45) were analyzed using NONMEM. A 2- and 1-compartment model were used to describe the pharmacokinetics of fMPA and fMPAG. The central compartments of fMPA and fMPAG were connected with an albumin compartment allowing competitive binding (bMPA and bMPAG). tMPA and tMPAG were modeled as the sum of the bound and unbound concentrations. EHC was modeled by transport of fMPAG to a separate gallbladder compartment. This transport was decreased in case of cyclosporine cotreatment (P < 0.001). In the model, clearance of fMPAG decreased when creatinine clearance (CrCL) was reduced (P < 0.001), and albumin concentration was correlated with the maximum number of binding sites available for MPA and MPAG (P < 0.001). In patients with impaired renal function cotreated with cyclosporine the model adequately described that increasing fMPAG concentrations decreased tMPA AUC due to displacement of MPA from its binding sites. The accumulated MPAG could also be reconverted to MPA by the EHC, which caused increased tMPA AUC in patients cotreated with tacrolimus. Changes in CrCL had hardly any effect on fMPA exposure. A decrease in plasma albumin concentration from 0.6 to 0.4 mmol/l resulted in ca. 38% reduction of tMPA AUC, whereas no reduction in fMPA AUC was seen. In conclusion, a pharmacokinetic model has been developed which describes the relationship between dose and both total and free MPA exposure. The model adequately describes the influence of renal function, plasma albumin and cyclosporine co-medication on MPA exposure. Changes in protein binding due to altered renal function or plasma albumin concentrations influence tMPA exposure, whereas fMPA exposure is hardly affected

Toxicokinetics of ibogaine and noribogaine in a patient with prolonged multiple cardiac arrhythmias after ingestion of internet purchased ibogaine

Background: Ibogaine is an agent that has been evaluated as an unapproved anti-addictive agent for the management of drug dependence. Sudden cardiac death has been described to occur secondary to its use. We describe the clinical effects and toxicokinetics of ibogaine and noribogaine in a single patient. For this purpose, we developed a LC-MS/MS-method to measure ibogaine and noribogaine plasma-concentrations. We used two compartments with first order absorption. Case details: The maximum concentration of ibogaine was 1.45 mg/L. Our patient developed markedly prolonged QTc interval of 647ms maximum, several multiple cardiac arrhythmias (i.e., atrial tachycardia and ventricular tachycardia and Torsades des Pointes). QTc-prolongation remained present until 12 days after ingestion, several days after ibogaine plasma-levels were low, implicating clinically relevant noribogaine concentrations long after ibogaine had been cleared from the plasma. The ratio k12/k21 for noribogaine was 21.5 and 4.28 for ibogaine, implicating a lower distribution of noribogaine from the peripheral compartment into the central compartment compared to ibogaine. Conclusions: We demonstrated a linear relationship between the concentration of the metabolite and long duration of action, rather than with parent ibogaine. Therefore, after (prolonged) ibogaine ingestion, clinicians should beware of long-term effects due to its metabolite

Nonlinear Relationship between Mycophenolate Mofetil Dose and Mycophenolic Acid Exposure: Implications for Therapeutic Drug Monitoring

Mycophenolate mofetil (MMF) is an immunosuppressive drug used in renal transplant patients. Upon oral administration it is hydrolyzed to the active agent mycophenolic acid (MPA). In renal transplant recipients, MMF therapy is optimal when the area under the curve of MPA is 30 to 60 mg·h/L. When MMF doses are adjusted, a linear relationship between dose and MPA exposure is assumed. In this study, the linearity of MMF pharmacokinetics was investigated. MPA concentration-time profiles from renal transplant recipients cotreated with cyclosporine (n = 140) or tacrolimus (n = 101) were analyzed retrospectively using nonlinear mixed-effects modeling. The correlation between the MMF dose and the pharmacokinetics parameters was evaluated. In the developed population pharmacokinetics model MPA clearance and the central volume of distribution were correlated with cyclosporine coadministration and time posttransplantation. The pharmacokinetics of MPA were not linear. Bioavailability decreased with increasing MMF doses. Compared with an MMF dose of 1000 mg (=100%), relative bioavailability was 123%, 111%, 94%, and 90% in patients receiving MMF doses of 250, 500, 1500, and 2000 mg in combination with cyclosporine (P <0.001); respective values in tacrolimus-cotreated patients were 176%, 133%, 85%, and 76% (P <0.001). Because of the decreasing relative bioavailability, MPA exposure will increase less than proportionally with increasing MMF doses. MMF exhibits nonlinear pharmacokinetics. This should be taken into account when performing therapeutic drug monitorin

Single-nucleotide polymorphisms in P450 oxidoreductase and peroxisome proliferator-activated receptor-α are associated with the development of new-onset diabetes after transplantation in kidney transplant recipients treated with tacrolimus.

New-onset diabetes after transplantation (NODAT) is an important complication after kidney transplantation. The etiology of the malady is multifactorial and includes both environmental and genetic factors. NODAT is a polygenic disease and many single-nucleotide polymorphisms could constitute potential risk factors. Peroxisome proliferator-activated receptor α (PPARα) and P450 oxidoreductase (POR) play a central role in the control of energy metabolism in humans. Some recent data highlighted a possible functional impact of two single-nucleotide polymorphisms in PPARα (rs4253728 G>A and rs4823613 A>G) and one coding variant in POR (rs1057868; POR*28; A503V) on the activity of their respective encoded proteins. In the present study, we assessed the association between these variants and the risk of developing NODAT after kidney transplantation

The pharmacokinetics and pharmacodynamics of mycophenolate mofetil in younger and elderly renal transplant recipients

Aims: Elderly transplant recipients have a lower incidence of acute rejection, and a higher risk to die from infectious complications. A potential cause may be differences in the pharmacokinetics (PK) or pharmacodynamics (PD) of the immunosuppressive drugs they are taking. This study was designed to comprehensively evaluate the influence of age on the PK and PD of mycophenolic acid (MPA). Methods: In this study the PK and PD of MPA was studied in 26 elderly and 54 younger renal transplant recipients treated with mycophenolate mofetil and tacrolimus. Patients were sampled repetitively, both before and during the first 6 months after kidney transplantation. Age-related variability in MPA PK, baseline IMPDH activity, as well as MPA-induced IMPDH inhibition were studied. Results: The IMPDH activity pre-transplantation did not differ between elderly and younger patients. Neither IMPDH activity pre-transplantation nor maximum IMPDH inhibition was significantly correlated with the patients' age. The area under the MPA plasma concentration–time curve (AUC0–12h) and the area under the effect (IMPDH activity)–time curve (AEC0–12h) from 0 to 12 h were also not significantly different between the two groups. We found no significant differences in EC50 and Emax between elderly and younger patients. Conclusions: Age did not significantly affect the PK or PD of MPA. It is unlikely that the lower incidence of acute rejection in elderly patients, or the higher risk to die from a severe infection in elderly patients is due to different handling of MPA in the elderly