Drug-drug interaction comparison between tacrolimus and phenobarbital in different formulations for paediatrics and adults

To compare drug-drug interaction (DDI) between tacrolimus and different formulations of phenobarbital in paediatrics and adults.Physiologically based pharmacokinetics (PBPK) models were used to evaluate DDI between phenobarbital (oral (p.o.) and intravenous (i.v.) formulations) and tacrolimus in paediatrics and adults. All dosing regimens were maintained for 7 days.Compared to i.v. phenobarbital, p.o. phenobarbital could decrease pharmacokinetic (PK) parameters of tacrolimus much more in both paediatrics and adults. On day 7, the results showed that the ratio of C_max for tacrolimus in the presence and absence of phenobarbital were 0.13 (p.o.) and 0.48 (i.v.), respectively, in paediatrics, while 0.54 (p.o.) and 0.73 (i.v.) in adults, respectively. The ratios of the area under the concentration-time curve (AUC) were 0.06 (p.o.) and 0.18 (i.v.) in paediatrics, while 0.46 (p.o.) and 0.53 (i.v.) in adults, respectively. PK parameters of tacrolimus decreased more significantly in paediatrics compared to adults.In paediatric, phenobarbital had a greater impact on PK of tacrolimus than that in adults. P.o. phenobarbital reduced PK parameters of tacrolimus even more than i.v. administration. In clinical practice, the concentration monitoring and dosage adjustment of tacrolimus should be emphasised when co-administrated with phenobarbital, especially in paediatric or in p.o. formulation.Key pointsThe results indicated that p.o. and i.v. phenobarbital both had a significant DDI with tacrolimus in paediatrics and adults.Phenobarbital had a greater impact on the PK of tacrolimus over time in paediatrics.P.o. administration of phenobarbital can reduce the PK parameters of tacrolimus more.

Predictors of tacrolimus pharmacokinetic variability: current evidences and future perspectives

INTRODUCTION

In kidney transplantation, tacrolimus (TAC) is at the cornerstone of current immunosuppressive strategies. Though because of its narrow therapeutic index, it is critical to ensure that TAC levels are maintained within this sharp window through reactive adjustments. This would allow maximizing efficiency while limiting drug-associated toxicity. However, TAC high intra- and inter-patient pharmacokinetic (PK) variability makes it more laborious to accurately predict the appropriate dosage required for a given patient.

AREAS COVERED

This review summarizes the state-of-the-art knowledge regarding drug interactions, demographic and pharmacogenetics factors as predictors of TAC PK. We provide a scoring index for each association to grade its relevance and we present practical recommendations, when possible for clinical practice.

EXPERT OPINION

The management of TAC concentration in transplanted kidney patients is as critical as it is challenging. Recommendations based on rigorous scientific evidences are lacking as knowledge of potential predictors remains limited outside of DDIs. Awareness of these limitations should pave the way for studies looking at demographic and pharmacogenetic factors as well as gut microbiota composition in order to promote tailored treatment plans. Therapeutic approaches considering patients' clinical singularities may help allowing to maintain appropriate concentration of TAC.

Effects of Different Tacrolimus Doses on Adipose-Derived Stem Cells

OBJECTIVES

Tacrolimus is currently one of the most commonly used immunosuppressant agents to prevent rejection in organ transplant. Although modern immunosuppressive agents have been successful, rejection cannot be completely prevented. Therefore, in organ transplant research, additional treatment methods are being investigated, with the most important one being stem cell therapy. In addition to tacrolimus therapy, stem cell therapy is now clinically applicable, with frequency of concomitant use seeming to expand in the future. In this study, the effects of tacrolimus on stem cells were investigated.

MATERIALS AND METHODS

Adipose-derived stem cells were treated with tacrolimus at different doses and time points. We analyzed the effects of changes in stem cell proliferation using MTT analysis. Sox2, Oct3/4, and Nanog protein levels were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to measure stem cell pluripotency capabilities.

RESULTS

Our observations showed that tacrolimus causes changes in stem cell proliferation and pluripotency, with changes dependent on time and dose.

CONCLUSIONS

The dose of tacrolimus and the time of application of stem cells are important in the planning of stem cell therapy in organ transplant.

Drug interaction between dabrafenib and immunosuppressive drugs: about one case

Melanoma is a major public health problem. In recent years, it has been shown that melanoma can be characterized by specific oncogenes mutations such as the BRAF mutation, leading to the development of new therapeutic drugs. Dabrafenib is an inhibitor of BRAF, approved as a first-line treatment of metastatic or unresectable stage 3 or 4 melanoma with the BRAF mutation. Few studies have evaluated the drug interaction potential of dabrafenib. This molecule is an enzyme inducer that increases the synthesis of drug-metabolizing enzymes, including CYP3A4, CYP2B6, CYP2C8, CYP2C9, CYP2C19, and UGT enzymes. Accordingly, the plasma concentrations of drugs metabolized by these enzymes are decreased. The decrease in plasma concentrations may cause a reduction or even loss of the clinical effect of these drugs. Many drugs metabolized by these enzymes may be affected, especially midazolam, warfarin, or rifampicin. However, interactions with immunosuppressants have not been described. Everolimus and tacrolimus are two immunosuppressive drugs metabolized by CYP3A4. We report a case of drug interaction between dabrafenib and immunosuppressive drugs (everolimus, tacrolimus), observed in a transplanted heart patient, requiring dosage adjustment of its immunosuppressive treatment to avoid graft rejection.

Case report: boldo (Peumus boldus) and tacrolimus interaction in a renal transplant patient

INTRODUCTION

Boldo is an extract of a Chilean tree leave (Peumus boldus mol) that have been traditionally employed in folk medicine. We have presented a case of subtherapeutic tacrolimus levels in a renal transplant patient while taking boldo. In the literature search, no interaction has been reported between boldo and tacrolimus.

CASE REPORT

A 78-year-old Hispanic man with history of diabetes mellitus, hypertension, and deceased donor renal transplant in 2005 presented to the renal clinic for regular follow-up on September 1, 2010. No complaints were reported and physical examination was unremarkable. Laboratory tests taken on July 26, 2010, were significant for tacrolimus level of <3 ng/mL (measured by liquid chromatography/tandem mass spectrometry) and serum creatinine of 1.2 mg/dL (106 μmol/L). Medications included tacrolimus 2 mg bid and mycophenolate 500 mg bid. On further inquiry, the patient admitted taking herbal medication, boldo 300 mg bid, for the last few weeks. There was no change in his regular medications. He was adherent to his medication. He had been taking tacrolimus from the same company and pharmacy since August 2009. The last dose of boldo was on September 1, 2010. One week after he stopped taking boldo, tacrolimus level was 6.1 ng/mL (9/8/2010) on the same tacrolimus dose of 2 mg bid. Tacrolimus dose was increased to 3 mg bid (9/9/2010), awaiting tacrolimus levels. Subsequent levels (ng/mL) were 8.6 and 9.5, which made us resume the prior tacrolimus dose (2 mg bid).

CONCLUSIONS

We have reported a case of an allograft renal transplant recipient who presented to the clinic with subtherapeutic levels of tacrolimus while taking the herbal remedy boldo. Tacrolimus levels rose to the intended target after discontinuation of boldo. Although it is a single case report, our observation suggests a possible herb-drug interaction.