Tacrolimus Toxicity Associated with Concomitant Metoclopramide Therapy

Tacrolimus-Induced Neurotoxicity After Transplant: A Literature Review

Tacrolimus, a calcineurin inhibitor, is an immunosuppressant used globally to prevent rejection after organ transplantation. Although it significantly improves outcomes for solid organ transplant patients, it is associated with various side effects such as nephrotoxicity and neurotoxicity. Tacrolimus-induced neurotoxicity is frequently encountered in clinical practice and can present with a variety of symptoms that may occur even at therapeutic levels. Although tacrolimus-induced neurotoxicity is well documented, there is limited literature available on pharmacologic management. Twenty-eight case reports of tacrolimus-induced neurotoxicity were identified and analyzed in addition to other literature including reviews, retrospective studies, and animal model studies. The severity of cases of tacrolimus-induced neurotoxicity reported ranged from mild symptoms that could be managed with symptomatic treatment to conditions such as posterior reversible encephalopathy syndrome and chronic inflammatory demyelinating polyradiculoneuropathy that may require more immediate intervention. This information was utilized in addition to clinical experience to compile potential management options for prevention and treatment of neurotoxic adverse events. This review is limited by the utilization of primarily retrospective studies and case reports. The available literature on the subject is largely narrative and there are no guidelines on treatment of tacrolimus-induced neurotoxicity at the time of this research. This comprehensive review may guide further studies to investigate the pathophysiology of tacrolimus-induced neurotoxicity and to define patient-specific strategies for mitigation or minimization of neurotoxicity. This is especially important given that management of tacrolimus-induced neurotoxicity can include changes to immunosuppression that can result in an increased risk of rejection.

Immunosuppressive drugs and the gastrointestinal tract in renal transplant patients

Gastrointestinal (GI) discomfort is common after renal transplantation and can be caused by the use of various immunosuppressive drugs. GI symptoms affect the quality of life, lead to an impaired graft survival and an increased mortality. Moreover, diseases and disturbances of the GI tract also affect the pharmacokinetics of immunosuppressive drugs. This review addresses the interaction between immunosuppressive agents and GI disorders. The GI tract is involved in the metabolism of several immunosuppressive drugs. Calcineurin inhibitors, mTor inhibitors, and corticosteroids are subjected to metabolism by the intestinal cytochrome P450 (CYP3A) and by the drug efflux pump ABCB1. Mycophenolate is partly metabolized in the stomach and intestine and undergoes enterohepatic recirculation. Gastrointestinal disturbances can lead to a modified exposure to immunosuppressive drugs. In the first and second part of this review, we focus on the role of the GI tract in the pharmacokinetics of the immunosuppressive drugs and how to adjust immunosuppressive therapy in patients with vomiting, need for tube feeding, delayed gastric emptying, intestinal resection, and diarrhea. In the third part, we review the GI adverse effects of the various immunosuppressive drugs, with special attention for diarrhea and dyspepsia. Finally, we discuss the effects of drugs used for relief of GI complaints on the exposure to immunosuppressive agents.

Expression of clinically relevant drug-metabolizing enzymes along the human intestine and their correlation to drug transporters and nuclear receptors: An intra-subject analysis

The oral bioavailability of many drugs is highly influenced not only by hepatic but also by intestinal biotransformation. To estimate the impact of intestinal phase I and II metabolism on oral drug absorption, knowledge on the expression levels of the respective enzymes is an essential prerequisite. In addition, the potential interplay of metabolism and transport contributes to drug disposition. Both mechanisms may be subjected to coordinative regulation by nuclear receptors, leading to unwanted drug-drug interactions due to induction of intestinal metabolism and transport. Thus, it was the aim of this study to comprehensively analyse the regional expression of clinically relevant phase I and II enzymes along the entire human intestine and to correlate these data to expression data of drug transporters and nuclear receptors of pharmacokinetic relevance. Gene expression of 11 drug-metabolizing enzymes (CYP2B6, 2C8, 2C9, 2C19, 2D6, 3A4, 3A5, SULT1A, UGT1A, UGT2B7, UGT2B15) was studied in duodenum, jejunum, ileum and colon from six organ donors by real-time RT-PCR. Enzyme expression was correlated with expression data of the nuclear receptors PXR, CAR and FXR as well as drug transporters observed in the same cohort. Intestinal expression of all studied metabolizing enzymes was significantly higher in the small intestine compared to colonic tissue. CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP3A4/5, SULT1A, UGT1A and UGT2B7 expression increased from the duodenum to jejunum but was markedly lower in the ileum. In the small intestine, that is, the predominant site of drug absorption, the highest expression has been observed for CYP3A4, CYP2C9, SULT1A and UGT1A. In addition, significant correlations were found between several enzymes and PXR as well as ABC transporters in the small intestine. In conclusion, the observed substantial site-dependent intestinal expression of several enzymes may explain regional differences in intestinal drug absorption. The detected correlations between intestinal enzymes, transporters and nuclear receptors provide indirect evidence for their coordinative expression, regulation and function in the human small intestine.

MSBIS: A Multi-Step Biomedical Informatics Screening Approach for Identifying Medications that Mitigate the Risks of Metoclopramide-Induced Tardive Dyskinesia

In 2009 the U.S. Food and Drug Administration (FDA) placed a black box warning on metoclopramide (MCP) due to the increased risks and prevalence of tardive dyskinesia (TD). In this study, we developed a multi-step biomedical informatics screening (MSBIS) approach leveraging publicly available bioactivity and drug safety data to identify concomitant drugs that mitigate the risks of MCP-induced TD. MSBIS includes (1) TargetSearch (http://dxulab.org/software) bioinformatics scoring for drug anticholinergic activity using CHEMBL bioactivity data; (2) unadjusted odds ratio (UOR) scoring for indications of TD-mitigating effects using the FDA Adverse Event Reporting System (FAERS); (3) adjusted odds ratio (AOR) re-scoring by removing the effect of cofounding factors (age, gender, reporting year); (4) logistic regression (LR) coefficient scoring for confirming the best TD-mitigating drug candidates. Drugs with increasing TD protective potential and statistical significance were obtained at each screening step. Fentanyl is identified as the most promising drug against MCP-induced TD (coefficient: −2.68; p-value < 0.01). The discovery is supported by clinical reports that patients fully recovered from MCP-induced TD after fentanyl-induced general anesthesia. Loperamide is identified as a potent mitigating drug against a broader range of drug-induced movement disorders through pharmacokinetic modifications. Using drug-induced TD as an example, we demonstrated that MSBIS is an efficient in silico tool for unknown drug-drug interaction detection, drug repurposing, and combination therapy design.

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An in silico MSBIS approach was developed to identify concomitant drugs that mitigate the side effects of a primary drug.

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Fentanyl and loperamide were identified to protect patients against drug-induced tardive dyskinesia (TD).

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MSBIS can be generalized to provide rational starting points for drug repurposing and combination therapy design.

Many dopamine antagonists cause TD and other severe, irreversible movement disorders. 120 drugs were screened using the MSBIS approach, leading to the discovery of fentanyl and loperamide. When co-administered with dopamine antagonists such as metoclopramide, they may protect patients against drug-induced movement disorders including TD. Their mechanisms of toxicity-mitigating action are remarkably different. The statistical significance of the findings was established using the FDA Adverse Event Reporting System and supported by published clinical reports and pharmacologic data. This study demonstrated the feasibility of the MSBIS approach and its applicability in identifying unknown drug-drug interactions that either mitigate undesirable toxicities or synergize therapeutic effects.

Neurologic complications of transplantation

Major neurologic morbidity, such as seizures and encephalopathy, complicates 20-30% of organ and stem cell transplantation procedures. The majority of these disorders occur in the early posttransplant period, but recipients remain at risk for opportunistic infections and other nervous system disorders for many years. These long-term risks may be increasing as acute survival increases, and a greater number of "sicker" patients are exposed to long-term immunosuppression. Drug neurotoxicity accounts for a significant proportion of complications, with posterior reversible leukoencephalopathy syndrome, primarily associated with calcineurin inhibitors (i.e., cyclosporine and tacrolimus), being prominent as a cause of seizures and neurologic deficits. A thorough evaluation of any patient who develops neurologic symptoms after transplantation is mandatory, since reversible and treatable conditions could be found, and important prognostic information can be obtained.

Tripterygium wilfordii hook f increase the blood concentration of tacrolimus

OBJECTIVE

To observe the influence of the Tripterygium wilfordii Hook F (T II) on the blood concentration of tacrolimus and analyze the impact of this effect.

METHOD

Twenty-two renal transplant receipts taking tacrolimus combined with the T II were selected for this study. We analyzed the blood concentrations and the rate of concentration compared with dosage (C/D rate) pre- and postcombination over 6 months. All cases underwent the CYP3A5 genotype test.

RESULT

The concentrations of tacrolimus were raised to a certain degree after the combination in all the cases. The first-time elevation differed from 1 week to 4 months. The C/D rate increased by 1.7 to 7.2 times with most evaluated C/D rates ranging from 1.8 to 3.8. The elevated C/D rate of the subgroup of CYP3A5 1/1 and 1/3 (n = 10) contrasted with the 3/3 genotype subgroup (n = 12: 2.99 +/- 1.71 vs 2.55 +/- 1.07; P = .472). The mycophenolate mofetil subgroup (n = 17) was not contrasted to the mizoribine subgroup (n = 5: 2.85 +/- 1.51 vs 2.31 +/- 0.26; P = .498).

CONCLUSION

T II considerably increased the blood concentration and the C/D rate of tacrolimus. The degree of increase was probably not related to the CYP3A5 genotype and the combination of immunosuppressive agents.

Tacrolimus in Diabetic Kidney Transplant Recipients: Pharmacokinetics and Application of a Limited Sampling Strategy

The effect of diabetes mellitus on the pharmacokinetics of tacrolimus is not well characterized. We have compared tacrolimus 12-hour steady-state concentration-time profiles in diabetic (n = 11) and demographically matched nondiabetic (n = 9) stable kidney transplant recipients and derived a limited sampling strategy for the estimation of tacrolimus area under the concentration-time curve (AUC(0-12)). Tacrolimus concentration was measured by liquid chromatography tandem mass spectrometry and acetaminophen absorption method was used to characterize gastric emptying time. Demographic and biochemical characteristics were comparable between the two groups with the exception of significantly higher glycated hemoglobin levels in patients with diabetes (P = 0.02). Time to maximum concentration (T(max)) of acetaminophen was significantly longer in diabetics [D: 74.1 minute versus nondiabetics (ND): 29.3 minutes, P = 0.02]; however, tacrolimus T(max) was not significantly different (D: 121 minutes versus ND: 87 minutes, P = 0.15). Median (interquartile range) of tacrolimus AUC(0-12) was 114 (101-161) microg*hr/L in patients with diabetes and 113 (87-189) microg*hr/L in nondiabetics (P = 0.62). The following limited sampling equation [AUC(pred) (microg*hr/L) = 18.70 - 1.72 C(1 hr) - 4.09 C(2 hr) + 14.40 C(3 hr)] was derived from a training data set that included 10 patients. The correlation coefficient between model-predicted and observed AUC0-12 values was 0.999. Mean prediction error and root mean square error of the model-predicted values derived from the patients in validation data set were 0.04 and 17.48 microg*hr/L, respectively. In conclusion, it appears that diabetes has a modest effect on the rate but not the extent of tacrolimus absorption, and a three-point abbreviated sampling strategy common to both groups may prove useful for the estimation of tacrolimus exposure in kidney transplant recipients.

Tacrolimus Intoxication Resolved by Gastrointestinal Bleeding: Case Report

Tacrolimus is a potent immunosuppressive agent widely used in renal and liver transplantations. Its potential side effects due to overdosing are variable. Most commonly toxic tacrolimus blood levels affect the central and peripheral nervous systems. Once absorbed, tacrolimus binds to plasma proteins and accumulates within erythrocytes. Current treatment strategies to overcome acute intoxications focus on the induction of hepatic cytochrome P450 enzymes to accelerate tacrolimus degradation. We report the case of a 69-year-old renal transplant recipient presenting with acute liver failure, septic shock, and tacrolimus intoxication. The intoxication was resolved by massive gastrointestinal bleeding and subsequent transfusion of packed erythrocytes. We concluded that exchange blood transfusions offer an alternative therapeutic approach for patients with severe liver function impairment and tacrolimus intoxication.

Pharmacokinetics and interactions of headache medications, part I: introduction, pharmacokinetics, metabolism and acute treatments

Recent progress in the treatment of primary headaches has made available specific, effective and safe medications for these disorders, which are widely spread among the general population. One of the negative consequences of this undoubtedly positive progress is the risk of drug-drug interactions. This review is the first in a two-part series on pharmacokinetic drug-drug interactions of headache medications. Part I addresses acute treatments. Part II focuses on prophylactic treatments. The overall aim of this series is to increase the awareness of physicians, either primary care providers or specialists, regarding this topic. Pharmacokinetic drug-drug interactions of major severity involving acute medications are a minority among those reported in literature. The main drug combinations to avoid are: i) NSAIDs plus drugs with a narrow therapeutic range (i.e., digoxin, methotrexate, etc.); ii) sumatriptan, rizatriptan or zolmitriptan plus monoamine oxidase inhibitors; iii) substrates and inhibitors of CYP2D6 (i.e., chlorpromazine, metoclopramide, etc.) and -3A4 (i.e., ergot derivatives, eletriptan, etc.), as well as other substrates or inhibitors of the same CYP isoenzymes. The risk of having clinically significant pharmacokinetic drug-drug interactions seems to be limited in patients with low frequency headaches, but could be higher in chronic headache sufferers with medication overuse.

EFNS guidelines on management of neurological problems in liver transplantation

Neurological impairment after orthotopic liver transplantation (OLT) is common and represents a major source of morbidity and mortality. The diagnosis and management of neurological problems occurring after OLT are difficult and evidence-based guidelines for this task are currently lacking. A Task Force was set up under the auspices of the European Federation of Neurological Societies to devise guidelines to prevent and manage neurological problems in OLT. We selected six major neurological problems and approached them combining an evidence-based scientific literature analysis with a search of consensus by means of a Delphi process. Search results were translated into a series of recommendations constituting a basis for better care of patients with neurological complications after OLT.

Intrapyloric injection of botulinum toxin a for the treatment of persistent gastroparesis following successful pancreas transplantation

Intrapyloric injection of botulinum toxin A (BoTx) successfully improved symptoms in idiopathic and diabetic gastroparesis (DGP) refractory to medical treatment. Therefore, we used it in three pancreas transplant patients done in our institution during the last 18 months. They had severe, persistent DGP despite successful pancreas transplantation. They received 100 units of BoTx during the first injection. The clinical effect became evident within 2 weeks after the treatment, and lasted for an average of 29 weeks (range 14-44 weeks). The patients' subjective evaluation showed improvement of their symptoms and quality of life following BoTx. Patients 2 and 3 had recurrent symptoms at 44 and 24 weeks, respectively, after the first injection; they required a second dose of 90 and 80 units, respectively. They are doing well at 3 months follow-up. Intrapyloric injection of BoTx is safe and efficient. It should be considered for treating residual DGP following successful pancreas transplantation.