Dysarthria and apraxia of speech associated with FK-506 (tacrolimus)

Evaluation of Tacrolimus' Adverse Effects on Zebrafish in Larval and Adult Stages by Using Multiple Physiological and Behavioral Endpoints

Tacrolimus (FK506) is a common immunosuppressant that is used in organ transplantation. However, despite its importance in medical applications, it is prone to adverse side effects. While some studies have demonstrated its toxicities to humans and various animal models, very few studies have addressed this issue in aquatic organisms, especially zebrafish. Here, we assessed the adverse effects of acute and chronic exposure to tacrolimus in relatively low doses in zebrafish in both larval and adult stages, respectively. Based on the results, although tacrolimus did not cause any cardiotoxicity and respiratory toxicity toward zebrafish larvae, it affected their locomotor activity performance in light-dark locomotion tests. Meanwhile, tacrolimus was also found to slightly affect the behavior performance, shoaling formation, circadian rhythm locomotor activity, and color preference of adult zebrafish in a dose-dependent manner. In addition, alterations in the cognitive performance of the fish were also displayed by the treated fish, indicated by a loss of short-term memory. To help elucidate the toxicity mechanism of tacrolimus, molecular docking was conducted to calculate the strength of the binding interaction between tacrolimus to human FKBP12. The results showed a relatively normal binding affinity, indicating that this interaction might only partly contribute to the observed alterations. Nevertheless, the current research could help clinicians and researchers to further understand the toxicology of tacrolimus, especially to zebrafish, thus highlighting the importance of considering the toxicity of tacrolimus prior to its usage.

Tacrolimus Drug-Drug Interaction with Nirmatrelvir/Ritonavir (Paxlovid™) Managed with Phenytoin

INTRODUCTION

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 or COVID-19) pandemic has had a significant impact on communities and health systems. The Federal Drug Administration (FDA) authorized Pfizer's nirmatrelvir/ritonavir (Paxlovid™) through an EUA for the treatment of mild to moderate cases of COVID-19 at high risk for progression to severe disease. Patients with a history of transplant who test positive for COVID-19 are considered high risk because of their immunosuppression and are therefore candidates for nirmatrelvir/ritonavir.

CASE REPORT

This is a case of a 67-year-old female with a past medical history of orthotopic heart transplant who received tacrolimus as part of her immunosuppressive regimen. She originally presented with complaints of dyspnea and cough for several days in the setting of COVID-19. The patient was started on nirmatrelvir/ritonavir due to her high risk for progression to severe disease. Four days after starting nirmatrelvir/ritonavir, she presented to the ED for slowed speech, fatigue, weakness, and loss of appetite. Upon admission she was found to have a supratherapeutic tacrolimus level of 176.4 ng/mL and an acute kidney injury. In this case, phenytoin was used as a CYP3A4 inducer to quickly decrease the tacrolimus level to within therapeutic range.

CONCLUSION

This case highlights the strong and important drug-drug interaction between tacrolimus and nirmatrelvir/ritonavir leading to toxic levels of tacrolimus. It also demonstrates the utility and effectiveness of phenytoin as a "rescue" medication for tacrolimus toxicity.

Catatonia as a manifestation of tacrolimus-induced neurotoxicity in organ transplant patients: a case series

Tacrolimus has been associated with severe neurotoxicity in organ transplant patients. Catatonia can be a rare manifestation of tacrolimus-induced neurotoxicity as we report two cases of catatonia in solid organ transplant patients on tacrolimus. Catatonic symptoms completely resolved in these patients after reducing the tacrolimus dosage or switching it to alternative immunosuppressants. Catatonia symptoms in organ transplant patients should alert clinicians to look for tacrolimus-induced neurotoxicity despite normal serum tacrolimus levels and neuroimaging findings.

Mutism and persistent dysarthria due to tacrolimus-based immunosuppression following allogeneic liver transplantation

Tacrolimus is a potent immunosuppressant medication with a low therapeutic index. We report a case of mutism with persistent dysarthria in a patient receiving tacrolimus-based immunosuppression following allogeneic liver transplantation. A 59-year-old female patient with end-stage liver disease secondary to primary sclerosing cholangitis underwent successful allogeneic liver transplantation. The patient was started on tacrolimus for prevention of allograft rejection and subsequently developed complete mutism. Following consultation of the medical toxicology service, tacrolimus was discontinued and the patient's mutism gradually improved. However, the patient still has moderate dysarthria more than 2 years after tacrolimus discontinuation. The Naranjo probability scale revealed a probable adverse reaction of mutism and dysarthria associated with tacrolimus therapy. Mutism is an uncommon complication of calcineurin inhibitors. Both cyclosporine and tacrolimus have been associated with mutism, though mutism may be more common in patients treated with tacrolimus. The mechanism of injury has not been delineated, although liver transplant patients and patients with preexisting hepatic encephalopathy or neurologic disease may be at increased risk for this complication. The mainstay of treatment is tacrolimus dose reduction or discontinuation, although benzodiazepine therapy may be beneficial in the treatment of this disorder. Clinicians should be aware of the potential adverse effects associated with calcineurin inhibitor toxicity in transplant patients and should advocate for aggressive and rapid treatment of this serious adverse drug effect.

Neuroimaging and neurologic complications after organ transplantation

Neurologic complications are common after transplantation and affect 30-60% of transplant recipients. The etiology of most of the posttransplant neurologic disorders is related to the opportunistic infections, both systemic and involving central nervous system (CNS), toxicity of immunosuppressive medications, and the metabolic insult created by the underlying primary disease and the transplant procedure. Neuroimaging studies are one of the key tools in the evaluation and enable early diagnosis of neurologic complications in transplant patients, especially posterior reversible leukoencephalopathy syndrome, central pontine myelinolysis, intracerebral hemorrhage, and fungal and bacterial abscesses. Magnetic resonance imaging (MRI) is the preferred technique, but each of the available neuroimaging techniques offers a unique insight into the pathophysiologic mechanisms underlying neurologic complications of transplantation. The role of neuroimaging in this population includes early detection of calcineurin inhibitor neurotoxicity, opportunistic infections, neoplasia, metabolic disorders, or cerebrovascular diseases. In addition, we can monitor longitudinal progression of disease and treatment response.

Neuropsychiatric complications after liver transplantation: role of immunosuppression and hepatitis C

Neuropsychiatric complications are an important source of morbidity following orthotopic liver transplantation. Etiology of liver disease and type of immunosuppression are possible related factors. The aim of this study was to describe the prevalence of neuropsychiatric complications after liver transplantation, the role of immunosuppression, and the association between these and specific liver diseases such as hepatitis C. One hundred twenty-eight patients with liver transplants were studied. Tacrolimus was the primary immunosuppressant in 101 patients and cyclosporine in 27 patients. Seventy-five complications in 49 patients (38.2%) were reported. In 43 patients, the etiology was associated with immunosuppression: 36 on tacrolimus and 7 on cyclosporine (P = 0.34). Seventeen and four-tenths percent of patients with hepatitis C and 4.6% of patients without hepatitis C developed depression (P = 0.02). There is no difference between types of primary immunosuppression and neuropsychiatric complications. There is a significantly greater incidence of depression in patients transplanted for hepatitis C.

Tacrolimus (FK506)-induced mutism after liver transplant

Tacrolimus (FK506), an immunosuppressant, has been associated with mutism in adults after liver transplant. Speech arrest, agitation, tremor, ataxia, and downward gaze deviation in a 5-year-old female 13 days after orthotopic liver transplant are reported. FK506, which began to be administered 12 days earlier, rose to a level of 44 ng/mL (normal range, 10-20 ng/mL) 1 day before neurologic abnormalities began. FK506 dose level was maintained and then reduced. Three days later the patient could say a few single words and extra-ocular movement returned to normal. Four months later, she continued to exhibit decreased fluency and dysarthria with ataxia. One year later, decreased fluency and mild ataxia persists. Rapid identification of speech loss linked to FK506 may be important because reduction or cessation of the drug may be associated with reverse of speech loss.

Factors affecting the pharmacokinetics of tacrolimus (FK506) in hematopoietic cell transplant (HCT) patients

Tacrolimus is an immunosuppressant commonly used in the prevention of graft-versus-host disease (GVHD) following allogeneic HCT. Unfortunately, the use of tacrolimus is associated with variable immunosuppression and toxicity. The purpose of this study was to describe tacrolimus population pharmacokinetic parameters, to identify relationships between clinical covariates and pharmacokinetic estimates, and to develop a model to predict tacrolimus clearance in HCT patients. Steady-state whole blood tacrolimus concentrations (n = 1625) obtained during intravenous and oral therapy were analyzed in 122 patients. Population clearance (CL) was 5.22 l/h and bioavailability (F) was 0.28. The influence of clinical covariates on population estimates of CL and F of tacrolimus were tested with nonlinear mixed effects models (NONMEM). CL was significantly reduced by elevations in total bilirubin 2.0-9.9 mg/dl (CL * 0.797), bilirubin > or = 10 mg/dl (CL * 0.581), serum creatinine > or = 2 mg/dl (CL * 0.587), grade III/IV graft-versus-host disease (CL * 0.814) and veno-occlusive disease (CL 0.814). No covariates were predictive of oral F. The interindividual variabilities in CL and F were 33% and 44%, respectively. Residual variability was 27.5% and 16.8% at tacrolimus concentrations of 10 microg/l and 20 microg/l, respectively. These models may be used to predict tacrolimus clearance and doses in adult patients following HCT.

Tacrolimus-associated mutism after orthotopic liver transplantation

BACKGROUND

Mutism/speech apraxia has been well documented as a toxic effect of cyclosporine after liver transplantation but has been reported only rarely with tacrolimus. Brain imaging with magnetic resonance or computed tomography has failed to demonstrate abnormalities in affected patients.

METHODS

We present the first example of an acute onset of loss of speech associated with a sudden elevation of serum tacrolimus level after successful orthotopic liver transplantation. We also describe the positron emission tomography (PET) scan of this patient's brain.

RESULTS

PET scan imaging of the brain was abnormal, demonstrating decreased metabolism in the posterior temporo-parieto-occipital regions. Statistical probability mapping revealed additional areas of hypometabolism in the cingulate gyrus.

CONCLUSIONS

PET scan revealed abnormalities of the brain in a patient with tacrolimus-induced mutism. The cingulate gyrus may play a role in the mutism/speech apraxia syndrome seen with cyclosporine/tacrolimus neurotoxicity.

Long-term care of the liver transplant recipient

Many liver transplant recipients are now reaching survival beyond 5 years from the liver transplant procedure, and many others are alive more than a decade from acquiring their new liver. Orthotopic liver transplant recipients enjoy the benefits of normal liver function, but a variety of metabolic and other medical problems often develop that require diagnosis and adequate management. These problems include hyperlipidemia, obesity, diabetes mellitus, renal disfunction, arterial hypertension, bone disease and neuropsychiatric syndromes. The gastroenterologist, internist, or local family physician is frequently called on to identify and treat these postoperative complications in conjunction with physicians at the transplant center.