Overdose of Tacrolimus as the Trigger Causing Progression of Posterior Reversible Encephalopathy Syndrome and Subsequent Hepatic Infarction After Liver Transplant: A Case Report.

Posterior reversible encephalopathy syndrome is a neurotoxic state accompanied by unique brain imaging patterns and neurologic abnormalities, typically associated with several complex clinical conditions such as preeclampsia/eclampsia, solid-organ transplant procedures, autoimmune diseases, and immunosuppressive agents. The detailed mechanism of posterior reversible encephalopathy syndrome is not known, and the current therapy is only supportive care. Here, we present a 33-year-old parturient woman with preeclampsia complicated with hemolysis, elevated liver enzymes, and low platelet syndrome, fulminant hepatitis B, acute fatty liver, and posterior reversible encephalopathy syndrome. The patient developed gross hepatic infarction soon after liver transplant. After several possible causes were excluded, we found that progression of underlying posterior reversible encephalopathy syndrome-induced endothelial damage by overdose of tacrolimus may have been the major cause for deteriorating hypoperfusion of the transplanted liver and fatal graft failure. In liver transplant recipients, severe posttransplant hypoperfusion of the grafted liver may result in loss of the liver allograft and even mortality. Poor control of underlying posterior reversible encephalopathy syndrome-associated endothelial damage because of tacrolimus overdose may lead to severe hypoperfusion of grafted hepatic vessels and subsequent hepatic infarction. This report highlights tacrolimus as a potential trigger of posterior reversible encephalopathy syndrome and may inform clinical decisions regarding tacrolimus administration in liver transplant recipients with preexisting or newly developed posterior reversible encephalopathy syndrome.

Comparison of Tacrolimus Starting Doses Based on CYP3A5 Phenotype or Genotype in Kidney Transplant Recipients.

BACKGROUND: Selection of expected phenotypes (ie, expressers/non-expressers) is currently used in CYP3A5*3 genotype-based tacrolimus dosing. The authors assessed whether a dosing regimen based on the 3 CYP3A5 genotypes may reduce the occurrence of inadequate exposure. METHODS: Tacrolimus whole blood trough levels (C0) were retrieved from a retrospective cohort of 100 kidney transplant recipients treated with a starting dose of 0.15 (non-expressers) or 0.30 (expressers) mg/kg/d. The authors evaluated the occurrence of overexposures (12 < C0 < 20 ng/mL) or toxic concentrations (C0 ≥ 20 ng/mL). These results were used to set up a new strategy based on the 3 distinct CYP3A5 genotypes, which relevance was evaluated in a prospective cohort of 107 patients. RESULTS: In the retrospective cohort, non-expressers exhibited frequent overexposure (63.6%) or toxic C0 (20.8%). Among expressers, none of the homozygous *1 carriers exhibited overexposure contrary to 25% of the heterozygotes. Based on these results, new tacrolimus starting doses were set at 0.10, 0.20, and 0.30 mg/kg/d for CYP3A5*3/*3, CYP3A5*1/*3, and CYP3A5*1/*1 genotypes, respectively. Tacrolimus overexposure was reduced in the CYP3A5*3/*3 group (63.6% vs 40%, P = .0038). None of the heterozygous patients exhibited toxic tacrolimus C0. Clinical outcomes were not different between the 2 periods, whatever the genotype. Our results indicate that the best tacrolimus exposure was obtained for doses of 0.10, 0.20, and 0.20 mg/kg/d for CYP3A5*3/3, CYP3A5*1/*3, and CYP3A5*1/*1, respectively. CONCLUSIONS: Our results confirm that selecting tacrolimus dosing regimen according to the expected phenotype is appropriate, but that lower than currently recommended doses may be preferable.

Acute calcineurin inhibitor overdose: analysis of cases reported to a national poison center between 1995 and 2011.

Transplant recipients and other patients requiring immunosuppression with calcineurin inhibitors or their household contacts may be exposed to overdose. This study investigated the circumstances, pharmacokinetics and outcomes of overdose with cyclosporine and tacrolimus reported to the Swiss Toxicological Information Centre between 1995 and 2011. Of 145,396 reports by healthcare professionals, 28 (0.02%) concerned enteral or parenteral overdose with these calcineurin inhibitors. Thirteen (46%) were iatrogenic errors, 12 (43%) were with suicidal intent and 3 (11%) were accidental. Iatrogenic overdoses usually involved noncapsule drug formulations. Acute enteral overdoses caused symptoms in a dose-dependent fashion but were generally well tolerated; the mean multiple of patient's usual dose was 20.8 ± 28.8 for symptomatic versus 4.4 ± 3.4 for asymptomatic cases (p = 0.037). The most common symptoms were nausea, headache, somnolence, confusion, hypertension and renal impairment. In contrast, acute intravenous overdoses were often poorly tolerated and resulted in one fatality due to cerebral edema after a cyclosporine overdose. Enteral decontamination measures were performed in six cases involving oral ingestion and appeared to reduce drug absorption, as shown by pharmacokinetic calculations. In the one case where it was used, pharmacoenhancement appeared to accelerate tacrolimus clearance after intravenous overdose.

Acute tacrolimus toxicity in a non-transplant patient.

INTRODUCTION: Tacrolimus is an immunosuppressant widely used in recipients of solid organ transplants to prevent rejection. Toxicity is usually reported in transplant patients. We report the first case of tacrolimus toxicity in a non-transplant patient. CASE REPORT: A 42 year-old, 48 kg woman complained of neck pain following a motor vehicle collision and was admitted for observation. On examination, her pulse was 112 beats/minute and her blood pressure 188/134 mmHg. Because the hypertension and tachycardia might be ethanol withdrawal, she was admitted and treated with multivitamins, folate, and thiamine in her maintenance fluids. She was discharged after 4 days in hospital. The day after her discharge, she was asked to return after it was discovered that she had inadvertently received tacrolimus (total of 400 mg) instead of thiamine. She was admitted with non-oliguric renal failure and metabolic acidosis. A tacrolimus concentration 27 hours after her last exposure was 96.8 ng/mL (therapeutic 5 to 20 ng/mL). Treatment was supportive and she was discharged after 4 days without sequellae. DISCUSSION: Our patient's tacrolimus dose was 2.1 mg/kg/day for 4 days (therapeutic 0.03 to 0.05 mg/kg/day). Her tacrolimus elimination half-life was 16.5 hours, compared to a mean half-life in healthy volunteers of 34.2 +/- 7.7 hours. CONCLUSION: Clinical toxicity, similar to that seen in transplant patients, can develop in non-transplant patients following intravenous administration of supra-therapeutic doses of tacrolimus.

Acute suicidal intoxication with tacrolimus in a kidney transplant patient.

A case of a 23-year-old female, after renal transplant, who had tried to commit suicide with 100 mg of Prograf was described. In the presented case despite the relatively high tacrolimus blood concentration level (>30 microg/l) only severe 5-hour lasting headache and short-term mild hyperglycaemia (7.22 mmol/l), hyperkalemia (5.4 mmol/l) and considerable leukocytosis (19.52 x 10(3)) were observed. In this case there was mild clinical course of intoxication despite tacrolimus high blood concentration. It could not be excluded that early administration of gastric lavage and activated carbon was partly responsible for mild course of poisoning.

Severe prolonged tacrolimus overdose with minimal consequences.

A 59-year-old man inadvertently received a 10-fold increase in his twice-daily oral dose of tacrolimus 1 mg that resulted in trough blood levels above 90 ng/ml for over a week. The patient had end-stage renal disease secondary to diabetes mellitus and had received a kidney transplant from his daughter 3 months earlier. Despite the numerous adverse effects commonly reported with tacrolimus, such as mild nephrotoxicity, nausea, tremors, and elevated liver enzyme levels, our patient's acute but prolonged overdose resulted in minimal signs and symptoms of toxicity. Nevertheless, education regarding the importance of accurate dosing, close monitoring, potential drug interactions, and the various capsule colors should be provided to all patients who receive tacrolimus, as well as their physicians, nurses, and pharmacists, in order to prevent as many errors as possible.

Conversion to neoral for neurotoxicity after primary adult liver transplantation under tacrolimus.

BACKGROUND: Neurological complications after orthotopic liver transplantation (OLTX) have remained a major concern in a small proportion of patients. The etiology of these complications is often thought to be multifactorial: the influence of calcineurin inhibitors is occasionally thought to play an important role. When neurotoxicity occurs after OLTX under tacrolimus, it is usually a minor complication and responds readily to a reduction in the dosage of or a temporary withdrawal of tacrolimus. However, neurotoxic complications occasionally do not respond to this conventional process. Neoral is a microemulsion formulation of cyclosporine. It has more consistent pharmacokinetic parameters and improved bioavailability when compared with conventional cyclosporine. The aim of the present report was to evaluate the role of Neoral in OLTX recipients with neurotoxic complication who failed to respond to a reduction in the dosage of tacrolimus. METHOD: Between August 1995 and November 1997, 330 adults (age >18 years) received primary OLTX under tacrolimus-based immunosuppression (mean age 52.6+/-11.4 years). There were 190 men and 140 women. Twenty-three (7%) patients (mean age 53.2+/-11.8 years; 17 men, 6 women) were converted to Neoral (mean 35+/-41 days after OLTX). These patients were followed until June 1998 (mean follow-up 22.7+/-7.8 months). RESULTS: Four (17.4%) patients died during the follow-up period, and two patients underwent retransplantation. Neurological symptoms improved in all patients who survived. Adequate trough concentrations were achieved in all patients with p.o. Neoral. Nine (39%) patients experienced rejection episodes after conversion. Six (26.1%) patients were converted back to tacrolimus because of ongoing rejection (n=3), retransplantation (n=2), or persistent nausea and vomiting (n=1) without recurrence of the original neurological complication. CONCLUSION: Neurological complications after OLTX disorders that occur under tacrolimus and that fail to respond to a reduction in the dosage can be treated safely by conversion to Neoral. However, the rate of rejection is up to 39%, and patients can often be converted back to tacrolimus without recurrence of the original neurological complication.

Hypothyroidism as a cause of tacrolimus intoxication and acute renal failure: a case report.

The nephrotoxic side effects of cyclophilin-binding agents like cyclosporine A and tacrolimus are well characterized. In severe cases nephrotoxicity may profoundly deteriorate kidney function and even induce acute renal failure. In this report we describe the first case of excessive tacrolimus intoxication caused by hypothyroidism. The patient had undergone single-lung transplantation 6 months earlier, developed hypothyroidism, and was admitted with acute anuric renal failure. Thyroxin is a potent activator of the cytochrome P-450- CYP 3A enzyme system, which is crucial for tacrolimus metabolism. Hence, hypothyroidism reduces cytochrome P-450 activity and may result in drug accumulation. Rapid reversal of toxic drug levels could be achieved by reducing drug intake and increasing thyroxin levels by substitution therapy. In conclusion, it is important to consider thyroid function when prescribing medications with a narrow therapeutic range, which are metabolized by the cytochrome P-450 system such as tacrolimus, and the possible devastating effect of impaired drug metabolism during hypothyroidism.

Clinical significance of renal biopsies showing concurrent acute rejection and tacrolimus-associated tubular vacuolization.

BACKGROUND: The clinical significance of biopsies showing both rejection and isometric tubular vacuolization has not been well defined in the literature. METHODS: The clinical picture, sequential histopathologic findings, and response to therapy were compared between 24 renal allograft biopsies showing both tubular vacuolization and rejection and 14 biopsies showing vacuolization alone. RESULTS: The rejection was categorized as grade 1 in 4/24 (16.6%), grade 2A in 10/24 (41.6%), and grade 2B in 10/24 (41.6%) cases (Banff schema, 1993-1995). Treatment with additional steroids and tacrolimus led to a decrease in the interstitial inflammation score (2.6+/-0.1 to 1.3+/-0.1, P<0.001), tubulitis score (2.6+/-0.1 to 1.1+/-0.1, P<0.001), and serum creatinine (4.4+/-2.2 mg/dl to 3.3+/-2.6 mg/dl, P=0.001). Complete response, partial response and no response to antirejection therapy were observed in 16/24 (66.7%), 3/24 (12.5%), and 5/24 (20.8%) patients, respectively. Although there was a rise in the plasma (1.4+/-0.2 ng/ml to 2.8+/-0.3 ng/ml, P<0.001) and whole blood (16.5+/-2.8 ng/ml to 31.2+/-5.7 ng/ml, P<0.001) tacrolimus levels, repeat biopsy showed no change in the size or extent of tubular vacuolization (mean score 2.88+/-0.19 vs. 2.83+/-0.21). The morphologic characteristics of the tubular vacuoles in these cases did not differ from those observed in 14 cases of tacrolimus nephrotoxicity not complicated by rejection. CONCLUSION: Patients with concurrent acute rejection and tubular vacuolization usually benefit from increased immunosuppression. The pathogenesis of the vacuolization in this clinical setting is not clear, but may reflect immune-mediated tubular injury.

Serious interaction between mibefradil and tacrolimus.

BACKGROUND/AIMS: Tacrolimus is metabolized by cytochrome P450 3A4 and 2D6 and has a narrow therapeutic range. We report a serious kinetic interaction between tacrolimus and mibefradil, a potent cytochrome P450 inhibitor. CASE REPORT: A 62-year-old women who had undergone liver transplantation was treated with tacrolimus for immunosuppression. For control of blood pressure, the patient was treated with nifedipine. She developed ankle edema, and nifedipine was replaced by mibefradil. Four days later, she presented with mental confusion, renal failure, and hyperglycemia, compatible with tacrolimus toxicity. In agreement with this assumption, the tacrolimus blood concentration was 100 ng/ml. Mibefradil and tacrolimus were both stopped, and the patient recovered within 1 week. Eight days after stopping mibefradil, tacrolimus was restarted at the same dosage and the subsequent plasma concentrations remained in the therapeutic range. CONCLUSIONS: Mibefradil increases the tacrolimus blood concentration by inhibiting its metabolism and should, therefore, not be used in patients treated with tacrolimus.

Tacrolimus (FK 506) overdose: a report of five cases.

INTRODUCTION: Tacrolimus (FK 506), a potent anti-T cell agent, has been shown to be effective in preventing the rejection of transplanted organs. Published research on tacrolimus has focused on effects associated with therapeutic use. Virtually no literature addresses the acute toxicity or the management of tacrolimus overdose. We report five cases of acute overdose with tacrolimus. CASE REPORTS: A 2-year-old female with no prior medical history ingested 10 mg of tacrolimus. She remained asymptomatic. A 2-year-old female with a history of multiple visceral organ transplants ingested 11 mg of her tacrolimus. She was admitted to the hospital and activated charcoal was administered. Her renal function was monitored and no changes were noted in a 24 h period. She was discharged. A 29-year-old male renal transplant patient took 150 mg of tacrolimus. He recovered with only a minimal creatinine elevation. A 23-year-old heart and lung transplant patient ingested 375 mg of tacrolimus. She had no effects from the overdose. A 34-year-old female experienced an acute/chronic overdose of 7-9 mg and remained asymptomatic. DISCUSSION: Tacrolimus is a neutral macrolide antibiotic that is extracted from the fermentation broth of the soil fungus Streptomyces tsukubaensis. Chronic oral dosing has been associated with numerous side effects. Although these patients ingested significant doses of tacrolimus, they suffered few toxic manifestations associated with tacrolimus. CONCLUSION: Little information is available regarding acute tacrolimus overdosage. In this small series of patients, tacrolimus did not produce acute physiologic incapacitation.