Limited overdosage experience is available. Acute overdosages of up to 30 times the intended dose have been reported. Almost all cases have been asymptomatic and all patients recovered with no sequelae. Occasionally, acute overdosage has been followed by adverse reactions consistent with those listed in the ADVERSE REACTIONS section except in one case where transient urticaria and lethargy were observed. Based on the poor aqueous solubility and extensive erythrocyte and plasma protein binding, it is anticipated that tacrolimus is not dialyzable to any significant extent; there is no experience with charcoal hemoperfusion. The oral use of activated charcoal has been reported in treating acute overdoses, but experience has not been sufficient to warrant recommending its use. General supportive measures and treatment of specific symptoms should be followed in all cases of overdosage.
In acute oral and IV toxicity studies, mortalities were seen at or above the following doses: in adult rats, 52X the recommended human oral dose; in immature rats, 16X the recommended oral dose; and in adult rats, 16X the recommended human IV dose (all based on body surface area corrections).
NOTE: Anaphylactic reactions have occurred with injectables containing castor oil derivatives. See WARNINGS.
|Patient Population||Recommended Initial Oral Dosage a||Observed Whole Blood Trough Concentrations|
|a) Note: two divided doses, q12h|
|b) In a second smaller study, the initial dose of tacrolimus was 0.15 to 0.2 mg/kg/day and observed tacrolimus concentrations were 6 to 16 ng/mL during month 1 to 3 and 5 to 12 ng/mL during month 4 to 12 (see CLINICAL STUDIES).|
|Adult kidney transplant patients|
|In combination with azathioprine||0.2 mg/kg/day||month 1 to 3: 7 to 20 ng/mL|
|month 4 to 12: 5 to 15 ng/mL|
|In combination with MMF/IL-2 receptor antagonistb||0.1 mg/kg/day||month 1 to 12: 4 to 11 ng/mL|
|Adult liver transplant patients||0.10 to 0.15 mg/kg/day||month 1 to 12: 5 to 20 ng/mL|
|Pediatric liver transplant patients||0.15 to 0.20 mg/kg/day||month 1 to 12: 5 to 20 ng/mL|
It is recommended that patients initiate oral therapy with tacrolimus capsules if possible. If IV therapy is necessary, conversion from IV to oral tacrolimus is recommended as soon as oral therapy can be tolerated. This usually occurs within 2 to 3 days. The initial dose of tacrolimus should be administered no sooner than 6 hours after transplantation. In a patient receiving an IV infusion, the first dose of oral therapy should be given 8 to 12 hours after discontinuing the IV infusion. The recommended starting oral dose of tacrolimus capsules is 0.10 to 0.15 mg/kg/day administered in two divided daily doses every 12 hours. Coadministered grapefruit juice has been reported to increase tacrolimus blood trough concentrations in liver transplant patients. (See Drugs that May Alter Tacrolimus Concentrations).
Dosing should be titrated based on clinical assessments of rejection and tolerability. Lower tacrolimus dosages may be sufficient as maintenance therapy. Adjunct therapy with adrenal corticosteroids is recommended early post-transplant.
Dosage and typical tacrolimus whole blood trough concentrations are shown in the table above; blood concentration details are described in Blood Concentration Monitoring: Liver Transplantation below.
The recommended starting oral dose of tacrolimus (administered every 12 hours in two divided doses) is 0.2 mg/kg/day when used in combination with azathioprine or 0.1 mg/kg/day when used in combination with MMF and IL-2 receptor antagonist (see CLINICAL STUDIES). The initial dose of tacrolimus may be administered within 24 hours of transplantation, but should be delayed until renal function has recovered (as indicated for example by a serum creatinine ≤ 4 mg/dL). Black patients may require higher doses to achieve comparable blood concentrations. Dosage and typical tacrolimus whole blood trough concentrations are shown in the table above; blood concentration details are described in Blood Concentration Monitoring: Kidney Transplantation below.
The data in kidney transplant patients indicate that the Black patients required a higher dose to attain comparable trough concentrations compared to Caucasian patients.
|Time After Transplant||Caucasian n=114||Black n=56|
|Dose (mg/kg)||Trough Concentrations (ng/mL)||Dose (mg/kg)||Trough Concentrations (ng/mL)|
Pediatric liver transplantation patients without pre-existing renal or hepatic dysfunction have required and tolerated higher doses than adults to achieve similar blood concentrations. Therefore, it is recommended that therapy be initiated in pediatric patients at a starting IV dose of 0.03 to 0.05 mg/kg/day and a starting oral dose of 0.15 to 0.20 mg/kg/day. Dose adjustments may be required. Experience in pediatric kidney transplantation patients is limited.
Patients with Hepatic or Renal Dysfunction
Due to the reduced clearance and prolonged half-life, patients with severe hepatic impairment (Pugh ≥ 10) may require lower doses of tacrolimus. Close monitoring of blood concentrations is warranted.
Due to the potential for nephrotoxicity, patients with renal or hepatic impairment should receive doses at the lowest value of the recommended IV and oral dosing ranges. Further reductions in dose below these ranges may be required. Tacrolimus therapy usually should be delayed up to 48 hours or longer in patients with post-operative oliguria.
Conversion from One Immunosuppressive Regimen to Another
Tacrolimus should not be used simultaneously with cyclosporine. Tacrolimus or cyclosporine should be discontinued at least 24 hours before initiating the other. In the presence of elevated tacrolimus or cyclosporine concentrations, dosing with the other drug usually should be further delayed.
Blood Concentration Monitoring
Monitoring of tacrolimus blood concentrations in conjunction with other laboratory and clinical parameters is considered an essential aid to patient management for the evaluation of rejection, toxicity, dose adjustments and compliance. Factors influencing frequency of monitoring include but are not limited to hepatic or renal dysfunction, the addition or discontinuation of potentially interacting drugs and the post-transplant time. Blood concentration monitoring is not a replacement for renal and liver function monitoring and tissue biopsies.
Two methods have been used for the assay of tacrolimus, a microparticle enzyme immunoassay (MEIA) and ELISA. Both methods have the same monoclonal antibody for tacrolimus. Comparison of the concentrations in published literature to patient concentrations using the current assays must be made with detailed knowledge of the assay methods and biological matrices employed. Whole blood is the matrix of choice and specimens should be collected into tubes containing ethylene diamine tetraacetic acid (EDTA) anti-coagulant. Heparin anti-coagulation is not recommended because of the tendency to form clots on storage. Samples which are not analyzed immediately should be stored at room temperature or in a refrigerator and assayed within 7 days; if samples are to be kept longer they should be deep frozen at -20° C for up to 12 months.
Although there is a lack of direct correlation between tacrolimus concentrations and drug efficacy, data from Phase II and III studies of liver transplant patients have shown an increasing incidence of adverse events with increasing trough blood concentrations. Most patients are stable when trough whole blood concentrations are maintained between 5 to 20 ng/mL. Long-term post-transplant patients often are maintained at the low end of this target range.
Data from the U.S. clinical trial show that tacrolimus whole blood concentrations, as measured by ELISA, were most variable during the first week post-transplantation. After this early period, the median trough blood concentrations, measured at intervals from the second week to one year post-transplantation, ranged from 9.8 ng/mL to 19.4 ng/mL.
Therapeutic Drug Monitoring, 1995, Volume 17, Number 6 contains a consensus document and several position papers regarding the therapeutic monitoring of tacrolimus from the 1995 International Consensus Conference on Immunosuppressive Drugs. Refer to these manuscripts for further discussions of tacrolimus monitoring.
Data from a Phase 3 study of tacrolimus in conjunction with azathioprine indicate that trough concentrations of tacrolimus in whole blood, as measured by IMx®** were most variable during the first week of dosing. During the first three months of that trial, 80% of the patients maintained trough concentrations between 7 to 20 ng/mL, and then between 5 to 15 ng/mL, through 1 year.
In a separate clinical trial of tacrolimus in conjunction with MMF and daclizumab, approximately 80% of patients maintained tacrolimus whole blood concentrations between 4 to 11 ng/mL through 1 year post-transplant.
In another clinical trial of tacrolimus in conjunction with MMF and basiliximab, approximately 80% of patients maintained tacrolimus whole trough blood concentrations between 6 to 16 ng/mL during month 1 to 3 and, then, between 5 to 12 ng/mL from month 4 through 1 year.
The relative risks of toxicity and efficacy failure are related to tacrolimus whole blood trough concentrations. Therefore, monitoring of whole blood trough concentrations is recommended to assist in the clinical evaluation of toxicity and efficacy failure.
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