Tacrolimus (Page 6 of 9)

7.11 Others

Bromocriptine, nefazodone, metoclopramide, danazol, ethinyl estradiol, amiodarone and methylprednisolone may inhibit CYP3A metabolism of tacrolimus and increase tacrolimus whole blood concentrations. Monitoring of blood concentrations and appropriate dosage adjustments of tacrolimus are recommended when these drugs and tacrolimus are co-administered.

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

Pregnancy Category C-There are no adequate and well-controlled studies in pregnant women. Tacrolimus is transferred across the placenta. The use of tacrolimus during pregnancy in humans has been associated with neonatal hyperkalemia and renal dysfunction. Tacrolimus given orally to pregnant rabbits at 0.5 to 4.3 times the clinical dose and pregnant rats at 0.8 to 6.9 times the clinical dose was associated with an increased incidence of fetal death in utero, fetal malformations (cardiovascular, skeletal, omphalocele, and gallbladder agenesis) and maternal toxicity. Tacrolimus should be used during pregnancy only if the potential benefit to the mother justifies the potential risk to the fetus.

In pregnant rabbits, tacrolimus at oral doses of 0.32 and 1.0 mg/kg, 0.5 to 4.3 times the clinical dose range (0.075 to 0.2 mg/kg) based on body surface area, was associated with maternal toxicity as well as an increased incidence of abortions. At the 1 mg/kg dose, fetal rabbits showed an increased incidence of malformations (ventricular hypoplasia, interventricular septal defect, bulbous aortic arch, stenosis of ductus arteriosis, interrupted ossification of vertebral arch, vertebral and rib malformations, omphalocele, and gallbladder agenesis) and developmental variations. In pregnant rats, tacrolimus at oral doses of 3.2 mg/kg, 2.6 to 6.9 times the clinical dose range was associated with maternal toxicity, an increase in late resorptions, decreased numbers of live births, and decreased pup weight and viability. Tacrolimus, given orally to pregnant rats after organogenesis and during lactation at 1.0 and 3.2 mg/kg, 0.8 to 6.9 times the recommended clinical dose range was associated with reduced pup weights and pup viability (3.2 mg/kg only); among the high dose pups that died early, an increased incidence of kidney hydronephrosis was observed.

8.3 Nursing Mothers

Tacrolimus is excreted in human milk. As the effect of chronic exposure to tacrolimus in healthy infants is not established, patients maintained on tacrolimus should discontinue nursing taking into consideration importance of drug to the mother.

8.4 Pediatric Use

The safety and efficacy of tacrolimus in pediatric kidney transplant patients have not been established. Successful liver transplants have been performed in pediatric patients (ages up to 16 years) using tacrolimus. Two randomized active-controlled trials of tacrolimus in primary liver transplantation included 56 pediatric patients. Thirty-one patients were randomized to tacrolimus-based and 25 to cyclosporine-based therapies. Additionally, a minimum of 122 pediatric patients were studied in an uncontrolled trial of tacrolimus in living related donor liver transplantation. Pediatric patients generally required higher doses of tacrolimus to maintain blood trough concentrations of tacrolimus similar to adult patients [see Dosage and Administration (2.2)].

8.5 Geriatric Use

Clinical trials of tacrolimus did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

8.6 Use in Renal Impairment

The pharmacokinetics of tacrolimus in patients with renal impairment was similar to that in healthy volunteers with normal renal function. However, consideration should be given to dosing tacrolimus at the lower end of the therapeutic dosing range in patients who have received a liver and have pre-existing renal impairment. Further reductions in dose below the targeted range may be required [see Dosage and Administration (2.3) and Clinical Pharmacology (12.3)].

8.7 Use in Hepatic Impairment

The mean clearance of tacrolimus was substantially lower in patients with severe hepatic impairment (mean Child-Pugh score: >10) compared to healthy volunteers with normal hepatic function. Close monitoring of tacrolimus trough concentrations is warranted in patients with hepatic impairment [see Clinical Pharmacology (12.3)].

The use of tacrolimus in liver transplant recipients experiencing post-transplant hepatic impairment may be associated with increased risk of developing renal insufficiency related to high whole-blood trough concentrations of tacrolimus. These patients should be monitored closely and dosage adjustments should be considered. Some evidence suggests that lower doses should be used in these patients [see Dosage and Administration (2.3) and Clinical Pharmacology (12.3)].

10 OVERDOSAGE

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. Acute overdosage was sometimes followed by adverse reactions consistent with those listed in Adverse Reactions (6) (including tremors, abnormal renal function, hypertension, and peripheral edema); in one case of acute overdosage, 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, 52 times the recommended human oral dose; in immature rats, 16 times the recommended oral dose; and in adult rats, 16 times the recommended human IV dose (all based on body surface area corrections).

11 DESCRIPTION

Tacrolimus capsules are available for oral administration containing 0.5 mg, 1 mg or 5 mg of tacrolimus. Inactive ingredients include lactose monohydrate, hypromellose E5, croscarmellose sodium, and magnesium stearate. The 0.5 mg capsule shell contains gelatin, titanium dioxide, iron oxide yellow and sodium lauryl sulfate, the 1 mg capsule shell contains gelatin, titanium dioxide and sodium lauryl sulfate, and the 5 mg capsule shell contains gelatin, titanium dioxide, iron oxide red and sodium lauryl sulfate.

Tacrolimus, previously known as FK506, is the active ingredient in tacrolimus. Tacrolimus is a macrolide immunosuppressant produced by Streptomyces tsukubaensis. Chemically, tacrolimus is designated as [3S -[3R *[E (1S *,3S *,4S *)], 4S * ,5R *,8S * ,9E ,12R *, 14R *, 15S *,16R *,18S *,19S *,26aR *]]–5,6,8,11,12,13,14,15,16,17,18,19,24,25,26,26a-hexadecahydro-5,19-dihydroxy-3-[2-(4-hydroxy-3-methoxycyclohexyl)-1-methylethenyl]- 14,16-dimethoxy-4,10,12,18-tetramethyl-8-(2-propenyl)-15,19-epoxy-3H-pyrido[2,1-c ] [1,4] oxaazacyclotricosine- 1,7,20,21 (4H,23H)-tetrone, monohydrate.

The chemical structure of tacrolimus is:

Chemical Structure

Tacrolimus has an empirical formula of C44 H69 NO12 •H2 O and a formula weight of 822.03. Tacrolimus appears as white crystals or crystalline powder. It is practically insoluble in water, freely soluble in ethanol, and very soluble in methanol and chloroform.

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Tacrolimus inhibits T-lymphocyte activation, although the exact mechanism of action is not known. Experimental evidence suggests that tacrolimus binds to an intracellular protein, FKBP-12. A complex of tacrolimus-FKBP-12, calcium, calmodulin, and calcineurin is then formed and the phosphatase activity of calcineurin inhibited. This effect may prevent the dephosphorylation and translocation of nuclear factor of activated T-cells (NF-AT), a nuclear component thought to initiate gene transcription for the formation of lymphokines (such as interleukin-2, gamma interferon). The net result is the inhibition of T-lymphocyte activation (i.e., immunosuppression).

Tacrolimus prolongs the survival of the host and transplanted graft in animal transplant models of liver, kidney, bone marrow, small bowel and pancreas, lung and trachea, skin, cornea, and limb.

In animals, tacrolimus has been demonstrated to suppress some humoral immunity and, to a greater extent, cell-mediated reactions such as allograft rejection, delayed type hypersensitivity, collagen-induced arthritis, experimental allergic encephalomyelitis, and graft versus host disease.

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