Rx Only

WARNING

Increased susceptibility to infection and the possible development of lymphoma may result from immunosuppression. Only physicians experienced in immunosuppressive therapy and management of organ transplant patients should prescribe tacrolimus capsules. Patients receiving the drug should be managed in facilities equipped and staffed with adequate laboratory and supportive medical resources. The physician responsible for maintenance therapy should have complete information requisite for the follow-up of the patient.

DESCRIPTION
Tacrolimus Capsule is available for oral administration containing the equivalent of 0.5 mg, 1 mg or 5 mg of monohydrate 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 capsules. 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:

Tacrolimus has an empirical formula of C44H69NO12•H2O 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.

structure CLINICAL PHARMACOLOGY
Mechanism of Action
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.

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).

Pharmacokinetics
Tacrolimus activity is primarily due to the parent drug. The pharmacokinetic parameters (mean±S.D.) of tacrolimus have been determined