It is an immunosuppressive drug whose main use is after allogenic organ transplant to reduce the activity of the patient's immune system and so the risk of organ rejection.

It is also used in a topical preparation in the treatment of severe atopic dermatitis (often called "eczema"), as have cyclosporin and azathioprine with much less success. It has also been used after bone marrow transplants and for severe refractory uveitis. It is also prescribed for the treatment of the skin condition, vitiligo.

History
Tacrolimus was discovered in 1987 by a Japanese team headed by T. Goto, T. Kino and H. Hatanaka; it was the first macrolide immunosuppressant discovered.Like ciclosporin, it was found in a soil fungus, although it is produced by a type of bacteria, Streptomyces tsukubaensis.The name tacrolimus is reportedly derived from 'Tsukuba macrolide immunosuppressant'.

The drug is owned by Astellas Pharma Inc. (Merging of Fujisawa Pharmaceutical Co.,Ltd. and Yamanouchi Pharmaceutical Co., Ltd as of April 1, 2005) and is sold under the tradename Prograf®. It is sometimes referred to as FK-506, an early name relating to its action. It was first approved by the Food and Drug Administration (FDA) in 1994 for use in liver transplantation, this has been extended to include kidney, heart, small bowel, pancreas, lung, trachea, skin, cornea, and limb transplants.

Pharmacology
Tacrolimus is a macrolide antibiotic. It reduces peptidyl-prolyl isomerase activity by binding to the immunophilin FKBP-12 (FK506 binding protein) creating a new complex. This FKBP12-FK506 complex interacts with and inhibits calcineurin thus inhibiting both T-lymphocyte signal transduction and IL-2 transcription.Although this activity is similar to ciclosporin, studies have shown that the incidence of acute rejection is reduced by tacrolimus use over ciclosporin.

Indications

Immunosuppresion following transplantation
It has similar immunosuppressive properties to ciclosporin, but is much more potent in equal volumes. Also like ciclosporin it has a wide range of adverse interactions, including that with grapefruit which increases plasma-tacrolimus concentration. Immunosuppression with tacrolimus was associated with a significantly lower rate of acute rejection compared with ciclosporin-based immunosuppression (30.7% vs 46.4%) in one study.

Dermatological use
As a cream (Protopic®), tacrolimus is a recent addition in the treatment of eczema, particularly atopic eczema. It suppresses inflammation in a similar way to steroids, but is not as powerful. An important advantage of tacrolimus is that unlike steroids, it does not cause skin thinning (atrophy). It may therefore be used continuously on the body and applied to the thinner skin over the face. On other parts of the body, topical steroids are generally a better treatment, and considerably cheaper.

Contraindications and Precautions
breast-feeding
ocular exposure
polyoxyethylated castor oil hypersensitivity
acute bronchospasm
Black patients
cardiac disease
cardiomyopathy
children
diabetes mellitus
electrolyte imbalance
exfoliative dermatitis
fungal infection
heart failure
hepatic disease
herpes infection
hyperglycaemia
hyperkalemia
hypertension
hypotension
ichthyosis
immunosuppression
infants
infection
intravenous administration
lymphoma
mononucleosis
neoplastic disease
occlusive dressing
oliguria
pregnancy
QT prolongation
renal disease
renal failure
renal impairment
seizure disorder
seizures
skin cancer
sunlight (UV) exposure
vaccination
varicella
viral infection

Side effects

From oral and intravenous administration
Side effects can be severe and include blurred vision, liver and kidney problems (it is nephrotoxic), seizures, tremors, hypertension, hypomagnesemia, diabetes mellitus, hyperkalemia, itching, insomnia, confusion, loss of appetite, hyperglycaemia, weakness, depression, cramps, and neuropathy, as well as potentially increasing the severity of existing fungal or infectious conditions such as herpes zoster or polyoma viral infections.

From topical use
A common side effect of tacrolimus ointment, if used over a wide area, is to cause a burning or itching sensation on the first one or two applications.

Cancer risks
Further information: Eczema#Immunomodulators
Tacrolimus and a related drug for eczema (pimecrolimus) were suspected of carrying a cancer risk, though the matter is still a subject of controversy. The FDA issued a health warning in March 2005 for the drug, based on animal models and a small number of patients. Until further human studies yield more conclusive results, the FDA recommends that users be advised of the potential risks. Whereas current practice by UK dermatologists is not to consider this a significant real concern and they are increasingly recommending the use of these new drugs.

Dermatologists agree that the drug should be used as a second-line remedy only after conventional methods of treatment have failed.

Source: wikipedia GFDL

Medic8® Medicines

Page last modified: May 2007