Tacrolimus

Definition

Tacrolimus belongs to a group of medicines known as immunosuppressive agents. It is used primarily to lower the body's natural immunity in order to prevent the rejection of organ transplants and to prevent graft-versus-host disease. Tacrolimus is also known as Prograf and FK506.

Purpose

Tacrolimus first saw use in transplant patients. By suppressing the activity of the immune system, tacrolimus makes it more likely that the recipient of a transplanted organ will accept that organ. It is especially used for kidney transplants.

In the fight against leukemia, grafts of stem cells from donors are sometimes given to the patient to encourage the blood of a recipient to begin production of normal cells. Tacrolimus may be given during the graft process because it seems to make the patient more receptive to the donated stem cells.

Description

Tacrolimus somehow suppresses, or prevents activity of, the cells in the lymphatic system, which are known as T cells. Under normal circumstances T cells mount an immune response to foreign materials in the body. However, during a transplant, T cells can cause the reaction that can lead to the rejection of a donor organ. The exact reason for the activity of tacrolimus is not understood.

Recommended dosage

Given by mouth, in a capsule, or by intravenous line, tacrolimus doses range from about 0.03 milligrams to 0.05 milligrams per kilogram (1 kilogram equals approximately 2.2 pounds) of body weight per day. Individuals with liver or kidney problems must be given a lower dose.

Precautions

Tacrolimus should be taken without food and long after a meal. If there is food in the stomach it will interfere with the way the drug makes its way into the body. Grapefruit juice can increase the activity of tacrolimus and should be avoided.

Side effects

Many serious side effects are associated with tacrolimus. Conditions affecting the brain brought on by the use of tacrolimus include coma (unconscious state) and delirium (uncontrolled and erratic conscious state). Most times the brain conditions are reversible. Headache, skin rashes, hair loss (alopecia), pain, sensitivity to light and shock (anaphylaxis) are all side effects. Kidney damage, which cannot be reversed, is also a danger.

Use of tacrolimus greatly increases the likelihood a person will get skin cancer and lymphoma. Anyone using the drug should be monitored closely for changes in the skin, and all normal precautions for avoiding skin cancer, such as avoiding direct exposure to ultraviolet light, should be taken.

Interactions

This drug interacts with a long list of other drugs. It is important to tell the physician in charge of the care plan, each and every drug being taken, so that interactions can be avoided. Tacrolimus prevents effective vaccination, and vaccinations should not be given while the drug is in use.

Diane M. Calabrese

Intravenous line

—A tube that is inserted directly into a vein to carry medicine directly to the blood stream bypassing the stomach and other digestive organs that might alter the medicine.

Lymphatic system

—The system that collects and returns fluid in tissues to the blood vessels and produces defensive agents for fighting infection and invasion by foreign bodies.

Stem cell

—Cell that gives rise to a lineage of cells. Particularly used to describe the most primitive cells in the bone marrow from which all the various types of blood cell are derived.