Detailed Drug Information:

DRUG CLASS AND MECHANISM: Tacrolimus is a drug that suppresses the immune system and is used to prevent rejection of transplanted organs. Tacrolimus accomplishes its immune-suppressing effecting by inhibiting an enzyme (calcineurin) crucial for the multiplication of T-cells, cells that are vital to the immune process. The use of oral tacrolimus allows transplantation specialists to reduce the dose of steroids which are also used to prevent rejection. This "steroid-sparing effect" is important because of the many side effects that can occur when larger doses of steroids are used for a long period of time. Tacrolimus was approved by the FDA in April, 1994 for liver transplantation and also has been used in patients for heart, kidney, small bowel, and bone marrow transplantation.

PREPARATIONS: Tacrolimus is available as 1mg and 5mg capsules. It also is available for intravenous use.

STORAGE: Tacrolimus should be stored at room temperature between 15° and 30°C (59° and 86°F).

PRESCRIBED FOR: Tacrolimus is used for the prevention of rejection of transplanted organs.

DOSING: Oral tacrolimus is taken twice daily. Doses vary widely and are based on blood tests that measure the amount of tacrolimus in the body. Taking tacrolimus with food can reduce some of the abdominal pain that can occur with this medicine; however, food can reduce the amount of tacrolimus that is absorbed. This is especially true with fatty foods. Thus, tacrolimus is best taken without food. If it must be taken with food, it should be taken with non-fatty food.

DRUG INTERACTIONS: The destruction of tacrolimus by the body may be inhibited by a large number of drugs, resulting in higher blood levels of tacrolimus, and possibly increasing its side effects. Such drugs include bromocriptine (Parlodel), cimetidine (Tagamet), cisapride (Propulsid), clarithromycin (Biaxin), cyclosporine (Sandimmune; Neoral), danazol (Danocrine), diltiazem (Cardizem; Tiazac), erythromycin, fluconazole (Diflucan), itraconazole (Sporanox), ketoconazole (Nizoral), metoclopramide (Reglan), methylprednisolone (Medrol), nicardipine (Cardene), troleandomycin (Tao), and verapamil (Calan; Isoptin; Verelan; Covera-HS). Grapefruit juice also may have a similar effect on tacrolimus and should be avoided.

Other drugs can stimulate the break-down of tacrolimus, decreasing its blood concentration and possibly reducing its effectiveness. Such drugs include carbamazepine (Tegretol), nifedipine (Procardia; Adalat); phenobarbital, phenytoin (Dilantin), rifabutin, and rifampin,

Live virus vaccines should be avoided while receiving tacrolimus or any other medicine that suppresses the immune system since the vaccines may be less effective.

Since tacrolimus can cause hyperkalemia (high potassium in the blood), the use of tacrolimus with diuretics that also cause retention of potassium is not recommended. Such diuretics include triamterene (found in Dyazide and Maxzide), amiloride (found in Moduretic), and spironolactone (Aldactone).

Aluminum hydroxide, which is found in many antacids, binds tacrolimus in the stomach. Aluminum-containing antacids should not be taken with tacrolimus.

PREGNANCY: Tacrolimus crosses the placenta, but there have been no adequate studies in pregnant women to assess the effects on the fetus. Among women who have received tacrolimus while pregnant, high potassium levels and kidney injury in newborns have been reported. Therefore, tacrolimus should be used during pregnancy only when it is clearly needed.

NURSING MOTHERS: Tacrolimus passes into breast milk. It is recommended that breast-feeding be discontinued while women are receiving oral tacrolimus.

SIDE EFFECTS: Tacrolimus is associated with many and various side effects. These include baldness (which can occur in 1 in 5 patients who take it), anemia (1 in 2), loss of appetite (1 in 3), diarrhea (3 of 4), high concentrations of potassium in the blood (1 in 2), high blood pressure (1 in 2), nausea (1 in 2), vomiting (1 in 4), tingling sensation in the extremities (2 in 5), itching (1 in 3), tremor (1 in 2), fever (1 in 2), headache (2 in 3), rash (1 in 4), high blood sugar concentrations (between 1 in 3 and 1 in 2), and abdominal pain (1in 4).

Other side effects may include confusion, painful joints, increased sensitivity to light, blurred vision, insomnia, infection, jaundice (yellowing of the skin due to effects on the liver), kidney injury, swollen ankles, and seizures.