Tacrolimus is a medication used as an immunosuppressant to prevent organ rejection after a transplant surgery. It belongs to the class of drugs called calcineurin inhibitors and works by suppressing the immune system to prevent it from attacking the transplanted organ.

Tacrolimus is used to prevent organ rejection in kidney, liver, and heart transplant patients. It is also available as a topical medication to treat certain skin conditions such as atopic dermatitis, eczema, and psoriasis.

Tacrolimus is available in different forms such as capsules, tablets, injections, and ointments. It is usually taken once or twice a day, as prescribed by a healthcare professional. The dose may be adjusted based on the patient's response to the medication and other factors.

Common side effects of tacrolimus include headaches, nausea, diarrhea, high blood pressure, and tremors. In some cases, it can cause more serious side effects such as kidney damage, infections, and certain types of cancer.