What Is Tacrolimus?

Tacrolimus is a calcineurin inhibitor immunosuppressant medication used primarily to prevent organ rejection in patients who have received a liver, kidney, or heart transplant. It is one of the most widely used anti-rejection drugs in transplant medicine. Tacrolimus is also available as a topical ointment (Protopic) for treating moderate to severe atopic dermatitis (eczema).

Brand-name versions include Prograf (immediate-release capsules), Astagraf XL (extended-release capsules), Envarsus XR (extended-release tablets), and Protopic (topical ointment). Generic versions of the oral formulations are widely available.

Tacrolimus is also used off-label for conditions such as lung transplant rejection, graft-versus-host disease, Crohn's disease, ulcerative colitis, lupus nephritis, and myasthenia gravis.

How does Tacrolimus work?

Tacrolimus works by binding to a protein called FKBP-12 (FK506 binding protein) inside immune cells. This Tacrolimus-FKBP-12 complex then inhibits calcineurin, an enzyme that is essential for activating T-cells — a type of white blood cell responsible for attacking foreign tissue. By blocking calcineurin, Tacrolimus prevents the production of interleukin-2 and other cytokines that drive the immune response, effectively suppressing the body's ability to reject a transplanted organ.

For transplant patients, this immune suppression is critical to keeping the new organ functioning. The trade-off is an increased susceptibility to infections and certain cancers, which is why careful monitoring and dose adjustments based on blood levels are required.

What doses are available for Tacrolimus?

• Immediate-Release Capsules (Prograf): 0.5 mg, 1 mg, 5 mg
• Extended-Release Capsules (Astagraf XL): 0.5 mg, 1 mg, 5 mg
• Extended-Release Tablets (Envarsus XR): 0.75 mg, 1 mg, 4 mg
• Oral Granules for Suspension (Prograf): 0.2 mg, 1 mg packets
• Injectable Solution (Prograf): 5 mg/mL
• Topical Ointment (Protopic): 0.03%, 0.1%

How hard is it to find Tacrolimus in stock?

Tacrolimus has a findability score of 35 out of 100, meaning it can be moderately difficult to locate in stock at your local pharmacy. While Tacrolimus is not currently listed on the FDA's active drug shortage list, intermittent supply disruptions have been reported at individual pharmacies — particularly for specific generic manufacturers or certain strengths and formulations. The IV formulation has historically been more prone to shortages than oral forms. If your pharmacy is out of stock, try calling other nearby pharmacies or use Medfinder to search availability in your area.

Who Can Prescribe Tacrolimus?

Tacrolimus is primarily prescribed by specialists experienced in immunosuppressive therapy and organ transplant management, including:

• Transplant Surgeons
• Transplant Nephrologists (kidney transplant)
• Transplant Hepatologists (liver transplant)
• Transplant Cardiologists (heart transplant)
• Dermatologists (for the topical ointment Protopic)
• Rheumatologists (off-label uses)
• Gastroenterologists (off-label for Crohn's disease or ulcerative colitis)

Due to its serious side-effect profile and the need for therapeutic drug monitoring, Tacrolimus should only be prescribed by physicians experienced in managing transplant patients or immunosuppressive therapy.

Is Tacrolimus a controlled substance?

No, Tacrolimus is not a controlled substance. It does not have a DEA schedule and is not considered to have potential for abuse or dependence. However, it is a prescription-only medication that requires regular blood level monitoring and careful dose adjustments, so it cannot be obtained over the counter.

Common Side Effects of Tacrolimus

Tacrolimus can cause a range of side effects. The most commonly reported include:

• Tremors — shaking of the hands, which is dose-related
• Headache
• Diarrhea
• Nausea and abdominal pain
• High blood pressure (hypertension)
• Kidney function changes (elevated creatinine)
• High blood sugar — new-onset diabetes after transplant (NODAT)
• High potassium levels (hyperkalemia)
• Low magnesium levels (hypomagnesemia)
• Insomnia
• Hair loss

Serious side effects include nephrotoxicity (kidney damage), neurotoxicity, increased risk of infections (BK virus, CMV), and an increased risk of lymphoma and skin cancers. Tacrolimus carries an FDA boxed warning about these risks. Report any unusual symptoms to your transplant team immediately.

Alternative Medications to Tacrolimus

If Tacrolimus is unavailable or not suitable for you, your transplant team may consider the following alternatives:

• Cyclosporine (Neoral, Sandimmune, Gengraf) — Another calcineurin inhibitor used for transplant rejection prophylaxis. An older agent with a different side-effect profile that may cause more cosmetic side effects like excessive hair growth and gum overgrowth.
• Sirolimus (Rapamune) — An mTOR inhibitor immunosuppressant with a different mechanism. May be used when calcineurin inhibitor toxicity (especially kidney damage) is a concern.
• Everolimus (Zortress) — Another mTOR inhibitor approved for kidney and liver transplant rejection. Often used in combination with reduced-dose Tacrolimus to spare kidney function.
• Belatacept (Nulojix) — A selective T-cell costimulation blocker given as an IV infusion for kidney transplant patients. Used as an alternative to calcineurin inhibitors to avoid nephrotoxicity.

Important: Never switch immunosuppressant medications on your own. Any changes must be supervised by your transplant team to prevent organ rejection.

Drug Interactions with Tacrolimus

Tacrolimus has significant drug interactions that can be dangerous. Key interactions include:

• Strong CYP3A4 inhibitors (Ketoconazole, Itraconazole, Voriconazole, Posaconazole, Clarithromycin) — Significantly increase Tacrolimus blood levels, raising toxicity risk
• Strong CYP3A4 inducers (Rifampin, Phenytoin, Carbamazepine, St. John's Wort) — Significantly decrease Tacrolimus levels, risking organ rejection
• Cyclosporine — Must not be used together due to additive nephrotoxicity
• Live vaccines — Should be avoided due to immunosuppression
• Other nephrotoxic drugs (Aminoglycosides, Amphotericin B, NSAIDs) — Additive kidney damage risk
• Potassium-sparing diuretics, ACE inhibitors, ARBs — Increased risk of dangerous hyperkalemia
• Grapefruit and grapefruit juice — Can significantly increase Tacrolimus levels; avoid completely

Always inform your transplant team and pharmacist about all medications, supplements, and herbal products you are taking.

Final Thoughts on Tacrolimus

Tacrolimus is a cornerstone immunosuppressant medication that has dramatically improved outcomes for organ transplant recipients since its introduction. While it carries significant risks — including kidney damage, increased infection susceptibility, and cancer risk — it remains one of the most effective anti-rejection drugs available.

If you're having trouble finding Tacrolimus in stock at your pharmacy, Medfinder can help you locate it nearby. With a findability score of 35, some patients do experience difficulty finding specific strengths or formulations. Generic immediate-release Tacrolimus is the most widely available version, starting around $30–$65 with discount coupons. Brand-name formulations like Prograf, Astagraf XL, and Envarsus XR are more expensive but may be covered with insurance or manufacturer copay assistance programs.

Never miss a dose or switch formulations without your transplant team's approval — even small changes in Tacrolimus blood levels can lead to organ rejection or toxicity.