Tacrolimus

Tacrolimus is an immunosuppressive drug primarily used to prevent organ rejection in transplant patients. It belongs to the macrolide class of drugs and functions by inhibiting the activity of T-lymphocytes, which play a crucial role in immune response. Tacrolimus is available in various forms, including oral capsules, ointments, and injectable solutions.

Indications

-Organ Transplantation: Tacrolimus is most commonly used to prevent rejection of transplanted organs, such as the liver, kidney, or heart. -Autoimmune Diseases: It is sometimes used off-label for the treatment of autoimmune conditions, such as lupus nephritis, severe eczema (atopic dermatitis), and rheumatoid arthritis, when other treatments have failed.

Dosage

Kidney transplantation : 0.2mg/kg/day in adults as two divided doses taken every 12 hrs. Liver transplantation : 0.10-0.15mg/kg/day in two divided doses taken every 12 hrs. Maintenance dosage should be individualized so as to maintain whole blood concentration between 5-20ng/ml Children : Generally need doses 1.5 to 2 times greater than those in adults.

Contra-Indications

-Hypersensitivity: Tacrolimus is contraindicated in patients with known hypersensitivity to the drug or any of its components. -Breastfeeding: It is contraindicated for use in breastfeeding mothers due to potential risks to the infant. -Pregnancy: Should be used with caution and only if the potential benefits justify the risks.

Special Precautions

-Renal Impairment: Tacrolimus can be nephrotoxic, so patients with pre-existing kidney conditions require careful monitoring. -Liver Impairment: Patients with liver impairment may require dosage adjustments due to altered metabolism of the drug. -Infections: Patients on tacrolimus are at increased risk of infections due to immunosuppression. Regular monitoring for signs of infection is necessary. -Diabetes: Tacrolimus can induce or worsen diabetes; blood glucose levels should be regularly monitored.

Side Effects

-Common: Tremors, headache, diarrhea, high blood pressure, hyperkalemia, hyperglycemia, and nephrotoxicity. -Serious: Increased risk of infections, nephrotoxicity, neurotoxicity (e.g., seizures, confusion), and hypertension. -Topical Use: Burning sensation at the application site, skin irritation, and increased risk of skin infections.

Drug Interactions

-Cytochrome P450 Inhibitors: Drugs like ketoconazole, erythromycin, and diltiazem can increase tacrolimus levels and risk of toxicity. -Cytochrome P450 Inducers: Rifampin, phenytoin, and carbamazepine can decrease tacrolimus levels, reducing its efficacy. -Other Immunosuppressants: Concurrent use with other immunosuppressive agents may increase the risk of infection or lymphoma. -NSAIDs: Can increase the risk of kidney damage when used with tacrolimus.