Severe prolonged tacrolimus overdose with minimal consequences.

A 59-year-old man inadvertently received a 10-fold increase in his twice-daily oral dose of tacrolimus 1 mg that resulted in trough blood levels above 90 ng/ml for over a week. The patient had end-stage renal disease secondary to diabetes mellitus and had received a kidney transplant from his daughter 3 months earlier. Despite the numerous adverse effects commonly reported with tacrolimus, such as mild nephrotoxicity, nausea, tremors, and elevated liver enzyme levels, our patient's acute but prolonged overdose resulted in minimal signs and symptoms of toxicity.