“…However, tacrolimus has several serious side effects, including renal toxicity, neurotoxicity, diabetes, and hypertension. In clinical applications, tacrolimus often exhibits toxicity or rejection within the specified treatment concentration range for the following reasons: it covers a narrow therapeutic window, its pharmacokinetics and pharmacodynamics differ among individuals, and it lacks a close correlation between dosage and serum concentration; as a result, clinical treatment becomes difficult (Henry, 1999;Sperschneider et al, 2001;Margreiter et al, 2002;Ghio et al, 2004). For the most efficient immunosuppressant treatment and to reduce adverse reactions, patients who take tacrolimus after receiving organ transplants should have routine therapeutic drug monitoring.…”