Optimal time for therapeutic drug monitoring of cyclosporine microemulsion in patients with psoriasis.

Background  The clinical usefulness of cyclosporine in patients with psoriasis has generally been established; however, modification of the dosage on the basis of therapeutic drug monitoring is needed to prevent potential adverse reactions. The area under the drug concentration–time curve from 0 to 4 h after treatment (AUC0−4), used to assess the pharmacokinetics of cyclosporine microemulsion, correlates with clinical symptoms and adverse reactions. Methods  In order to evaluate the blood collection times after oral treatment that are most relevant to pharmacokinetics, we examined the pharmacokinetics of cyclosporine up to 4 h after treatment in 24 patients with psoriasis vulgaris who received an oral dose of 3.0 mg/kg of cyclosporine microemulsion (Neoral®) daily in two divided doses. Results  Our results showed that the blood concentration of cyclosporine 2 h after treatment (C2) correlated with AUC0−4 (r = 0.89, P < 0.001). Conclusions C2 should be monitored in patients treated with cyclosporine microemulsion instead of the blood trough level immediately before treatment, which has conventionally been used to monitor cyclosporine concentrations in blood.