The comparability of etanercept pharmacokinetics in healthy Japanese and American subjects.

Thirty Japanese (J) and 32 American (A) healthy subjects received single doses of etanercept by subcutaneous injection, in 3 separate trials. Serum samples were collected for 480 hours after dosing. Concentrations were determined using enzyme-linked immunosorbent assay methods. Pharmacokinetic parameters were calculated using both non-compartmental and compartmental methods. Etanercept was slowly absorbed, with mean+/-SD time to maximum serum concentration of 47+/-15 hours (J), and 51+/-20 hours (A). The maximum serum concentration and area under the concentration time curve increased for doses 10 mg, 25 mg, and 50 mg, in a linear relationship. Etanercept was slowly eliminated, with observed mean+/-SD half-life of 80+/-25 hours (J) and 75+/-15 hours (A) and mean+/-SD apparent clearance of 144+/-65 mL/h (J) and 132+/-74 mL/h (A). Very low concentrations of etanercept were observed in the urine samples collected in the Japanese subjects. All adverse reactions observed resolved without issue, and none required discontinuation from the study.