The pharmacokinetics of etanercept in healthy volunteers

OBJECTIVE: TO describe the pharmacokinetics of etanercept when administered by subcutaneous injection in single doses to healthy volunteers, METHODS: Twenty-six healthy volunteers between 19 and 50 years of age recei ved single doses of etanercept 25 mg by subcutaneous injection into the abd omen. Serial serum samples were collected for 21 days. An enzyme-linked imm unosorbent assay with a quantitation limit of 0.3 ng/mL was used to measure the drug concentrations. RESULTS: Etanercept was well tolerated by healthy volunteers. A one-compart ment model was found to best describe the concentration-time data and was u sed to determine the pharmacokinetic parameters. Etanercept is slowly absor bed from the site of injection with a time of peak concentration (+/- SD) o f 51 +/- 14 hours; peak concentration was 1.46 +/- 0.72 mg/L. The AUC was 2 35 +/- 98 mg.h/L, apparent clearance was 132 +/- 85 mL/h, apparent volume o f distribution was 12 +/- 6 L, and the half-life was 68 +/- 19 hours. CONCLUSIONS: Etanercept was slowly absorbed and slowly eliminated after sub cutaneous administration. Dosing at the recommended rate of 25 mg twice wee kly would be expected to result in concentrations of approximately 3 mg/L. Intersubject variability for apparent clearance in healthy volunteers was 6 4%.