For doses of ACTEMRA 4 mg per kg given every 4 weeks, the predicted mean (± SD) steady-state AUC, Cmin and Cmax of tocilizumab were 13000 ± 5800 mcg∙h per mL, 1.49 ± 2.13 mcg per mL, and 88.3 ± 41.4 mcg per mL, respectively. The accumulation ratios for AUC and Cmax were 1.11 and 1.02, respectively. The accumulation ratio was higher for Cmin (1.96). Steady-state was reached following the first administration for Cmax and AUC, respectively, and after 16 weeks Cmin.

For doses of ACTEMRA 8 mg per kg given every 4 weeks, the predicted mean (± SD) steady-state AUC, Cmin and Cmax of tocilizumab were 35000 ± 15500 mcg∙h per mL, 9.74 ± 10.5 mcg per mL, and 183 ± 85.6 mcg per mL, respectively. The accumulation ratios for AUC and Cmax were 1.22 and 1.06, respectively. The accumulation ratio was higher for Cmin (2.35). Steady-state was reached following the first administration and after 8 and 20 weeks for Cmax, AUC, and Cmin, respectively. Tocilizumab AUC, Cmin and Cmax increased with increase of body weight. At body weight at or above 100 kg, the predicted mean (± SD) steady-state AUC, Cmin and Cmax of tocilizumab were 55500 ± 14100 mcg∙h per mL, 19.0 ± 12.0 mcg per mL, and 269 ± 57 mcg per mL, respectively, which are higher than mean exposure values for the patient population. Therefore, ACTEMRA doses exceeding 800 mg per infusion are not recommended [see Dosage and Administration (2.1)].

Systemic Juvenile Idiopathic Arthritis

The pharmacokinetics of tocilizumab were determined using a population pharmacokinetic analysis on a database composed of 75 patients with SJIA treated with 8 mg per kg (patients with a body weight at or above 30 kg) or 12 mg per kg (patients with a body weight less than 30 kg), given every 2 weeks. The predicted mean (± SD) AUC2 weeks, Cmax and Cmin of tocilizumab were 32200 ± 9960 mcg∙hr per mL, 245 ± 57.2 mcg per mL and 57.5 ± 23.3 mcg per mL, respectively. The accumulation ratio for Cmin (week 12 over week 2) was 3.2 ± 1.3. Steady state was reached on or after week 12. Mean predicted TCZ exposure parameters were similar between the two dose groups defined by body weight.

Distribution

Following intravenous dosing, tocilizumab undergoes biphasic elimination from the circulation. In rheumatoid arthritis patients the central volume of distribution was 3.5 L and the peripheral volume of distribution was 2.9 L, resulting in a volume of distribution at steady state of 6.4 L.

In pediatric patients with SJIA, the central volume of distribution was 0.94 L, the peripheral volume of distribution was 1.60 L resulting in a volume of distribution at steady state of 2.54 L.

Elimination

The total clearance of tocilizumab is concentration-dependent and is the sum of the linear clearance and the nonlinear clearance. The linear clearance was estimated to be 12.5 mL per h in RA and 7.1 mL per h in pediatric patients with SJIA in the population pharmacokinetic analysis. The concentration-dependent nonlinear clearance plays a major role at low tocilizumab concentrations. Once the nonlinear clearance pathway is saturated, at higher to