Simulated median profiles (continuous lines), 95% prediction intervals (broken lines) and observed mean data ± SD 6-MP plasma concentration data (filled circles and line bars) in children. i.v.(−), intravenous dosing without allopurinol; i.v.(+), intravenous dosing with allopurinol; p.o.(−), oral dosing without allopurinol; p.o.(+), oral dosing with allopurinol 5,24