This study is about a drug called enoxaparin which is used to prevent or treat blood clots.
There are no studies about the use of this drug in obese adolescents and yet the
investigators use it to prevent clots when they have surgery at Children's National for
weight loss. The investigators hypothesis is that the obesity leads to increased kidney size
and faster drug clearance. Therefore the investigators think they might be underdosing these
adolescents. This study will check the drug levels at different points after the drug dose to
see whether the investigators are achieving the expected levels for prevention of clots.