Dosing is based on the trimethoprim component - the suspension contains trimethoprim 8 mg/ml.
Since this is a multi-ingredient drug, Cerner cannot handle ordering by mg/kg.
You will occasionally get questions about this, usually from the ER.
As a workaround, it is possible to order in PowerChart and PharmNet as ml/kg.
Use this calculator to verify appropriate weight-based dosing: