You really don’t have the dose, then.
But I understand that this sometimes is all you got. And for some drugs the per kg is the important information. Here, I am with @schuemie’s “let’s just add a field”. This is a piece of information we cannot store right now without re-defining the content of other fields.
@Dymshyts: Can you put a proposal into the CDM Github? Something like “dose_per_kg” with allowable values NULL (usual) and Y.