Hello

I am trying to use seemingly unrelated regressions (SUR) technique in a 2-level model which is presented below:

Code:
mixed Patient_reported_outcome Patient_reported_outcome_baseline $controls i.Wave i.Drug i.Hospital_ID i.Drug_Sequence, base || Patient_ID:, vce(robust)
How can I use SUR technique to account for a different outcome / dependent variable:

Code:
mixed Clinical_measure Clinical_measure_baseline $controls i.Wave i.Drug i.Hospital_ID i.Drug_Sequence, base || Patient_ID:, vce(robust)
Many thanks in advance!