Great question! Yes — there are several databases that look at drug–drug similarity and interaction beyond just chemical structure. You’re right about STITCH — it focuses on chemical–chemical and chemical–protein interactions. You might also want to check out:

DrugBank – includes detailed drug–drug interactions and target info.

ChEMBL – good for bioactivity-based similarity.

DrugComb or DrugRepV2 – focus more on drug synergy and similarity in pharmacological profiles.

Each has a slightly different angle, so combining data from a few of them usually gives the best picture.