DMSO can be part of a defined drug substance as well as a process solvent. Trametinib dimethyl sulfoxide, identified in the FDA prescribing information for MEKINIST, is a concrete example.
A solvate has a different purpose
In this example, DMSO belongs to the specified drug-substance form. It is not simply unwanted solvent left behind after drying. The identity and quality controls must correspond to that form and its approved product documentation.
This differs from a synthesis in which DMSO is used as a medium and then removed. In that situation, the remaining solvent is addressed through the product's residual-solvent control strategy.
Define the intended role before purchasing
For an intended solvate component, establish the applicable material and regulatory requirements with the pharmaceutical quality team. A supplier grade name alone does not qualify the material for that role.
For process-solvent use, specify the relevant reaction and impurity requirements separately from downstream residue limits. The two applications can involve the same chemical but answer different quality questions.
The trametinib example demonstrates a specific DMSO-containing drug substance. It does not establish a common solvent route for all anti-tumor medicines.