In some cases, if the combination product has the assembly on the high-level combination product itself, was reviewed and the primary mechanism of action was a device, then likely, CDRH (Center for Devices and Radiological Health) would have been the approving department. In that case, UDI would apply at the very top level. The device component would be exempt, however the UDI would be applied at the high-level assembly.
On the other hand, if the same combination product was reviewed by, for example CDR (Center for Drug Evaluation and Research), the product will most likely have a NDC (national drug code) number for the high level assembly. Inside of that could be a device component and other special rules categorizing the product as a single entity combination product may apply.
An example would be a transdermal patch that is placed on the surface of your skin. It has a drug component embedded within a physical device component. In that case, it is a single entity component and would require UDI only on the medical device part.
If a company is primarily a medical device manufacturer, they are aware of UDI requirements. Some pharma companies are now finding that some of their products may fall into this specialized category.
Many scenarios for medical device and drug components as combination products are nuanced and must be reviewed on an individual basis. Both the U.S. FDA and the European Commission have published guidelines about UDI applied to the medical device component inside a combination.
For a comprehensive overview on the definitions and requirements for UDI for combination products as defined by US FDA, see the following 16-minute episode of ‘Reed Tech Insights’.