The 28-day after-opening guideline applies only to compounding pharmacies, not to FDA-registered drug manufacturers like BPI, which produces your GLP-1 medication. Because BPI is a manufacturer, they assign a beyond-use date (BUD) based on validated stability and sterility data for the full duration of use - typically 3 months - even after the vial is punctured.
The vials are designed and tested for extended use as long as you:
Store your vial refrigerated between uses,
Use a new sterile needle for each injection, and
Do not expose the vial to contamination.
If you follow these instructions, your vial remains safe and effective for the full intended duration of your treatment plan.