Unfortunately, it seems to be limited , or to quote a great article from the Journal of Cosmetic Dermatology "topically applied ascorbyl phosphate salts are, at very best, poorly absorbed in comparison with AA"
Its a common experience that often points to something happening on a cellular level
[PMID: 21771450] PubMed record related to this compound for laboratory literature review
Journal (World Journal of Gastroenterology, Jan 7, 2022, 28(1), 2346)
While affordability matters, safety and authenticity of the injections should never be compromised
Research-only note: Cagrilintide is not FDA-approved for therapeutic use