A treatment window for the intravenous treatment of wounds, including thermal and chemical burns, with cP12 is presented. In particular, Applicants have unexpectedly found that delaying intravenous treatment with fibronectin-derived peptides, such as cP12, from 2 to 6 hours, particularly about 4 hours, after wounding, provides superior wound-closing results than treatment at 1 hour or after 8 or more hours.