Here’s an excerb from a site:
Creatine monohydrate is the most commonly available creatine supplement and the form primarily used in most research studies. However, other forms are available. Creatine phosphate is sold in small quantities. It is an extremely expensive form of creatine, which likely curtails its widespread distribution and use. Any effect of creatine phosphate ingested orally would be mediated by creatine alone, since gut phosphatase enzymes would readily cleave off the phosphate portion of the molecule, liberating FCr.
Additionally, serum possesses high phosphatase activity, leading to rapid breakdown of intravenously administered creatine phosphate to creatine and phosphate (Saks and Strumia 1993). Limited data suggest that PCr infusions may enhance physical training intensity (Clark 1996), and only a few published studies have used oral creatine phosphate to evaluate its effects on exercise performance or health. Creatine phosphate is used in various countries as an injectable drug primarily for medical reasons. However, as Clark (1996) notes, the use of intravenous PCr must be undertaken only under the guidance of a qualified physician.