I wouldn't administer progesterone until I was confident in how the hormone acts and all of it's side effects since it has a lot to do with not only when a bitch goes into heat but also plays a role in labor and tells the bitches body when to start producing milk. I don't know enough about the drug and how injecting can or will effect the natural progesterone. I wouldn't mess with it based on the accounts of my friends telling me Hey I used it and it worked! You might want to do more thorough research on it.