Nothing that fascinating about the ingredients. From
wiki
* Potassium nitrate (5% )
* Sodium fluoride (0.15 W/V Fluoride Ion)
* Strontium chloride - creates a barrier around the Dentin
* Strontium acetate - creates a barrier around the Dentin
* Potassium chloride - nerve calming
I doubt this would have the same numbing effect if used in other areas of the body, but I could be wrong.
Looking at the ingredients, Potassium nitrate (saltpeter) has many uses, from fireworks to stump remover preparations, a preservative etc. Apparently, it has not been conclusively shown that it does reduce dentine hypersensitivity (wiki). We all know Sodium fluoride. What some people might not know is when it's swallowed, around half is converted by HCl in the stomach to the very toxic hydrofluoric acid!!
Strontium chloride and strontium acetate reduce hypersensitivity by forming a barrier over the exposed nerve endings in the dentine due to gum recession - not sure how this would go in other body cavities

Potassium chloride is important for nerve and heart function among other things. Can't see how this how this would aid in rectum numbing though, and although I have some KCl, I'm not in any hurry to see if it does
As for diversion to drug manufacture, I can't see why this would be so. KNO3 might have some uses in making nitrites, which can be used in certain routes, but there are far more abundant sources than the 5% in this preparation.
This all seems very odd, like we're missing an essential clue
