Hi,
No, thankfully, it is not common practice and hopefully never will be. These injections are very stressful and the animals are doomed to shorter lives. Another member discovered a batch recently, read
HERE. There is also mention of morphing at the bottom of this
page.
Hope this answers any questions. They do look kind of cool but part of my original interest in axolotls was peaked when I learned that they remained in larval form. My stand is if you want a morphed version, there are many other sals who do this naturally.