Public domain werebeast transformation method:
Created by Lorenzo Cameron in 1942, this only known ingredient in this serum is the blood from a coyote (which Doctor Cameron mistakenly identified as a wolf). This blood is added to a mixture of unknown composition, and injected into the blood of the victim.
Very shortly after injection, the transformation begins with the victim becoming groggy, then falling unconscious (thinking they are falling asleep). While unconscious, they change into the werecoyote, and is over within a minute. It is slowest the first time. Later, it will be almost instantaneous.
The victim's hair changes color to match that of the fur of the animal the blood was taken from, they gain long pointed teeth that will eventually jut out from the mouth like tusks, their face becomes covered in hair, their nails grow into claws, and they gain superhuman strength. Their running speed may increase slightly, but not to superhuman levels.
While under the direct effects of Cameron's serum, the victim will be in a constant state of stress, putting them in fight or flight mode. They will run if they can, and will kill anyone who gets too close and threatens them too much.
An antidote must be injected for the transformation to wear off without more permanent effects on the victim. If the victim is unable to be given the antidote, the transformation will eventually fade on its own, but the victim will still experience the mental and behavioral issues that came with it, and will continue to transform.
Those under the effect of the serum seem to be compelled to roam at night, despite their fear, and always return back to where they first transformed, even if they were brought a great distance away.
After the antidote is administered, the victim remembers their actions while transformed as nightmares. They will also experience similar nightmares of roaming and attempting to kill people after the transformation *even if they haven't actually done anything*. Like the initial transformation, the antidote works within moments of being injected, reversing the transformation.
Doctor Cameron's plan for creating this serum was to use his servant, Petro, as an unknowing murder weapon by transforming him and setting him loose on the scientists who had laughed Cameron out of academia.
His excuse for creating it was that he wanted to give the formula to the United States government to create unstoppable supersoldiers with.
From the 1942 movie The Mad Monster, which is public domain. It's on youtube, tubi, the Internet Archive, and will soon be readable as my novelization once I finish editing it.