It's a trap

Seeing how Veron's grip loosened significantly, Andrew made use of the opportunity to run as fast as he could away from him before the pain would subside and whatever effect the drug had on him would kick in.

What he didn't realize was that the drug he injected into Veron had the exact opposite effect on him. Instead of suppressing his werewolf form and giving strength to his vampire form, it suppressed his vampire form, giving strength to his werewolf form. 

Just after the pain subsided, Veron's body bent without his control and his bones began to crack as he painlessly shifted into his wolf form, something he had not done since he returned from the mating ceremony.

Just as soon as the transition was complete, he chased after Andrew, caught up with him in mere seconds, and clawed the side of his face.