In "The Fix", Dr. Natalie Lambert discovers that a drug used on cattle, lidovuterine-B, has the effect of reversing the effects of vampirism: when treated, Nick's blood does not boil in sunlight. She proceeds to inject him with a small dose of the drug, with apparently miraculous results. Nick is able to go out in broad daylight with impunity and eat solid food.
Unfortunately, the effects do not last long; and it rapidly becomes apparent that Nick's body is adapting to the drug. It takes ever larger doses to have the same effect. Furthermore, there are side effects on his personality. Natalie therefore refuses to continue to treat him with lidovuterine; and, although he initially objects to her decision, Nick eventually has to agree with her.