How long does haldol (haloperidol) stay in system?

7.5 days to 6 months. The half-life of Haldol (haloperidol) can vary from 1.5 days to more than 30 days, especially in those taking Haldol (haloperidol) decanoate, the long acting injectable form, once a month. It takes 4-5 half-lives to remove 94-97% of the drug concentration from the bloodstream. Therefore, it may take 7 1/2 days to 5 months or longer to remove it from the system.