My mom was hallucinating in the rehab center because she was on meds there to settle her down. That was 2 weeks ago. Now she's home and she isn't having the hallucinations anymore. I hope this helps a little.
Sometimes its pretty quick, other times meds are metabolized slow so it could be a week or so. But, if it gets worse rather than better or persists much after that, have another look medically at what else might be going on.