Can we undergo nasal polyp surgery while on antipsychotic drugs?

Hello doctor,

My father's dystonia started suddenly, and he has tremors and stiffness in his right hand. Also, his neck has been pulling backward continuously for two years. He is diagnosed with dystonia two years back, and he has been taking Pacitane 2 mg three tablets daily for two years. But in the past four months, he is hearing voices that a group of people are planning to kill him, and also, he has a suspicion. He was feeling restless and anxious. For three months, he has been taking Olapin 20 mg, Zaporil 25 mg (from 20 days), Ativan 1 mg, and Vertin 8 mg. His condition is improved a little bit now. So please tell me how long we have to continue the medication to cure his delusion and auditory hallucinations completely. What are the side effects it causes, and do these medications cause dementia? Please tell me, doctor, I am worried, and also my father has nasal polyps. He was advised long back to get the surgery done by an ENT doctor. So can we do that surgery now, as he is taking antipsychotic drugs?