I need some guidance.

This is regarding my father 65M. He is diagonal with chronic hypertension and diabetes. 1.5 months ago, he was diagnosed with NPH for which they placed a VP shunt in his brain after which his symptoms got better (included imbalance, urinary incontinence, gait issues etc)

Around 2 weeks ago he had an episode of delirium, where he started speaking gibberish, got extremely angry, repeating the same thing over and over again. Later he developed hallucinations, which lasted for three days in which, he did not sleep at all. We had him admitted in the hospital, they checked for infections, dehydration, repeated his CT Scans, did all the other tests which could tell why his symptoms were occurring but everything was normal. He was discharged and prescribed quetiapine 25mg twice daily. His delirium, speaking gibberish and hallucinations disappeared and everything was great for around one week.

Now recently, starting this morning, he has again started speaking gibberish which eventually leads to him getting agitated and angry. We have been in and out of the hospital for the past whole month.

I want to ask if it is something to do with this antipsychotic that he's taking ? There's no chance he can develop resistance to it this early. Any help will be appreciated as I am his youngest daughter and it's extremely disturbing for me to see him turn into someone I don't know.