I worked in mental health for 20 years and worked closely with inpatient units during that time. The ONLY time I ever saw medications withdrawn was when a female patient was pregnant, and that was done with great trepidation, weighing the benefits and costs carefully.
Now, if the inpatient psychiatrist is going to start him on a radically different regimen that requires a washout period of his psychotropic meds, then you might see 48 hours without meds, but I never saw that done. To deprive a patient of his medications for 48 hours, unless it's medically necessary and pursuant to a rational plan, is really medical malpractice. Especially if the medications for his high blood pressure were denied.
First, I'd write a letter to the hospital administrator explaining, as briefly as you can, what happened with the denial of medications. Give dates and names of doctors. Don't issue any threats to sue them or go to the state licensing board (you can always do that later on if you wish), or you will get a highly defensive, well-couched response in legalese. You might still get a poor response. Doctors are more or less God in the medical profession, and the hospital will be loathe to piss them off.
If this hospital is your only practical choice, I feel for you. It might be sufficient just to raise awareness with the hospital administrator that things are going badly. If they are intelligent, they don't want to get sued or have you go to the state. They will probably have a talk with the relevant doctors and get to the bottom of it. You will never know what was said or the final outcome. As long as your son gets proper treatment in the future, that's really the most important point.
Best wishes to you and your son.