Is it permissible for a schizophrenic patient, who is medically stable but suffers from medication side effects such as dry mouth and extreme fatigue, to break their fast in Ramadan, especially given that they cannot stop taking the medication?

It appears that the questioner is able to fast without harm, fearing neither an increase in illness nor a delay in recovery due to fasting, nor an unbearable hardship. Dryness of the throat can be alleviated by rinsing the mouth or performing ghusl. However, if the fatigue becomes severe and harm is feared, or if the hardship is unbearable, then you are permitted to break your fast.