The only time a med has caused slurred speech was when I took too much once and when they caused night terrors and I was half awake, half asleep and trying to scream for help but it came out slurred like I was intoxicated. I have a bipolar family member who to my knowledge does not drink but nearly always sounds intoxicated and slurs......I think it’s from being over medicated big time. I hope you find a solution to this.