My mom is on a ton of medications and they can definitely have side effects in certain combinations. The thing is....there are so many different meds and so many combinations of them, doctors don't even know what can happen. They do know that some meds aren't compatible with others but when you are on a dozen of them it can be confusing. My wife's uncle (RIP) was a happy guy but as his health failed he got on one med after another and eventually had 16. He needed heart surgery and had to drop all his meds for a period of time before his surgery. For awhile there he was back to his fun loving old self.