Worsening Dry Mouth Problem

I am a female, age 68. Dry mouth is making my life a whole lot less livable. When it began (I remember noticing it as I was gardening), I was unconcerned, but it gets worse and worse. My doctor (Kaiser) says simply, "Yes, 25 percent of older people have it." A doctor friend prescribed a medication that stimulates saliva but also sweat and causes diarrhea (since I was unprepared for this pop-up, I cannot remember the name). So I am wondering if there is any cause other than the benzodiazepenes and gabapentin that I have taken for decades.