Many medication cause dry mouth ( pretty much all meds do) dry mouth leads to very dry lips ... mine use to crack and bleed .. finally saw a dermatologist and they blamed it on my meds .. also saw my dentist and he said it was from my medications also . since i cant just stop the medications i just am never more than 20 feet from my chapstick .haha I have them all over the house ..

Good Luck and hope you can find something to soothe the chapped lips