I've been on methenamine for years. I started with two tablets per day, along with two capsules of D-Mannose (over the counter). After three years, my doctors & myself believe the methenamine was adversely affecting my kidneys, so they cut me back to only half a tablet once per day (P.M.) and one D-Mannose once per day (A.M.). So far, so good. Because of other immune issues a month ago, I had my first interstitial cystisis flare since 2019 and no bladder infections at all. I hope the drug(s) will help you as much as they have me. Good luck!