Avoid taking an antacid or anti-diarrhea medicine within 1 hour before or after you take hyoscyamine, methenamine, methylene blue, phenyl salicylate, and sodium biphosphate. Antacids or anti-diarrhea medicine can make it harder for your body to absorb hyoscyamine.
If you also take ketoconazole (Nizoral), wait at least 2 hours after taking it before you take hyoscyamine, methenamine, methylene blue, phenyl salicylate, and sodium biphosphate.
