Cystitis First-line treatment of uncomplicated cystitis is nitrofurantoin 100 mg orally twice a day for 5 days (it is contraindicated if creatinine clearance is < 60 mL / min), trimethoprim / sulfamethoxazole (TMP / SMX) 160/800 mg orally twice a day for 3 days, or fosfomycin 3 g orally once.