Methenamine hippurate may be effective for preventing UTI in patients without renal tract abnormalities, particularly when used for short-term prophylaxis. It does not appear to work in patients with neuropathic bladder or in patients who have renal tract abnormalities. The rate of adverse events was low, but poorly described.
There is a need for further large well-conducted RCTs to clarify this question, particularly for longer term use for people without neuropathic bladder.
Value of urinary prophylaxis with methenamine in gynecologic surgery.
There is a high risk of postoperative bacteriuria and urinary tract infection after gynecologic surgery. Postoperative asymptomatic bacteriuria often disappears without treatment, but 15-20% of patients still require treatment for postoperative urinary tract infection. This study was carried out to assess the value of prophylactic treatment with methenamine hippurate after routine gynecologic surgery.
                This was a prospective, randomized, double-blind, placebo-controlled clinical trial comprising 145 patients undergoing routine gynecologic laparotomy or vaginal plastic surgery using a Foley catheter for 24 h. Antibiotics were not used. Subjects received 1 g Hiprex or placebo twice daily for 5 days. Urine was cultured preoperatively, at catheter removal, and 2 days later. Patients with positive cultures were not given antibiotics unless they were symptomatic. The follow-up period was 1 month.
                The chi-square test, Fisher exact test, and t-test were used with level of significance at 0.05, and odds ratios with 95% confidence intervals were calculated.
                Asymptomatic bacteriuria was diagnosed in 36 cases (50.0%) in the placebo group and 22 cases (30.1%) in the methenamine group (p = 0.02). Urinary tract infection was diagnosed in 10 cases (13.9%) in the placebo group and two cases (2.7%) in the methenamine group (p = 0.03). There were few adverse events.
                Prophylactic treatment with methenamine hippurate significantly reduces the incidence of postoperative bacteriuria and urinary tract infection.